Veterinary Equine Education

equine veterinary education American Edition OctoBER 2019 • Volume 31 • NumbER 1 0

AAEP NEWS In this issue contents Crossing the line...... III

AAEP launches mentorship program to help create vibrant and sustainable careers...... IV

Ascend new heights in equine practice at 65th Annual Convention...... VI

Highlights of Recent Clinically Relevant Papers S. WRIGHT...... 506

Editorial Professional wellness of the veterinary team N. ENDENBURG and M. JOHNSTON...... 508

Case Reports Rostral mandibulectomy for treatment of a sarcoma in a 16-year-old Thoroughbred mare M. KÖHLER, M. KOENE, E.-C. SCHLIEWERT, H. AUPPERLE and H.-R. KRAUSE...... 510

Multifocal discrete osteolysis in a horse with silicate associated osteoporosis R. ZAVODOVSKAYA, M. ECKERT, B. G. MURPHY, S. M. STOVER, A. KOL and S. DIAB...... 517

Head and neck abscessation and thrombophlebitis following cheek tooth extraction in a pony A. A. HORBAL, R. J. M. REARDON, T. FROYDENLUND, R. C. JAGO and P. M. DIXON...... 523

Suspected case of hypersplenism as a cause of anaemia, thrombocytopenia and leucopenia in a Miniature Horse gelding R. E. RUBY, D. M. WONG, B. A. SPONSELLER and M. YAEGER...... 530

Successful surgical debridement of a cerebral Streptococcus equi equi abscess by parietal bone flap craniotomy in a 2-month-old Warmblood foal B. BROUX, T. VAN BERGEN, S. SCHAUVLIEGE, Y. VALI, L. LEFÈRE and I. GIELEN...... 538

Clinical Commentaries Hypersplenism E. DAVIS...... 535

Metastatic abscessation and other potential complications following strangles F. M. WHITLOCK, J. R. NEWTON and A. S. WALLER...... 539

Original Articles Comparison between radiography and computed tomography for diagnosis of equine skull fractures C. P. CRIJNS, R. WELLER, L. VLAMINCK, F. VERSCHOOTEN, S. SCHAUVLIEGE, S. E. POWELL, H. J. J. VAN BREE and I. M. V. L. GIELEN...... 543

Behavioural assessment of pain in 66 horses, with and without a bit W. R. COOK and M. KIBLER...... 551

Marketplace ...... 560A-D

Advertisers’ Index...... 529

Marketplace Advertisers’ Index...... 537

Cover photo by Dr. Nat White. American Association of Equine veterinary education Equine Practitioners American Edition 4033 Iron Works Parkway Lexington, KY 40511 OCTOBER 2019 • Volume 31 • Num ber 10 TEL (800) 443-0177 • (859) 233-0147 FAX (859) 233-1968 EMAIL [email protected] Editor (UK) Assistant Editors aaep.org T. S. Mair, BVSc, PhD, DEIM, DESTS, F. Andrews S. Love D. Archer M.L. Macpherson To access our website, go to aaep.org, select DipECEIM, MRCVS LOGIN, then enter your email and password. If you F.T. Bain M.J. Martinelli have difficulty logging in or have forgotten your Editors (USA) A.R.S. Barr I.G. Mayhew password, please call or email the office. N. A. White II, DVM A. Blikslager M. Mazan W. D. Wilson, MRCVS M. Bowen C.W. McIlwraith AAEP Officers N. Cohen B. McKenzie Jeff Berk, VMD, President Deputy Editors V. Coudry R. Moore Y. Elce A. Dart M. Oosterlinck David Frisbie, DVM, President-Elect P.R. Morresey J.-M. Denoix A. Parks Scott Hay, DVM, Vice President P.A. Wilkins T. Divers S. Puchalski Lisa Metcalf, DVM, Treasurer P. Dixon C. Riggs Margo Macpherson, DVM, Immediate Past President Management Group W. Duckett H. Schott D. Foley B. Dunkel J. Schumacher AAEP Staff T. S. Mair S. Dyson S. Semevelos David Foley, CAE, Executive Director N. A. White T. Fischer J. Slater D. Freeman B. Sponseller [email protected] W. D. Wilson T. Greet C. Sweeney Lori Rawls, Director of Finance & Operations J. L. N. Wood [email protected] R. Hanson H. Tremaine P. Harris K. Wareham Sally J. Baker, APR, Director of Marketing Management Board & Public Relations • [email protected] M. Hillyer S. Weese A. R. S. Barr P. Smith Keith Kleine, Director of Industry Relations M. Holmes R. Weller [email protected] D. Foley N. A. White (US Editor) N. Hudson C. Yao D. Mountford S. White Nick Altwies, Director of Membership P. Johnson [email protected] T. S. Mair (Editor) W. D. Wilson (US Editor) P.T. Khambatta Ex-officio S. E. Palmer J. L. N. Wood (Chairman) J.-P. Lavoie J. Cooney Kevin Hinchman, Director of Information Technology [email protected]

Karen Pautz, Director of Education Equine Veterinary Education is a refereed educational journal designed to keep the practicing veterinarian up to [email protected] date with developments in equine medicine and surgery. Submitted case reports are accompanied by invited reviews Sadie Boschert, Student Programs Coordinator of the subject (satellite articles) and clinical quizzes. Tutorial articles, both invited and submitted, provide in-depth [email protected] coverage of issues in equine practice.

John Cooney, Publications Coordinator Equine Veterinary Education (American Edition ISSN 1525-8769) is published monthly by the American [email protected] Association of Equine Practitioners, an international membership organization of equine veterinarians. Office of Giulia Garcia, Communications Coordinator publication is 4033 Iron Works Parkway, Lexington, KY 40511. Periodicals Postage paid at Lexington, KY and [email protected] additional mailing office. POSTMASTER: Send address changes to: Equine Veterinary Education, 4033 Iron Works Parkway, Lexington, KY 40511. Megan Gray, Member Concierge [email protected] Communications regarding editorial matters should be addressed to: The Editor, Equine Veterinary Education, Dana Kirkland, Sponsorship & Advertising Mulberry House, 31 Market Street, Fordham, Ely, Cambridgeshire CB7 5LQ, UK. Telephone: 44 (0) 1638 720250, Coordinator • [email protected] Fax: 44 (0) 1638 721868, Email: [email protected]. Katie McDaniel, EDCC Communication Manager All manuscript submissions for the journal should be submitted online at http://mc.manuscriptcentral.com/eve. Full [email protected] instructions and support are available on the site and a user ID and password can be obtained on the first visit. If you Deborah Miles, CMP, Trade Show Coordinator require assistance, click the Get Help Now link that appears at the top right of every ScholarOne Manuscripts page. [email protected] All subscription inquiries should be addressed to: Subscriptions Department, AAEP, 4033 Iron Works Parkway, Jayson Page, Office Manager Lexington, KY 40511, Telephone: (859) 233-0147, Email: [email protected]. Subscription rates: AAEP annual [email protected] membership dues include $40 for a subscription to Equine Veterinary Education. Other subscriptions at $151.80. Single copies $37.50. Paul Ransdell, Senior Development Officer [email protected] Canadian Subscriptions: Canada Post Corporation Number 40965005. Send change address information and Carey Ross, Scientific Publications Coordinator blocks of undeliverable copies to IBC, 7485 Bath Road, Mississauga, ON L4T 4C1, Canada. [email protected] © World copyright by Equine Veterinary Journal Ltd 2019. Pam Shook, Foundation Programs Coordinator [email protected] The authors, editors and publishers do not accept responsibility for any loss or damage arising from actions or Sue Stivers, Executive Assistant decisions based or relying on information contained in this publication. Responsibility for the treatment of horses [email protected] under medical or surgical care and interpretation of published material lies with the veterinarian. This is an aca- demic publication and should not be used or interpreted as a source of practical advice or instruction. Amity Wahl, Communications & Technology Coordinator The American Association of Equine Practitioners cannot accept responsibility for the quality of products or ser- [email protected] vices advertised in this journal or any claim made in relation thereto. Every reasonable precaution is taken before Kristin Walker, Membership & Event advertisements are accepted, but such acceptance does not imply any form of recommendation or approval. Services Coordinator [email protected] All companies wishing to advertise in Equine Veterinary Education, American edition, must be current AAEP exhibitors. AAEP retains the right, in its sole discretion, to determine the circumstances under which an exhibitor may advertise in this Elaine Young, Convention & Meetings Coordinator journal. While all advertisers must comply with applicable legal guidelines, Compounding Pharmacies are specifically [email protected] directed to limit themselves to pharmacy practices as dictated by the FDA Center for Veterinarian Medicine, Compliance Policy Guideline (www.fda.gov/ora/compliance_ref/cpg/cpgvet/cpg608-400.html). Advertising any complete or partial Published monthly. Deadlines are the mimicry of drugs and dosage forms of FDA approved formulations will not be accepted. Compounding Pharmacies, or any seventh of the preceding month. other exhibitors/advertisers who violate this rule in any fashion, will render their advertising contract null and void. Address advertising inquiries to Dana Kirkland (859) 233-0147 / [email protected] As a private organization, the AAEP reserves the right to exclude any company from advertising in Equine Veterinary Education, American edition, for any reason. The signing and delivery of the advertising contract shall AAEP Mission Statement: To improve the health and constitute an offer subject to acceptance by the AAEP. In its sole and absolute discretion, the AAEP may revoke its welfare of the horse, to further the professional acceptance of the advertising contract or may terminate any contract by delivery of written notice, in which event development of its members, and to provide resources the AAEP shall have no liability to the advertiser for damages for any other remedy. and leadership for the benefit of the equine industry. Printed by: Cenveo Publisher Services, Lancaster Division, Lancaster, PA. ETHICS AAEP News October 2019 III

Crossing the line By Kenton Morgan, DVM, DACT

We are all aware of the connotation of the phrase Veterinary Examiners and provided the same information “crossing the line.” When we cross the line, we have regarding these individuals practicing in West Virginia broached some type of rule, regulation or social norm. An without a license. The Kentucky board responded that issue recently came before the Professional Conduct and they had no jurisdiction to act because this was occurring Ethics Committee that quite literally, as well as figurative- in another state. ly, illustrates an example of crossing the line. Since this veterinarian is an AAEP member, the An AAEP member reported to the committee that several Professional Conduct and Ethics Committee was veterinarians were going into a neighboring state on an approached. Unfortunately, this member was unwilling to infrequent but regular basis and doing dental work, file a member-on-member complaint, the appropriate diagnosing and treating lameness, and providing other recourse for this type of accusation per our AAEP policy veterinary services. This occurs every day but, in this cir- and procedures; rather, they preferred to address it with cumstance, the veterinarians were not licensed in the the offending veterinarians themselves. The veterinarian neighboring state. The veterinarians, all from Kentucky, did not want to jeopardize referral services for their were practicing without a license in West Virginia. (This is clients, since one of the offending veterinarians was from also an issue with some racetrack veterinarians from a large referral practice. Pennsylvania and Maryland coming into West Virginia and working at the tracks despite not being licensed in I bring this situation to our attention not to illustrate West Virginia). what appears to be a rather dysfunctional state regulatory office but to remind all of us that we can do better when it comes to crossing the line. Just because we don’t get caught or there do not appear to be consequences for an illegal act (practicing without a license) does not lessen our obligation to abide by the rules. Besides being an

Shutterstock.com obvious violation of a state practice act, it also constitutes a blatant disregard of professional courtesy and respect for our colleagues.

As AAEP members, we have agreed to a standard of ethical practice that includes (but is not limited to): understand and comply with the laws, regulations and standard of care of the appropriate jurisdiction.

This example demonstrates a disregard by a few AAEP members for the regulations in West Virginia and demonstrates a lack of respect for their colleagues who are willing to abide by those same regulations. If we look at Presumably, this should be easily addressed by the West the foundations of professional ethics, particularly within Virginia Board of Veterinary Medicine (WVBVM). The veterinary medicine, one of the fundamental tenants of West Virginia practitioner inquired with the board our ethical principles is to treat others the way we would whether these specific veterinarians were licensed in West want to be treated. In this instance, I don’t think any of Virginia—and they were not. Even after providing docu- us would want unlicensed practitioners coming into our mentation that this was occurring, the board said they state and practicing veterinary medicine. had no jurisdiction and couldn’t do anything about it. Furthermore, a representative of the board stated that Let’s do our best to not cross the line. they did not have the resources or interest from the attorney general’s office to pursue such infractions. If you have an ethical question or issue to discuss, please join the Ethics Talk Rounds at communities.aaep.org/ This was certainly a frustrating situation for the reporting home. You can post your questions or comments anony- veterinarian, who then contacted the Kentucky Board of mously.

Dr. Morgan is managing veterinarian with Zoetis’ Equine Technical Services group and chair of the AAEP’s Professional Conduct and Ethics Committee. IV AAEP News October 2019 Association

AAEP launches mentorship program to help create vibrant and sustainable careers

To help young equine veterinarians successfully navigate a one-year term; both parties will need to opt back into equine practice and find lasting professional fulfillment, the relationship for it to continue. If one or both parties the AAEP has launched Outrider, a mentorship program elect not to renew the relationship, each can return to the that facilitates the creation of relationships between early- pool and receive a new match. career AAEP members and members with more experience. If you are a veteran practitioner and would like to volunteer as a mentor to a new practitioner, register as a mentor at jobs.aaep.org/ementor. You will then create your mentor profile by uploading your CV or work samples.

If you are in your first five years of practice and would like to find a mentor, register as a mentee at jobs.aaep.org/ The goal of the program is to provide mentorship in the ementor. After uploading your CV or work samples, you non-clinical areas of equine practice that are critical to will be able to review a list of volunteer mentors and their long-term success and wellbeing, such as general career background before requesting an engagement. You’ll advice and supportive interpersonal relationships. The negotiate and set expectations for time commitment up intent is not to provide specific case management advice. front so you both get the most value from your interac- tions. The exact nature of the relationship between mentors and mentees will be up to the pair; however, the majority of If you have questions about this new benefit, conversations will likely consist of phone calls, emails and/ contact Megan Gray, AAEP member concierge, at or text messages at least on a monthly basis. Pairings have [email protected] or (859) 233-0147.

We talked to your clients. 6,000 owners and trainers told us what makes a great veterinarian.

Touch tools and resources will give you:

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touch.aaep.org Association AAEP News October 2019 V

5 things to know about AAEP this month

1. Secure your spot in one of 2. The pre-registration 3. The AAEP Foundation 4. Five promising young 5. Join the more than 1,000 the few remaining open lab deadline for childcare at recently awarded more than researchers shared in members discussing offerings at the annual the annual convention is $700,000 in grants in nearly $100,000 in grants veterinary and industry convention by registering as Nov. 11. Register your support of equine welfare for from the AAEP Foundation topics in the AAEP Member soon as possible at child(ren) at convention. the second consecutive year. for projects addressing Vet Talk Facebook group. convention.aaep.org or aaep.org/childcare. important equine health Search for the group and (859) 233-0147. issues. click “Join.”

On air: Listen to new AAEP Practice Life, EVE and EVJ podcasts

Discover how establishing good relations In the Equine Veterinary Education podcast, Dr. Gigi Kay with your clients’ farriers can lead to discusses the paper “Locally invasive melanoma in the healthier horses and healthier practices on internal laminae of the hoof of a bay mule”; and Dr. the newest episode of the AAEP Practice Apryle Horbal discusses the paper “Head and neck absces- Life podcast. sation and thrombophlebitis following cheek tooth extraction in a pony.” Download or listen to the 31-minute The 43-minute episode, entitled “Developing a Positive episode at equineveterinaryeducation.podbean.com. Veterinarian-Farrier Relationship” is hosted by Dr. Mike Pownall and features conversations with Drs. Andrea In the EVJ in Conversation podcast, Dr. David Bardell Dube, Bibi Freer and Josh Zacharias, who dispense advice talks about the article “Differences in plasma and for developing rapport with farriers. Download or listen at peritoneal fluid proteomes identifies postential biomarkers podcast.aaep.org. associated with survival following strangulating small intestinal disease”; and Dr. Michelle Delco discusses the In addition, new episodes of the Equine Veterinary article “Intra-articular anaesthesia of the equine stifle Education podcast and EVJ in Conversation podcast offer improves foot lameness.” Download or listen to the deeper looks into papers recently published. 28-minute episode at evj.podbean.com.

MEMBERSHIP

Welcome new members, and congratulations recent graduates

New Members: Rocky Joe Terry, DVM, Glen Rose, TX Sarah Balik, DVM, Clermont, IA Leah Jo Toombs-Ruane, DVM, Saint Paul, MN Katharine Christie, DVM, DACVIM, Lexington, KY Paul Esteban Vega, MV, Navasota, TX Ryan DePaul, DVM, Alturas, CA Ashley Wegmann, DVM, Delmar, IA Sandra Diaz Yucupicio, DVM, Chino Hills, CA Rebecca Whitlock, DVM, Miller, SD Graham Stewart Fowke, DVM, Narberth, Dyfed, United Kingdom Kendra Gansz, DVM, Corydon, IA Recent Graduates: Ashton Wade Hammond, DVM, Wakarusa, IN Nicole Bricker, DVM, Aubrey, TX Stephenie Hoke, DVM, Fort Collins, CO Rhonda E. Hull, DVM, Gillette, WY Andrea Hoover, DVM, Shippensburg, PA Whitney Jones, DVM, Fort Plain, NY Samantha Hui, DVM, Sha Tin, New Territories, Hong Kong Diane Elizabeth Lewis, DVM, Galveston, TX Melissa Kelson, DVM, Mount Arlington, NJ Avery Frances Loyd, DVM, Manhattan, KS Hannah Jo Kingsley, DVM, Wheatland, ND Jesha Marcy-Quay, DVM, The Plains, VA Emily Lantzsch, DVM, Fayetteville, PA Kara Mauch, DVM, Harvey, ND Brittany Martabano, DVM, Fort Collins, CO Jamie Neufeld, DVM, Saskatoon, SK, Canada Joannes Paulus Melgar B, DVM, Panama, Panama Delaney Patterson, DVM, Dover, NH Rosemary Nicoletta, DVM, Walsenburg, CO Sierra Philipp, DVM, Guthrie, OK Fernanda Panis, DVM, Weatherford, TX Taryn Schairer, DVM, Elgin, IL Michael D. Pavsek, VMD, Fort Collins, CO Melissa S. Sheppard, DVM, Reidsville, NC Caroline Pouliot, DVM, Warwick, QC, Canada Eleanor Squires, DVM, Keswick, VA Betsy Malecha Price, DVM, Deer Lodge, MT Kathryn Storm, DVM, Keyser, WV Sarah Raabis, DVM, Madison, WI Hunter G. Wallace, DVM, Clever, MO Rhet Schultz, DVM, Prineville, OR Adriana Wilford, VMD, Lebanon, NJ VI AAEP News October 2019

Ascend new heights professionally and personally at the AAEP’s 65th Annual Convention. A robust educational program will help you administer the latest science-backed solutions to patients. Also take advantage of sessions and resources to strengthen your emotional resilience so that you can live your best life as well as opportunities to establish beneficial connections with your colleagues and veterinary suppliers.

Headliners Acquire a thorough understanding of and ability to communicate the treatment options available for horses with major bone and joint injuries when renowned equine orthopedic surgeon Dr. Dean W. Richardson delivers the Frank J. Milne Lecture, “The Tao of Equine Fracture Repair.” Dr. Richardson will convey the surgical opportunities for fracture repair and the associated importance of improving emergency management and refining surgical techniques. Sponsored by Platinum Performance.

Against the timely backdrop of rapidly changing demographics in the equine Dr. Dean Richardson veterinary profession, author, executive and communications consultant Tammy Hughes will address the central factors that drive gender-related communication problems while emphasizing the importance of men and women valuing each other’s strengths during her keynote address, “GenderSpeak: Working Together Successfully.” Sponsored by Merck Animal Health.

Learn from others

Use the experiences of others to help you navigate the daily rigors of life in equine practice at new AAEP Practice Life Conversations. Three facilitated discussions on the following Tammy Hughes topics will run concurrently from 3:00-5:00 p.m. on Dec. 7:

• Managing Emergency Coverage in a One-or Two-Doctor Practice • Planning for Maternity Leave • Creating a Culture of Wellness in Practice

No advance registration is necessary; just show up for the topic that is of most interest to you and add your own experiences to the discussion.

65th Annual Convention & Trade Show December 7-11, 2019 | Denver, Colorado

Laugh out loud

They say laughter is the best medicine. At Vet Story Night, on Dec. 8 from 8:00-11:00 p.m., revel in colleagues’ humorous stories about life, horses, clients and fellow practitioners. A cash bar will be available Break a sweat throughout the Don’t just exercise your mind at convention; exercise duration of this your body, too, during morning CrossFit and yoga hilarious fundraiser classes from 6:30-7:00 a.m. on Dec. 9-10 at the Hyatt for the AAEP Foundation. Purchase your advance Regency. If running is more your speed, sign up for the reserve seat for $35 with your convention registration. AAEP Denver 5K Running Tour at 6:30 a.m. on After Dec. 6, any remaining seating will be available for Dec. 9. More than 100 convention-goers participated $50. Sponsored by Merck Animal Health. each of the last two years. The group-oriented run offers four different paces, including a walking group. Register at cityrunningtours.com/aaepdenver2019. The running Enjoy a concert tour and fitness classes are sponsored by KindredBio. Create Mile High memories as the convention’s social calendar Bring the kids culminates with the After Party & Concert on Dec. 10 from Parenthood shouldn’t stand between you and your 7:30-10:00 p.m. Enjoy the camara- continuing education. AAEP has arranged affordable derie of colleagues during the first and safe childcare on-site at the convention center so hour before country music hitmaker you can enjoy Mile High family time. Childcare is Josh Turner takes the stage for an available for children between the ages of six months unforgettable concert. and 12 years for $25 per child for each morning or Complimentary beer and wine will be available from afternoon session block. The pre-registration deadline is 7:30-8:30 p.m., and a cash bar will be available Nov. 11. Visit convention.aaep.org/childcare to learn throughout. Sponsored by Zoetis. more or to register. In addition, a private and comfortable nursing mothers’ room will be available near session rooms each day of the convention. Sponsored by Boehringer Ingelheim.

Get started with the convention app Place the entire meeting in the palm of your hand with the AAEP Convention App. Browse sessions and speakers, create a personal itinerary and take notes; search, filter and contact exhibitors; create your own profile and message other attendees; swap ideas, photos and lessons learned with other attendees; view and post to the event stream on Twitter; and access the Proceedings papers closer to the event. Search “AAEP Education” at the App Store or Google Play to download. Sponsored by Zoetis. VIII AAEP News October 2019 CONtINUING EDUCATION

Mix business and pleasure at 2020 Resort Symposium in Aruba

horses from the threat of infectious and contagious 22nd AnnuAl ResoRt symposium disease.

Half-day sessions will leave plenty of time to bask in the sun, sand and sea. Or, enjoy the camaraderie of colleagues while exploring the island during optional group excursions that include horseback riding across the dunes, ARuBA UTV expedition to the caves and other secluded parts of January 23-25, 2020 the island, kayaking at the legendary Spanish Lagoon, island exploration in an air-conditioned vehicle and a catamaran snorkel sail.

Acquire 15 hours of midwinter CE while indulging in a Visit aaep.org/meetings/resort-symposium for more tropical paradise at the AAEP’s 22nd Annual Resort information about group excursions, including days, Symposium, which will be held Jan. 23–25, 2020, on the times and cost. Register for group excursions when you Caribbean island of Aruba. register for the meeting. You can also book your hotel and view the educational program on the site. Three half-day educational sessions led by Drs. Stephanie Caston, John Hubbell and Tracy Norman will boost your Thanks to Boehringer Ingelheim and IDEXX for their ability to administer effective sedation and restraint; triage, sponsorship support treat and manage field emergencies; provide preventative of the 22nd Annual care for neonates and geriatric horses; and protect client Resort Symposium.

INDUSTRY

AAEP Educational Partner Profile: Merck Animal Health

With a commitment to the Science of Healthier Animals™, Merck Animal Health works for you—and for horses. Backed by more than 70 years of innovation, the equine vaccine portfolio is known for its quality and safety, featuring the Prestige® line of vaccines with updated influenza strains. Veterinarians and horse owners trust the Merck Animal Health pharmaceutical line, headlined by Panacur® (fenbendazole), Banamine® (flunixin meglumine), Regu-Mate® (altrenogest) and Protazil® (1.56% diclazuril) antiprotozoal pellets.

Partnering with you to create new standards of care and improved infectious respiratory disease is a key focus for the future. The recent introduction of the industry’s most current equine influenza protection is a testament to this collaboration through the ongoing Merck Animal Health Equine Respiratory Biosurveillance Program.

A Storied History of Giving Back Dedicated to offering even more than a portfolio of exceptional products, Merck Animal Health invests in our industry, profession and community. • Merck Animal Health Veterinary Wellbeing Study, shining a light on one of the industry’s most pressing issues of mental distress and suicide • More than $800,000 in student scholarships granted annually • More than 32,000 doses of life-saving vaccines donated to horses in rescue through the UHVRC, an 11-year partnership with AAEP • Vet Story Night raised $22,000 for the AAEP Foundation in 2018, and the third annual event will take place Sunday, Dec. 8, 2019, during the AAEP Convention • $1.5 million in donations to natural disaster relief in 2017

Discover how Merck Animal Health is working for you. Contact a Merck Animal Health sales representative or visit merck-animal-health-equine.com. INDUSTRY AAEP News October 2019 IX

Delegate Corner: Veterinary leaders advocate for key issues on Capitol Hill By Stuart Brown II, DVM

The AVMA House on behalf of the AVMA membership. A revised policy of Delegates resolution affecting veterinary dentistry and presented summer meeting with language incorporated as supplied by the AAEP convened Aug. 1-2 though our 2019 position statement was referred back to in Washington, the AVMA Executive Board for further consideration D.C., in conjunction with the AVMA Annual Convention. before adoption by the HoD. Support was also expressed Dr. Rebecca Stinson and I represented AAEP as your for the passage of resolutions affecting the judicious use of alternate delegate and delegate, respectively. therapeutic antimicrobials in private practice, a revised policy on pet insurance, sexual harassment awareness in On Aug. 1, the Government Relations Division (GRD) of the veterinary profession, and revisions to the Model the AVMA organized the largest single-day advocacy effort Veterinary Practice Act. Bylaws amendments considered ever by the veterinary profession as HoD members visited during the session addressed qualifications for service on with congressional leaders from their respective states to the AVMA board of directors and advancing the role of discuss three key topics: The Fairness to Pet Owners Act, the Council on Research. Veterinary Loan Repayment Enhancement Act and the Association Health Plans Act. Regretfully, this session marked the conclusion of service by my colleague Dr. Rebecca Stinson in her role as the Dr. Stinson and I were asked to meet with key congressio- AAEP alternate delegate. Dr. Stinson has accepted a nal offices concerning issues facing the equine industry, position with the AVMA Trust focusing on service to particularly horse racing. These productive visits served as veterinary student constituents. We join all those from the an opportunity to answer questions about our industry’s AVMA who at the conclusion of this session recognized challenges and the roles veterinarians play daily as equine her service and dedication to the profession and the AAEP professionals in the care of the equine athlete. In addition, in this vital role on behalf of our membership. We wish many expressed their appreciation and pleasure in the her the best in her new endeavors. recent passage of the PAST Act. Dr. Ted Yoho (R-FL), a Dr. Margo Macpherson will fill the remainder of longtime friend of the AAEP who introduced the legisla- Dr. Stinson’s term. Please contact us if you have questions tion with fellow veterinarian Rep. Kurt Schrader (D-OR), or concerns we might address. You can reach us at delivered the opening address at the HoD meeting. He [email protected] and [email protected]. emphasized the importance of our political engagement and advocacy with constituent legislative leaders to shape policy that impacts all aspects of veterinary medicine. Dr. Brown serves as AAEP’s delegate to the AVMA House of Delegates. He is a partner in Hagyard Equine Medical Our regular HoD session convened the following day with Institute in Lexington, Ky., and a member of the AAEP’s various resolutions and bylaws amendments to consider Racing Committee.

MEMBERSHIP

Benefit: Save money with The Veterinary Club

Fortify your bottom line through significant savings on Cook, longtime practice manager at B.W. Furlong & many of the products and services used in everyday Associates in Oldwick, N.J. “We’ve saved thousands. In practice as a member of The Veterinary Club group fact, the savings would pay for a certified vet tech’s purchasing program, a complimentary benefit of your salary.” AAEP membership. The 625 AAEP members enrolled in The Veterinary Club Obtain substantial pre-negotiated discounts on a robust collectively spend approximately $2 million through the catalog of more than 400 contracted suppliers, including service each year. Many accrue annual savings that exceed cell phone plans, courier services, office supplies, the cost of their AAEP membership. diagnostic imaging equipment, credit card processing and much more. In addition to the online catalog, members of Start saving today by registering at theveterinaryclub. The Veterinary Club receive a 7% in-store discount at the com. If you have questions about this benefit, contact Apple Store on purchases of most Apple products. Megan Gray, member concierge, at [email protected] or (859) 233-0147. “We key on about 10 contracts, with Staples, Verizon and PC Connection being the most valuable,” said Nadia X AAEP News October 2019 MEMBERSHIP

Veterinarian makes the case on behalf of abused horses in West Virginia

A year after receiving her “Most prosecutors are familiar with veterinary degree human issues but more than likely from Mississippi have never prosecuted an equine State University in case,” said Dr. Mason. “Make an 1992, Dr. Clara appointment to sit with the Mason opened her prosecutor and show them the ambulatory difference between an abused horse veterinary practice and a healthy horse, what is allowable in Winfield, W. Va., and not allowable, humane and not and soon became humane. Typically, that will resolve entwined in an equine cruelty case most of the issues the prosecutor may that would commence a quarter-cen- have with the case.” tury commitment to abused and at-risk horses in the state. Equine cruelty cases often get delayed for up to a year before going The outcome, in which one horse was to trial so Dr. Mason takes as many euthanized and two others rescued photographs on-site as possible to and rehomed, and the ensuing court not only help make the case in court case inspired the August honoree of but to assist with information recall. the AAEP’s Good Works for Horses Photos document all food and water Campaign to work with state legisla- sources—or lack thereof—as well as tors to enact more stringent animal the body condition of each horse cruelty laws. Despite fortified laws, with its name, date, time, tempera- however, enforcement remained prob- ture and estimated weight written on lematic due to limited resources an erasable board that appears in Dr. Mason conducts a follow-up exami- among police departments and each photo. nation on a horse involved in a recent humane societies as well as a general seizure case. ignorance of what horse abuse looks “Dr. Mason has been instrumental in like. aiding numerous county officials in equine abuse at the AAEP’s annual equine neglect and cruelty cases for convention; and, while a member of Dr. Mason began educating sheriff’s many years,” said her Good Works the AAEP’s Welfare and Public Policy departments in her region and serving nominator Tinia Creamer, founder Advisory Council, she was part of a as a guest speaker for several equine and executive director of Heart of team that in 2018 created comprehen- rescue organizations that host educa- Phoenix Rescue. “Her expertise has sive online resources to help AAEP tional events for law enforcement. Dr. proven vital time and again to members work with clients and law Mason typically speaks on the topics gaining justice for horses across enforcement to prevent equine abuse of dentistry, body condition and West Virginia.” and neglect. Those resources are premises warning signs that should accessible at aaep.org/owner- trigger further investigation. Attendees Dr. Mason willingly shares her guidelines/equine-welfare. Dr. Mason are provided gift bags that contain experience and knowledge with also serves as the AAEP’s representa- weight tapes, thermometers, body fellow practitioners. She has presented tive to the AVMA’s Animal Welfare condition score charts and other tools on the topic of prosecuting cases of Committee. to help with equine cruelty cases.

Dr. Mason assists on-site with cruelty investigations once or twice per month, and typically appears in court Throughout 2019, the AAEP’s Good Works for Horses Campaign will once per month to aid with prosecu- spotlight AAEP-member practitioners whose volunteer efforts are tion of such cases. She encourages improving the health and welfare of horses. To discover the Good Works colleagues involved with equine of AAEP veterinarians or nominate a Good Works candidate, visit aaep. cruelty cases to meet in advance with org/horse-owners/good-works-horses. For more information on nominating the prosecutor to answer questions a veterinarian for this program, contact Giulia Garcia at [email protected]. and help guide them through the case. FOUNDation AAEP News October 2019 XI

AAEP Foundation supporting pertinent studies by up-and-coming researchers

In support of exceptional science being conducted by promising young researchers, the Foundation is providing $99,051 for five equine research projects being investigated by AAEP-member graduate students and residents.

“These projects offer exciting possibilities for the health and welfare of horses,” said Dr. Anthony Blikslager, chairman of the AAEP Foundation Advisory Council Research Subcommittee. “Collectively, they have the potential to yield new treatments for problematic conditions, expand access to novel therapies, increase racehorse safety and enable breeders to raise healthier horses.”

The supported projects with recipient photos and brief descriptions of research goals, are:

Investigating equine endometrial signaling pathways using an organoid culture system Dr. Riley Thompson, Smithsonian Institution Developing equine endometrial organoids will allow researchers to evaluate new treatment options for uterine diseases, reduce the use of live animals for research, lead to significant economic savings and Equine platelet-derived peptides as novel improve animal welfare. disease-modifying osteoarthritis drugs Dr. Jessica Gilbertie, North Carolina State University Validation of an Finding the key components of a specialized formulation antemortem of PRP that are anti-inflammatory and increase high- diagnostic test for quality hyaluronic acid production will lead to an off-the- equine neuroaxonal shelf osteoarthritis therapy that eliminates the variability dystrophy (eNAD) of traditional PRP. Dr. Callum Donnelly, University of Identification and validation of California-Davis alleles responsible for cardiac Examining genetic arrhythmias and atrial variants (mutations) fibrillation involved with the Dr. Sian Durward-Akhurst, enzymes responsible for University of Minnesota vitamin E metabolism Developing genetic tests for cardiac will influence the arrhythmias, particularly atrial development of tests to fibrillation, will allow for increased aid in the diagnosis of horses with eNAD and provide monitoring of genetically at-risk tools for genetic screening in order to prevent future horses, retirement from racing cases. before the onset of potentially fatal arrythmias and decreased incidence of arrythmias in breeding animals. If you would like to support the Foundation’s equine research efforts, please make a gift online at Understanding the role of MHCI compatibility in aaepfoundation.org. equine allogenic mesenchymal stem cells Dr. Aileen Rowland, Texas A&M University Understanding the effect of differing major histocompatibility complex haplotypes is critical in identifying an acceptable allogeneic MSC donor. Identification of a universal allogeneic MSC would make stem cell therapy more obtainable via federal approval, client expense and ease of use. XII AAEP News October 2019 FOUNDation

AAEP Foundation grants top $700,000 for second consecutive year

The Foundation Advisory Council at its summer meeting approved $731,000 in grants for 28 programs and projects that benefit the welfare of horses. Technologies The disbursement includes support for 10 working equid welfare projects administered by “Equitarian” veterinarians throughout Central and South America, the Caribbean Veterinary and the United States, along with funding for 55 scholarships to help students and recent graduates offset the Pulse

financial strain of veterinary school. Gage,

Allocated funds are also earmarked for four disaster pre- Trudy paredness programs, including a large animal rescue course hosted by the Lincoln Memorial University CVM and disaster preparedness training offered by the Los Angeles County Animal Care Foundation. The AAEP Foundation is supporting 10 working equid Other projects receiving funds include essential skills welfare projects and programs in 2019-2020. workshops and convention programming for students as well as five equine research projects spearheaded by For more information about the Foundation and its graduate students and/or residents (see article on page XI). impact on horse welfare, visit aaepfoundation.org.

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Highlights of recent clinically relevant papers

Osteochondral fragmentation of the carpus these fibres. Cemental caries progressed to affect enamel, dentine and pulp. This retrospective study by Robyn Graham and colleagues in Equine peripheral caries cause different patterns of the UK, China and the USA aimed to identify associations cemental lesions which may be dependent on the route of between the severity and location of osteochondral bacterial invasion. Gross examination can underestimate the fragments in the carpus and to describe the racing true extent of peripheral caries. performance of horses pre- and post-arthroscopic removal in Thoroughbreds and Quarter Horses. The medical and racing records of racehorses that Risk of incisional infection after celiotomy underwent carpal arthroscopy between 2006 and 2016 due In this prospective study Isabelle Kilcoyne and colleagues in to clinical signs and radiographic findings consistent with the USA assessed incidence of incisional infection in horses carpal chip fragmentation were retrospectively reviewed. following management with one of three protective dressings Signalment, location of fragmentation and grade of defect after exploratory celiotomy to treat acute signs of abdominal after arthroscopic removal and debridement were described pain (colic) and determined the risk of complications and logistic regression used to identify factors associated with associated with each wound management approach. an unsuccessful return to racing. The 85 horses in this study were assigned to three In total, 828 horses (416 Quarter Horses and 412 post-operative treatment groups. The incision sites were Thoroughbreds) underwent 880 carpal arthroscopies for covered with either a sterile cotton towel (group 1) or a removal of fragments. A total of 65% and 27% of lesions were polyhexamethylene biguanide-impregnated dressing (group bilateral in Quarter Horses and Thoroughbreds, respectively, 2), both of which were secured with four or five cruciate with the most commonly affected bone in both breeds being sutures of nonabsorbable monofilament. Group 3 had sterile the dorsodistal radial carpal bone. Overall, 82% of horses gauze placed over the site, secured with an iodine- raced post-surgery, with 69.5% racing at the same or a higher impregnated adhesive drape. Demographic and level. Factors associated with horses not returning to racing clinicopathological data, intraoperative and post-operative post-surgery were increasing horse age, being female, and a variables, and development of complications were recorded lesion grade of 4/4, while racing pre-surgery appeared and compared among groups. Follow-up information was protective. collected 30 and 90 days after surgery. Incidence and odds of There were significant differences between the location incisional complications were calculated. and severity of lesions in Quarter Horses compared to The study was completed by 75 horses. Group 3 typically Thoroughbreds. The majority of horses returned to racing had dressing displacement necessitating removal during following surgery, with lesion severity affecting performance. anaesthetic recovery; dressings were in place for a mean of 44 and 31 h for groups 1 and 2, respectively. Purulent or Peripheral caries persistent serosanguinous incisional discharge (infection) was detected in 11 of 75 (15%) horses (2/24, 0/26, and 9/25 from This study by Dewi Borkent and colleagues in the UK groups 1, 2, and 3, respectively). Odds of incisional examined cheek teeth affected by periperhal caries (PC) complications were significantly greater for group 3 than for histologically and ultrastructurally in order to establish the groups 1 or 2. route of cariogenic bacterial invasion and to describe the These results suggest that risk of infection after celiotomy resulting pathological changes. for treatment of colic is lower for incisions covered with A total of 16 cheek teeth from horses that had died of sterile towels or polyhexamethylene biguanide-impregnated non-dental related disease with varying grades of PC were dressings secured with sutures than for incisions covered examined alongside four control teeth (no PC). The teeth with gauze secured with iodine-impregnated adhesive were macroscopically assessed. Of those with PC, 11 had drapes. partial cemental caries (grade 1.1 PC), three had total cemental caries (grade 1.2 PC), three had caries of cementum and the underlying enamel (grade 2 PC) and two Effects of magnesium on headshaking had caries of cementum, enamel and dentine (grade 3 PC). Samples for histological and electron microscopy In this study Shara Sheldon and colleagues in the USA examination were prepared. evaluated the effects of oral magnesium alone or in Bacteria from plaque entered the peripheral cementum combination with boron on headshaking behaviour in perpendicular to the sides of the teeth alongside Sharpey’s fibres affected horses. or vascular channels or more horizontally alongside exposed This dietary trial took place over 42 days in 12 horses intrinsic fibres and cemental growth lines. Intra-cemental (6 horses diagnosed with trigeminal-mediated headshaking bacterial spread caused varying patterns of cemental caries as and 6 unaffected healthy controls). All horses received a identified histologically: horizontal flake-like lesions (type A), hay diet and were randomised into three treatment vertical flake-like lesions (type B), flask- like lesions (type C) and groups: pelleted feed combination (PF), pelleted feed small ellipsoid, lytic lesions (type D). Regardless of mechanism, combination with magnesium (M), and pelleted feed cariogenic bacteria commonly tracked along the intrinsic fibres combination with magnesium-boron (MB) with a week in lines of arrested growth (LAGs), causing further washout of hay only between treatments. Headshaking demineralisation of adjacent cementum and disintegration of behaviour and biochemical blood variables were assessed

at baseline (hay only) and then after each week of basal insulin concentrations were associated with more severe supplementation. lameness. All three diets increased blood ionised and total 2+ magnesium. Groups M and MB further increased Mg when Post-partum uterine lavage compared to PF. Horses receiving treatments had a significant reduction in headshaking behaviour, as measured In this retrospective study Anna Mitchell and colleagues in by incidence rate ratio (IRR), when compared to the USA, UK and Australia investigated the effect of routine unsupplemented hay diet (44% for PF, IRR, 0.558; 52% for M, post- partum uterine lavage on endometrial cytology, culture, IRR, 0.476; and 64% for MB, IRR, 0.358). and pregnancy rates in Thoroughbred broodmares. Magnesium in combination with boron had the greatest The 32 Thoroughbred mares in this study were housed on decrease in headshaking. Oral supplementation with a single farm in Australia in 2014 and 2015. In the control year magnesium or magnesium in combination with boron should (2014), post-partum uterine lavage was not performed. In the be considered in horses affected with headshaking. treatment year (2015), all mares received a uterine lavage 3 days post-partum. In both years, endometrial swabs were obtained for culture and cytology at the first post-partum Clodronic acid treatment for navicular syndrome oestrus (foal heat swab) and the second post-partum oestrus (second heat swab), prior to the mare being bred by natural In this field study David Arguelles€ and colleagues in Spain cover at the second post-partum oestrus. There was no assessed the clinical efficacy of clodronic acid in horses significant difference in bacterial culture rates from foal heat diagnosed with navicular syndrome. or second heat swabs between the control and treatment The 11 horses in this study all had clinical and years. Assessment of endometrial cytology of the foal heat radiographic findings compatible with navicular syndrome. swab and second heat swab revealed a significantly higher Magnetic resonance imaging was performed in 5 of the 11 proportion of polymorphonuclear cells (PMNs) in the control horses. The animals were treated with an intramuscular dose year compared with the treatment year. Positive culture of clodronic acid of 765 mg/horse, administered over three and cytology rates were significantly higher at foal heat than separate injection sites. Horses were subjected to lameness at the second post-partum heat in both years. No association and accelerometric evaluations before and at 7, 30 and of year, cytology, or culture with pregnancy rates was 90 days after treatment. Clinical improvement was observed identified. in 6 of the 11 horses, showing a mean reduction of two These results indicate that routine post-partum uterine degrees in lameness score. Accelerometry in these horses lavage significantly reduces the presence of endometrial revealed increased velocity, stride length, stride regularity PMNs at first and second post-partum oestrus but does not and dorsoventral displacement of the centre of gravity reduce endometrial culture rates or increase pregnancy together with a reduction in stride frequency, suggesting a rates. gait improvement. S. WRIGHT These results demonstrate that intramuscular clodronic EVE Editorial Office acid can be useful for lameness reduction in some horses with navicular syndrome. References Arguelles,€ D., Saitua, A., de Medina, A.S., Munoz,~ J.A. and Munoz,~ A. Characteristics of endocrinopathic laminitis (2019) Clinical efficacy of clodronic acid in horses diagnosed with navicular syndrome: A field study using objective and subjective The aim of this study by Melody de Laat and colleagues in lameness evaluation. Res. Vet. Sci. 125, 298-304. Australia and Germany was to improve the risk assessment Borkent, D., Smith, S. and Dixon, P.M. (2019) A histological and capabilities of clinicians, and to inform management ultrastructural study of equine peripheral caries. Equine Vet. J. Epub ahead of print; https://doi.org/10.1111/evj.13134 strategies, for acute endocrinopathic laminitis by prospectively examining the phenotypic, hormonal, and Graham, R.J.T.Y., Rosanowski, S.M. and McIlwraith, C.W. (2019) A 10-year study of arthroscopic surgery in racing Thoroughbreds and clinical characteristics of the disease in a large cohort. Quarterhorses with osteochondral fragmentation of the carpus. The 301 cases in this study were privately owned horses and Equine Vet. J. Epub ahead of print; https://doi.org/10.1111/evj. ponies diagnosed with laminitis or a history of laminitis. 13145 Following informed consent from the animal’s owner, Kilcoyne, I., Dechant, J.E., Kass, P.H. and Nieto, J.E. (2019) Evaluation veterinarians provided information on each case via an online of the risk of incisional infection in horses following application of questionnaire. Serum insulin and plasma adrenocorticotrophic protective dressings after exploratory celiotomy for treatment of colic. J. Am. Vet. Med. Assoc. 254, 1441-1447. hormone concentrations were measured in each case. Most cases were recruited in spring (109/301). Concurrent de Laat, M.A., Sillence, M.N. and Reiche, D.B. (2019) Phenotypic, hormonal, and clinical characteristics of equine endocrinopathic equine metabolic syndrome and pituitary pars intermedia laminitis. J. Vet. Intern. Med. 33, 1456-1463. dysfunction resulted in higher basal insulin concentrations Mitchell, A.R.M., Scott, C.J., Cheong, S.H., Carrigan, P., Diel de than if an animal had a single underlying cause for their Amorima, M. and Collins, C.D. (2019) The effect of routine laminitis. The insulin concentration was negatively correlated postpartum uterine lavage on endometrial cytology, culture, and with the animal’s height, being higher in ponies than horses pregnancy rates in Thoroughbred broodmares. J. Equine. Vet. Sci. and was positively correlated with their grade (severity) of 80, 5-9. laminitis. Sheldon, S.A., Aleman, M., Costa, L.R.R., Weich, K., Howey, Q. and Madigan, J.E. (2019) Effects of magnesium with or without boron These results indicate that horses and ponies with concurrent on headshaking behavior in horses with trigeminal-mediated endocrinopathies have more marked hyperinsulinaemia. Higher headshaking. J. Vet. Intern. Med. 33, 1464-1472.

Editorial Professional wellness of the veterinary team

Personal and professional wellness of veterinarians and mental health is about the whole veterinary team and so the veterinary staff are receiving increased attention in veterinary focus needs to be how all members of the practice can stay publications and conferences, social media and the non- mentally and physically healthy. veterinary press. Recent suicides of high-profile, socially Are these problems only present in the veterinary world? harassed or victimised veterinarians have caused And if not, can we learn and collaborate with other consternation within the profession. There is an increased professions? Research shows that human physicians also recognition that stress and compassion fatigue, coupled with suffer from higher levels of mental health issues than one a demanding workplace environment, are adversely might expect (Thomas et al. 2018). affecting the mental well-being and physical health of Military veterans and police officers are known to suffer veterinarians. from mental health issues associated with their profession Several studies have estimated that the incidence of (Van Houtert et al. 2018). An app (Backup Buddy) was suicide in the veterinary profession in countries such as United developed to help and support front-line police officers in States, UK, Australia and Norway is double that of the other numerous UK police forces to identify the most commonly healthcare professionals and four times that of the general reported conditions and to provide them with advice and population (Bartram and Baldwin 2008; Stoewen 2015). A support as to what users could use to help themselves or number of influencing factors have been postulated as colleagues. The significant benefit of an app is that it is with contributing to this increased risk: personality factors, someone whenever they have their smartphone (and does undergraduate training, professional isolation, work-related not depend on having Internet access via mobile data or Wi- stressors, attitudes to death and euthanasia, access and Fi). On the basis of the success of Backup Buddy, it was technical knowledge, psychiatric conditions, stigma around decided to develop an app specially to provide for the mental illness, and suicide contagion (Bartram and Baldwin needs of the veterinary market and so the ‘Vets in Mind’ app 2008). was designed. The goal of this app is to reduce the stigma Also a heavy workload, insufficient rest and prolonged, surrounding mental health through case stories and intense contact with animals and their owners can result in information. The aim is to give the whole veterinary team the occupational stresses and burnout. Veterinarians who neglect tools to become cognisant of the range of mental health their physical, emotional and psychological needs can find issues by providing short general information on a number of themselves suffering from ‘compassion fatigue’ and it has mental health topics (such as anger, anxiety, substance been estimated that between 15 and 67% of veterinarians abuse, depression, burn out, self-harm and suicide), as well as are at high risk of burnout (Brannick et al. 2015). what measures one can take for oneself, or to help a However, the research done comes mainly for the colleague, friend or family member to help signpost them to developed world. And even there, scientific evidence on appropriate professional support and providing helpline topics like compassion fatigue is lacking. contact numbers in many countries. It also provides The good news is that a lot of professional wellness information on how one can build up one’s own resilience initiatives are being set up. In September 2018, the WSAVA and well-being to reduce the chances of suffering from such Professional Wellness Group was formed. One of its first conditions. The app very importantly does not register user actions was to develop a survey in seven different languages details so that privacy is ensured and has both articles and regarding professional wellness. This survey contained the links to information provided via many initiatives that are Kessler Psychological Distress Scale, which determines being instigated across the world, and also has videos with the presence or absence of severe psychological distress, the members of the veterinary market talking about their own satisfaction with life scale (Diener et al. 1985) and an experiences. adjusted version of the satisfaction with career scale. In total, The app is being provided by a not-for-profit consortium 4306 respondents filled in the survey. The results will be of interested parties who currently include Partners who are published later this year. funding the project to date; primarily the Petplan Charitable The main results were that professional wellness is an issue Trust and also the North American Veterinary Community, around the globe. In different continents, the contributing Circa Healthcare and Vetstream; as well as Members who factors and levels of awareness of mental health issues differ. are providing content and marketing services: The British In the United States, the prevalence of mental ill health is well Equine Veterinary Association, American Association of recognised, with student debt and financial issues seen as Equine Practitioners, Veterinary Support North Ireland and significant contributors, whilst in Asia and Africa, awareness Scotland, VetTechLife, Not One More Vet and the Riptide regarding mental health issues is low and speaking about project. these topics does not seem to be done as openly as in other The app does not pretend to be a single solution; instead, countries. it aims to complement and be a useful tool to sit alongside It seems that younger vets have more mental health many other initiatives and existing programmes already in issues than mature vets and females appear to find a good place run by various associations, organisations, charities and work-life balance to be a significantly difficult issue. And it is support groups around the world for all members of the not only about veterinarians: veterinary nurses are also veterinary market whether they are in practice, academia or reporting mental health issues. It is important to realise that companies and charities in the veterinary market.

Continued on page 550 © 2019 The Authors. Equine Veterinary Education published by John Wiley & Sons Ltd on behalf of EVJ Ltd This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. North America Fall Brochure now available Fall 2019 download to www.vetpd.com at USA: 18-19 Oct Donkey Medicine & Surgery Lone Star College, near Houston, TX 26-27 Oct Ultrasound of the Mid-Distal Limb & Stifle for Equine Practitioners Stillwater Equine Veterinary Clinic, Minneapolis, MN 26-27 Oct Ultrasound of the Equine Upper Limb, Neck, Back & Pelvis Mid-Atlantic Equine Medical Center, Princeton, NJ 4-5 Nov Ultrasound-Guided Orthopedic Injection Techniques & Therapies Janssen Veterinary Clinic, near Indianapolis, IN 15-16 Nov Evidence-Based Podiatry for Equine Practitioners Tennessee Equine Hospital, near Nashville, TN 22-23 Nov Rehabilitation for Lower Limb Tendon & Ligament Conditions Equine Performance Center, Ocala, FL Canada: 8-9 Nov Hindlimb Lameness Diagnostics (incl. Objective Gait Analysis) & Therapies Moore Equine Veterinary Centre, Calgary, Canada

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Case Report Rostral mandibulectomy for treatment of a sarcoma in a 16-year-old Thoroughbred mare M. Kohler€ †* , M. Koene†, E.-C. Schliewert†, H. Aupperle‡ and H.-R. Krause§ †Tierklinik Lusche€ GmbH, Bakum; ‡Labor Laboklin, Bad Kissingen; and §Klinikum Bremen-Mitte Gesichts-und Kieferchirurgie, Bremen, Germany *Corresponding author email: [email protected]

Keywords: horse; sarcoma; surgery; mandibulectomy

Summary Clinical findings A 16-year-old Thoroughbred mare presented with a 1-year The mare was bright, alert, responsive and markedly history of a growing mass on the rostral mandible. Biopsy underweight with a body condition score of 3/9 (Henneke performed by the referring veterinarian revealed chronic et al. 1983). A mass of approximately 15 cm in diameter was fi granulating brosis and stomatitis. Due to progressive loss of observed on the rostral part of the mandible (Fig 1). Using the body condition and increasing size, the mare presented to Triadan dental nomenclature, the incisors of the lower the clinic. Radiographic examination of the mandible arcade 301–303 and 401–403 were dislocated but not loose. revealed osteolytic lesions. Mandibulectomy was performed The incisors of the lower arcade were unremarkable in shape ’ under general anaesthesia. The horse s demeanour and feed and length on inspection but occlusion with the incisors of fi intake improved signi cantly and the cosmetic outcome was the upper arcade was not present (Fig 1a). Moderate fi acceptable. Histopathological examination con rmed a seromucous discharge from the left nostril, an inspiratory fi sarcoma, most likely a brosarcoma. upper airway noise, slightly enlarged mandibular lymph nodes, and a systolic murmur (grade 2–3/6) were noted. Introduction Palpation of the mass was not tolerated and a malodorous smell was obvious. Examination under sedation revealed Compared to other species, like dogs or cats, tumours in severe stomatitis with deposition of feed material. horses are relatively uncommon. However, tumours of the mandibular and pharyngeal region are frequently observed (Dorn and Priester 1976). In previous reports, lymphoma Radiographic examination (Greet et al. 2011), ameloblastoma (Kutzler et al. 2007; Radiographic examination of the mandible revealed Mendez-Angulo et al. 2014), carcinoma (Monteiro et al. osteolysis of the rostral mandible (Figs 2 and 3). On fi fi 2009), broma (Richardson et al. 1991), brosarcoma (Barber ventrodorsal projections, severe osteolytic changes of the et al. 1983; Carmalt and Linn 2013) and osteosarcoma (Bush entire rostral mandible were noted (Fig 3). Radiographic et al. 2007) of the maxilla or mandible have been described. images of the lungs were unremarkable. No age, sex or breed predilection has been shown (Bush et al. 2007; Monteiro et al. 2009). Due to economic reasons and poor prognosis, treatment is frequently not attempted Diagnosis and treatment and the horse is subjected to euthanasia (Bush et al. 2007; Interpretation of clinical and radiographic findings suggested Monteiro et al. 2009). This case report describes successful neoplasia with sarcoma, fibroma, ameloblastoma or conventional rostral mandibulectomy in a 16-year-old osteosarcoma being the most common tumours in this area. Thoroughbred mare. Previous veterinarians had recommended euthanasia. Benign and malignant tumours originating from epithelial cells, Case history connective tissue and bone have been described in horses but reports of treatment are sparse. A human oral surgeon A 16-year-old Thoroughbred mare was presented to the with extensive experience with expansive oral tumours was Tierklinik Lusche€ with a 12-month history of a hard mass in consulted and conventional rostral mandibulectomy was the rostral aspect of the mandible. The referring veterinarian attempted. The extent of additional reconstruction necessary had submitted a tissue sample for histopathological to stabilise the mandible was to be made intraoperatively. examination that revealed purulent to granulomatous inflammation and chronic granulating fibrosis and stomatitis Surgery with plant particles. No signs of malignancy were noted but interpretation was limited due to autolysis. The mass was The mare was fasted for 12 h prior to surgery. A catheter was reported to have slowly increased in size over the previous placed aseptically into the left jugular vein and flunixin 12 months; feed intake was initially described as normal. meglumine1 (1.1 mg/kg bwt i.v.), gentamicin2 (6.6 mg/kg bwt Over time, the mare developed exuberant granulation i.v.) and procaine penicillin3 (15,000 iu/kg bwt i.m.) were tissue with anorexia, halitosis and ulceration of the mass. administered prior to induction of anaesthesia. The horse was Due to the progressive weight loss, the lesion was sedated with xylazine4 (1 mg/kg bwt i.v.) and anaesthesia considered to be painful. was induced with ketamine1 (2 mg/kg bwt i.v.) and

a) b)

Fig 1: Clinical picture of a tumour of the horse’s mandible. Inspection was possible after sedation of the horse. The incisors were dislocated but not loose (a). The entire gingival mucosa showed signs of inﬂammation and irritation with packing of food (b).

Fig 2: Lateral view of the mandible of a 16-year-old mare with progressive swelling of the mandible. There is notable loss of detail and lysis of the mandibular bone. Fig 3: Dorsoventral projection of the mandible. The lysis of the mandibular bone is obvious. All teeth are present but displaced. diazepam2 (0.2 mg/kg bwt i.v.). The mare was intubated The mandibular symphysis seems to be unimpaired. orotracheally and anaesthesia was maintained with fl inhalation of iso urane. The mare was positioned in dorsal Post-operative care recumbency. A speculum was used to allow access to the oral cavity. Intraorally, an incision perpendicular to the Following recovery, the mare was allowed access to water. mandible was made into the soft tissue from the diastema to Soaked hay and soaked concentrate were reintroduced the approximately 1 cm rostral of the mental foramen. The day after surgery. Procaine penicillin3 (15,000 iu/kg bwt i.m. q. surgical field was consistent with radiographic changes noted 24 h), gentamicin2 (6,6 mg/kg bwt i.v. q. 24 h), flunixin in the dorsoventral projection, in which the bone revealed meglumine1 (1.1 mg/kg bwt i.v. q. 12 h) and omeprazole8 minor alterations but the mandibular symphysis seemed (4 mg/kg bwt per os q. 24 h) was administered for 5 days. normal. Ideally, the resection should have involved more The oral cavity was rinsed twice daily with a physiological caudal parts of the mandible but resection of these sections saline solution containing 2% iodine9. Sutures were removed would have resulted in instability of the jaw. The tissue was 7 days post surgery under sedation. Only a few sutures were elevated from the bone, the radiographically altered still in place, but the tissue covering the mandibular bone segments of the rostral mandible were resected using a bone was completely granulated at that time (Fig 6). saw and the bony edges were smoothed with a shaver 5 (Arthrex )(Figs 4 and 5). Haemostasis was achieved with Pathology report electrocautery6. Upon examination, the remaining bone and surrounding soft tissue appeared macroscopically normal. The The tissue sample was 13.0 9 6.0 9 7.0 cm in size. The cut tissue was closed with interrupted horizontal mattress sutures surface showed multiple firm white nodules (Figs 7 and 8). in two layers using polyglycolic acid material7. After the demineralisation process (Osteomollâ10), the A dental floating was performed to remove sharp points tissue was cut longitudinally. Bone structures were not and prevent limitation of mastication as well as premature recognisable. Representative sites were embedded in manipulation of the surgery site. paraplast and stained with haematoxylin-eosin (HE).

a) b)

Fig 4: Intraoperative view of the varied structure of the mandible after removing food. The inﬂammation of the gingiva and the dislocated incisors are visible (a). The tissue has solid texture and the teeth are ﬁxed (b).

a) b)

c) d)

Fig 5: Surgical intervention (mandibulectomy) of the tumour and area around the modiﬁed region of the mandible. First, the mucosa was resected from the mandibular bone (a). The inﬁltrated one was then resected in macroscopically normal region and the edges were smoothed (b and c). A two-layer wound closure was performed (d).

Microscopically, a compact growth of spindle-shaped to ﬁgures/HPF were counted (Fig 9). Only small amounts of pleomorphic cells was found. Hypochromatic oval nuclei with collagenous matrix were produced. Additionally, extensive severe anisocytosis and anisokaryosis were surrounded by areas of necrosis and purulent inﬂammation as well as plant moderate amounts of pale cytoplasm. Up to four mitotic pieces were present.

a) b)

Fig 6: Surgery site 7 days’ post-operatively. Some of the sutures are loose and feed material was rinsed off twice daily (b). At rest, the tongue of the mare hung out rostrally of the oral cavity (a).

Fig 8: Longitudinal cut with multiple ﬁrm white nodular masses which resulted in destruction of the mandibular bone structures.

Fig 7: Submitted tissue from the mandible containing four The tongue intermittently protruded 3–5 cm from the rostral displaced incisors. Large ulcerated areas (brown) were noted in oral cavity (Fig 10a). No abnormal respiratory noises were the mucosa. appreciated. The wound was completely granulated, no feed material was adherent (Fig 10b). The bony margins were Neoplastic cells infiltrated the bone leading to severe not reactive on radiographic examination (Figs 11 and 12). destruction of organ-specific structures. Further recheck examinations were performed by the In summary, a highly malignant sarcoma was diagnosed referring veterinarian and were reportedly unremarkable. and fibrosarcoma appeared most likely. Spindle cell During a follow-up interview with the owners over the osteosarcoma seemed less likely as the neoplasm appeared telephone 6 months post surgery, the owners reported good to extend from the periphery into the bone. appetite and significant weight gain. The mare was reported to have an inspiratory noise and intermittent nasal discharge Follow-up of serous to haemorrhagic character from the right nostril. The mandibular lymph nodes were described as enlarged but not The mare presented for follow-up examination 4 weeks post painful. The owners declined further evaluation. surgery. The owners reported that the mare was bright with a good appetite. On physical examination, the mare was Discussion bright, alert and responsive with mild seromucous discharge from the right nostril. The right mandibular lymph node was Oral tumours are generally rare in horses but tumours of the slightly enlarged but not painful. Malodour was not noted. head are commonly described (Barber et al. 1983; Orsini

Fig 11: Laterolateral radiograph of the mandible 4 weeks after rostral mandibulectomy. Fig 9: The spindle-shaped to pleomorphic tumour cell population is characterised by hypochromatic oval nuclei and moderate amounts of pale eosinophilic cytoplasm. Multiple mitoses (arrow) Once the size and type of the tumour have been and small amounts of collagen were present. identified, therapeutic options can be evaluated. Successful excision of oral tumours has been described in et al. 1991; Richardson et al. 1991; Bush et al. 2007; Veraa other species (Verstraete 2005), while successful reports of et al. 2009; Lechartier et al. 2015). Clinical symptoms of therapeutic approaches in equine medicine are rare. Rostral tumours of the head are generally related to the location of mandibulectomy on five horses with mandibular tumours, the tumour. With oral tumours, grossly abnormal tissue masses, three of these with ossifying fibromas, was reported with oral bleeding, dysphagia, weight loss, recurrent fever, cosmetically acceptable results. It is recommended to depression and halitosis are common clinical signs. Further conserve the symphysis of the mandible to maintain stability diagnostic options include different cross-sectional imaging of the mandible during mastication (Richardson et al. 1991). modalities to verify the extent of the tumour and biopsy Surgical excision of the affected tissue can be difficult due to (Barakzai 2010; Knottenbelt and Kelly 2010), which can limited access through the oral cavity (Snyder et al. 2008). establish a concise definitive diagnosis. However, biopsy may Mandibulectomy as treatment of an undifferentiated be difficult due to location of the tumours. Fine needle sarcoma (Carmalt and Linn 2013), ameloblastoma (Mendez- aspirates are easier to perform but if only a limited number of Angulo et al. 2014), odontoma (Snyder et al. 2008) and cells or just marginal inflammatory tissue are obtained, they ossifying fibroma (Morse et al. 1988; Richardson et al. 1991) in are not always diagnostic (Knottenbelt and Kelly 2010). horses has been described. Resection of premaxillary and

a) b)

Fig 10: Clinical picture 4 weeks after surgery. The cosmetic outcome was acceptable and feed uptake was very good (a). The wound surface had completely healed, no deposition of feed material was observed (b).

Kelly 2010). Radiotherapy has been recommended as therapy for equine cutaneous and deep-seated malignant tumours. The success is proportional to the size of the tumour and depends on the type of tumour. For example, squamous cell carcinoma is more susceptible than fibroblastic sarcoid to gamma radiation (Knottenbelt and Kelly 2010). Due to lack of an appropriate facility, radiotherapy was not available as a treatment option (Lechartier et al. 2015). In this case, surgical removal of the rostral mandible was well tolerated and the result was cosmetically satisfactory. Additional amputation of the tip of the tongue was not necessary. In retrospect, biopsy or removal of the local lymph nodes would have been advisable to decrease the risk of Fig 12: Dorsoventral radiograph 4 weeks after surgery. The border recurrence. Radiographic and histopathological examination of the bone shows no remodelling or lysis. is generally recommended early in the disease process to allow for early intervention. The rostral mandibulectomy is a rostral portion of the maxilla in horses has also been performed good option in cases with sufficient stability in the mandibular successfully (Bush et al. 2007; Cousty and Tricaud 2014; symphysis. Euthanasia should not be considered as the only Lechartier et al. 2015). We are unaware of previous reports of a option. rostral mandibulectomy as therapy of a fibrosarcoma of a In conclusion, in this case surgical treatment was horse. Only one successful partial mandibulectomy of an successful. Given the fast and good recovery of this mare, undifferentiated sarcoma in a horse has been described treatment attempts even in cases with extensive tumours and (Carmalt and Linn 2013). Frequently, the horses were subjected resulting loss of body condition due to difficulties in to euthanasia when the biopsy revealed signs of a malignant prehension, mastication or anorexia should be considered. sarcoma in oral tumours (Barber et al. 1983; Bush et al. 2007). The final outcome could have been improved had treatment Consequently, there is limited knowledge about the not been delayed. Excessive growth of the tumour resulting in progression and treatment options of equine fibrosarcoma. instability of the mandible post resection or metastases is In the reported cases, the masses were fast growing, expected to limit treatment options and worsen prognosis. locally invasive, ulcerated and caused displacement of the incisors. However, a low rate of metastasis was observed, which improves the prognosis and may result in a higher Authors’ declaration of interests success rate of treatment (Bush et al. 2007; Snyder et al. No conflicts of interest have been declared. 2008). Recurrence after surgery highly depends on the type and localisation of tumour. Carmalt and Linn (2013) described local recurrence of a poorly differentiated Ethical animal research fi brosarcoma 20 months after surgical excision. In that case, This is a retrospective study and does not require ethical histological evidence of abnormal tissue at the caudal approval. margin of the resection was reported. Recurrence was likely due to this finding. In other reports, no evidence of regrowth was reported 10 months after surgical removal of a nasal- Source of funding maxillary fibrosarcoma (Hultgren et al. 1987) and 18 months after removal of a fibrosarcoma of the tarsal groove (Story None. et al. 2005). In both reports, the affected horses were very young. Another report described no recurrence in younger Authorship horses with ossifying fibroma (Morse et al. 1988). In the case described here, the tissue mass was first noted All authors contributed equally to the study design, collecting 1 year prior to presentation at which point a sample was the data and writing and reviewing the manuscript. submitted for histopathological examination and diagnosed as inflammation. False-negative results are common with accidental biopsy of the surrounding inflammatory tissue Manufacturers' addresses (Knottenbelt and Kelly 2010). In cases with extensive 1Medistar, Germany. inflammatory tissue, a deep biopsy from the centre of the 2CP-Pharma, Germany. 3 lesion may be preferable. At the time of the biopsy, the mare Bela-Pharm, Germany. 4Serumwerk Bernburg, Germany. reportedly had a good appetite, but on presentation a year 5Arthrex, Germany. later the horse was in poor body condition and resented any 6Pfizer, Germany. manipulation of the affected region. A significant increase in 7RESORBA Medical GmbH, Germany. 8 size and osteolysis suggested malignancy. The rostral Merial, Germany. 9AniMedica, Germany. localisation of the tumour has been frequently described in 10Merck Millipore, Germany. horses and surgical therapy, local application of cisplatin and radiation has been specified as treatment attempts (Witte 2014). Intralesional chemotherapy has low success rates in References ameloblastic carcinoma (De Cock et al. 2003) but there is Barakzai, S.Z. (2010) Dental imaging. In: Equine Dentistry (Hrsg), Eds: J. little information in equine oral neoplasms (Knottenbelt and Easley, P. Dixon and J. Schumacher, Saunders, Edinburgh. pp 199-230.

Barber, S.M., Clark, E.G. and Fretz, P.B. (1983) Fibroblastic tumor of the removal of an ossifying fibroma in an 18-year-old Warmblood premaxilla in two horses. J. Am. Vet. Med. Assoc. 182, 700-702. gelding. Equine Vet. J. 27, 574-578. Bush, J.M., Fredrickson, R.L. and Ehrhart, E.J. (2007) Equine Mendez-Angulo, J.L., Tatarniuk, D.M., Ruiz, I. and Ernst, N. (2014) osteosarcoma: a series of 8 cases. Vet. Pathol. 44, 247-249. Extensive rostral mandibulectomy for treatment of ameloblastoma in a horse. Vet. Surg. 43, 222-226. Carmalt, J.L. and Linn, K.A. (2013) Large segmental mandibulectomy for treatment of an undifferentiated sarcoma in a horse. Vet. Surg. Monteiro, S., Lemberger, K. and Gangl, M. (2009) Mandibular 42, 433-439. squamous cell carcinoma in a young horse. Equine Vet. Educ. 21, Cousty, M.T. and Tricaud, C. (2014) Resection of a premaxilla and rostral 406-410. portion of the maxilla in a horse. Equine Vet. Educ. 26, 269-273. Morse, C.C.S., Salk, J.E., Richardson, D.W. and Fetter, A.W. (1988) Equine De Cock, H.E., Labelle, P. and Magdesian, K.G. (2003) Ameloblastic juvenile mandibular ossifying fibroma. Vet. Pathol. 25, 415-421. carcinoma in a horse. J. Comp. Pathol. 128, 210-215. Orsini, J.A., Nunamaker, D.M., Jones, C.J. and Acland, H.M. (1991) Dorn, C.R. and Priester, W.A. (1976) Epidemiologic analysis of oral and Excision of oral squamous-cell carcinoma in a horse. Vet. Surg. 20, pharyngeal cancer in dogs, cats, horses, and cattle. J. Am. Vet. 264-266. Med. Assoc. 169, 1202-1206. Richardson, D.W., Evans, L.H. and Tulleners, E.P. (1991) Rostral Greet, T.R., Boys Smith, S.J. and Steven, W.N. (2011) Mandibular Mandibulectomy in 5 Horses. J. Am. Vet. Med. Assoc. 199, 1179- lymphoma in a three-year-old thoroughbred filly. Vet. Rec. 168, 80. 1182. Henneke, D.R., Potter, G.D., Kreider, J.L. and Yeates, B.F. (1983) Snyder, C.D., Dubielzig, R.R., Gengler, W. and Livesey, M.A. (2008) Relationship between condition score, physical measurements and Surgical treatment of a rostral manibular complex odontoma in a body fat percentage in mares. Equine Vet. J. 15, 371-372. 3-year-old horse. Equine Vet. Educ. 20, 647-651. Hultgren, B.D., Schmotzer, W.B., Watrous, B.J., Hedstrom, O.R., Schmitz, Story, M.R., Gaughan, E.M., Andrews, G.A. and Balch, S. (2005) J.A., Wagner, P.C., Kaneps, A.J. and Gallagher, J.A. (1987) Nasal- Fibrosarcoma over the tarsal groove of a 14-month-old Quarter maxillary fibrosarcoma in young horses: a light and electron horse. Vet. Comp. Orthop. Traumatol. 18, 115-118. microscopic study. Vet. Pathol. 24, 194-196. Veraa, S., Voorhout, G. and Klein, W.R. (2009) Computed tomography Knottenbelt, D.C. and Kelly, D.F. (2010) Oral and dental tumours. In: of the upper cheek teeth in horses with infundibular changes and Equine Dentistry (Hrsg), Eds: J. Easley, P. Dixon and J. Schumacher, apical infection. Equine Vet. J. 41, 872-876. Saunders, Edinburgh. pp 149-181. Verstraete, F.J. (2005) Mandibulectomy and maxillectomy. Vet. Clin. Kutzler, M.A., Feleciano, J. and Valentine, B.A. (2007) Mandibular N. Am. Small anim. Pract. 35, 1009-1039, viii. ameloblastoma in a mare. Equine Vet. Educ. 19, 471-475. Witte, S. (2014) Maxillectomy and mandibulectomy in the horse: Lechartier, A.S., Steele, E., Vallefuoco, R. and Mespoulhes-Rivi ere, C. indications and necessity of post operative adjunct therapy. (2015) Resection of the incisive bone and rostral maxillae for Equine Vet. Educ. 26, 274-279.

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Case Report Multifocal discrete osteolysis in a horse with silicate associated osteoporosis R. Zavodovskaya†* , M. Eckert‡, B. G. Murphy§, S. M. Stover†, A. Kol§ and S. Diab# †Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California- Davis, Davis; ‡One on One Integrative Equine LLC, Modesto; §Department Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California-Davis, Davis; and #California Animal Health and Food Safety Laboratory, School of Veterinary Medicine, University of California-Davis, Davis, California, USA *Corresponding author email: [email protected]

Keywords: horse; silicosis; osteoporosis; osteoclasts; osteolysis

Summary geographically clustered in endemic regions where soils are Silicate associated osteoporosis (SAO) was diagnosed rich in cristobalite (e.g. central California coast) (Arens et al. post-mortem in an adult horse with the shortest documented 2011), and cases diagnosed in nonendemic sites had previous exposure to cytotoxic silicates of 2 years. The horse was exposure to cristobalite-rich soils. The osteoporosis comorbidity evaluated for a 6-month history of progressive back has been recognised in horses and implicated in rare reports in tenderness and acute onset of lameness. The horse had a humans (Arens et al. 2011; Yildizgoren et al. 2014, 2016). The marked (4/5) (American Association of Equine Practitioners pathogenesis of the skeletal manifestation remains unknown. scale) left forelimb lameness, moderate (2/5) hindlimb ataxia Clinical diagnosis in horses can be challenging and relies and weakness, and cervical pain upon palpation. Physical on a history of cytotoxic silicate exposure with corresponding examination did not reveal clinical skeletal deformities or clinical findings of skeletal pain and deformities, pathological respiratory compromise. Radiographs revealed widespread, fractures and occasional simultaneous respiratory discrete, sharply delineated, osteolytic lesions in the skull, compromise. Ancillary tests used to confirm silicosis and vertebral column, ribs, scapulae and middle phalanx (P2) of osteoporotic bone changes (i.e. bronchoalveolar lavage, the left forelimb and a diffuse bronchointerstitial lung pattern. lung biopsy, scapular ultrasound, radiographs, bone The presumptive clinical diagnosis was widespread, scintigraphy) can be informative, although sensitivity and metastatic osteolytic neoplasia. Due to the poor quality of life specificity are low (Anderson et al. 2008; Arens et al. 2013). and grave prognosis, the horse was humanely euthanised. Gross and histopathological post-mortem examinations Post-mortem examination revealed pulmonary silicosis in the remain the gold standard for the diagnosis of SAO. lungs and hilar lymph nodes and osteolytic lesions with Characteristic lesions in the lung and/or draining lymph nodes numerous, large osteoclasts and disorganised bone include fibrosing granulomas, central necrosis and remodelling both consistent with SAO. SAO should be intralesional refractile crystals. The cristobalite crystals included as a differential diagnosis for horses with associated with SAO can also be visualised using polarised widespread, multifocal, discrete osteolysis and history of light microscopy. Fine crystals are more readily observed with exposure to endemic regions with possible cytotoxic silicate transmission electron microscopy (Schwartz et al. 1981; Arens inhalation. Exposure time of 2 years is potentially sufficient to et al. 2011). Histological examination of the grossly deformed, develop SAO. osteoporotic bones reveals poorly demarcated areas of osteolysis, disordered remodelling and mosaic cement lines. The microscopic hallmark of SAO is the presence of Introduction numerous, large osteoclasts that create big, scattered cavities in the cortex and medullary trabeculae (Arens et al. Silicate associated osteoporosis (SAO) is an enigmatic equine 2011). Oedema, congestion, haemorrhage and loss of disorder featuring concurrent pulmonary silicosis and haematopoietic bone marrow are typically observed in areas osteoporosis (Arens et al. 2011). Silicosis is induced by of active resorption together with increased osteoblastic inhalation of cytotoxic, soil-derived crystallised particles of activity (R. Zavodovskaya, unpublished observations). silicate dioxide (e.g. cristobalite) (Arens et al. 2011). Granulomas featuring necrosis and fibrosis within the lungs and draining lymph nodes characterise the lesions induced by Case history cristobalite in horses (Schwartz et al. 1981; Arens et al. 2011). Cristobalite-induced silicosis has also been reported in people An 8-year-old Paint horse gelding presented with a 6-month and laboratory animals (Mossman and Glenn 2013). history of progressive back tenderness, resistance to saddling Osteoporosis in horses with silicosis is manifested clinically by and difficulty walking downhill. A left forelimb lameness had skeletal deformities (lateral bowing of the scapulae and ribs, progressed over 3 weeks. The horse had been living in an lordosis of the spine), skeletal pain (sensitivity to palpation, SAO endemic region for about 2 years. The gelding was neck stiffness and intermittent vague lameness) and moved to a nonendemic location where it resided for pathological fractures of osteoporotic bones (Anderson et al. approximately 6 months prior to presentation. It was used for 2008; Arens et al. 2011, 2013). SAO-affected horses are pleasure riding.

Clinical findings crystals were visualised within granulomas using polarised light At presentation, the horse had a marked (4/5) (American (Fig 2). Association of Equine Practitioners [AAEP] scale) left forelimb Gross examination of the skeleton reflected clinical lameness and mild (2/5) hindlimb ataxia and weakness. radiographic findings of numerous discrete osteolytic lesions Cervical pain was noted diffusely, bilaterally throughout the concentrated in the axial portion of the skeleton (skull, cervical region during palpation of the vertebrae and the vertebral column, ribs) and proximal portions of the articular facet joints. The horse resisted lateral flexion of the appendicular skeleton (scapulae and pelvis) (Fig 1). Rare neck. Clinical radiographs of the head, cervical, thoracic bone lesions were observed in metaphyseal and epiphyseal and lumbar vertebrae, the distal left thoracic limb and thorax regions of long bones (humerus and P2 of the left forelimb) were obtained. Widespread, discrete, sharply delineated, (Supplementary Item 1). Lesions were discolored red, circular radiolucent lesions, averaging at 1.0 cm and ranging from 0.5 to rhomboid and sharply demarcated. Similar to radiographic to rare 4.8 cm in diameter were observed throughout the findings, they averaged at 1.0 cm and ranged from 0.5 to vertebrae, ribs and visible portions of the scapulae (Fig 1). 4.5 cm in diameter (Fig 3 and Supplementary Items 1 and 2). Radiographs revealed a focal, round, 0.7 cm in diameter, On cut surface, red, spongy and friable bone replaced both subchondral radiolucency at the distopalmar aspect of the the cortical and the medullary compartments of the middle phalanx (P2) of the left forelimb (Supplementary Item examined bone specimens (Fig 3). Radiographs of dissected 1). This lesion was not evident on prepurchase radiographs specimens demonstrated the sclerotic rim around the lesions taken 10 months earlier. (Figs 1 and 3 and Supplementary Items 1 and 2). A rib Thoracic radiographs revealed a diffuse bronchointerstitial fracture callus and left stylohyoid bone had poorly defined lung pattern (Fig 2). Mild microcytic normochromic anaemia borders of osteolysis and expansion of the cortical bone with was the only abnormality identified on the complete blood porous bone (Supplementary Item 2). Impression smears of cell count and serum chemistry profile (HCT 26.6% [30–47%], the bone lesions contained mixed bone marrow cell haemoglobin 10.2 g/dL [10.7–16.5 g/dL], MCV 39.8 fL [41.1– populations along with numerous plump osteoblasts and rare 52.4], MCH 15.3 pg [14.1–18.6]). The main presumptive clinical osteoclasts. diagnosis was widespread, metastatic osteolytic neoplasia, Microscopic examination revealed clear demarcation with SAO being lower on the list of differential diagnoses. Due between osteolytic lesions and well-organised parent to the poor quality of life with progressive skeletal pain and trabecular and cortical lamellar bone tissue (Fig 3). De novo, grave prognosis, and given the primary differential diagnosis, reparative bone trabeculae characterised by labyrinthine, further tests such as biopsy were not pursued and the horse thin ribbons of intermixed woven and lamellar bone tissue was humanely euthanised. formed in the core of the lesions (Fig 3). The lesional intertrabecular stroma was predominately hypocellular, Post-mortem diagnosis oedematous, and congested (Fig 3). Microbial agents were Post-mortem examination revealed hundreds of 1–3mm not identified within skeletal or pulmonary lesions with diameter, tan, firm granulomas diffusely scattered throughout ancillary tests (Table 1). Serum was tested post-mortem with the pulmonary parenchyma (Fig 2). The hilar (tracheobronchial) electropherogram due to the radiographic similarity of the and mediastinal lymph nodes, which provide lymphatic skeletal lesions in the examined horse to the lesions in drainage from the lung, were markedly enlarged and firm due metastatic multiple myeloma, but revealed no abnormality. to central fibrosis and mineralisation. Histological changes in The diagnosis of SAO was established based on pathological the lung and lymph nodes were consistent with silicosis findings in the lungs and bones. characterised by dense, fibrous lesions with central necrosis and occasional dystrophic mineralisation, surrounded by large Discussion numbers of histiocytes and multinucleate giant cells, fewer lymphocytes and plasma cells. Sparse, refractile, angular to This case differs from previously reported SAO cases in three linear, variably sized (length – 1to3lm), intra- and extra-cellular important ways. The first distinction is that the previously

a) b) c)

Fig 1: a) Lateral radiographs demonstrated discrete, circular to ovoid osteolytic lesions (white arrow) in the angle of the mandible, b) second and third cervical vertebrae and c) thoracic spinous processes. c) Faint outlines of osteolytic lesions were visible in the overlying dorsal aspect of the scapula (outline of the dorsal border and spine of the scapular are marked with black arrows). An outer radiodense rim accentuated the osteolytic lesions throughout the skeleton.

© 2018 EVJ Ltd OSPHOS® (clodronate injection) Bisphosphonate. For use in horses only. Brief Summary (For Full Prescribing Information, see package insert) CAUTION: Federal (USA) law restricts this drug to use by or on the order of a licensed veterinarian. DESCRIPTION: Clodronate disodium is a non-amino, chloro- containing bisphosphonate. Chemically, clodronate disodium is (dichloromethylene) diphosphonic acid disodium salt and is manufactured from the tetrahydrate form. INDICATION: For the control of clinical signs associated with navicular syndrome in horses. CONTRAINDICATIONS: Horses with hypersensitivity to clodronate disodium should not receive OSPHOS. Do not use in horses with impaired renal function or with a history of renal disease. WARNINGS: Do not use in horses intended for human consumption. HUMAN WARNINGS: Not for human use. Keep this and all drugs out of the reach of children. Consult a physician in case of accidental human exposure. PRECAUTIONS: OSPHOS has been associated with renal toxicity. Concurrent administration of other potentially nephrotoxic drugs should be approached with caution and renal function should be monitored. Use of bisphosphonates in patients with conditions or diseases affecting renal function is not recommended. Horses should be well-hydrated prior to and after the administration of OSPHOS due to the potential for adverse renal events. Water intake and urine output should be monitored for 3-5 days post-treatment and any changes from baseline should elicit further evaluation. As a class, bisphosphonates may be associated with gastrointestinal and renal toxicity. Sensitivity to drug associated adverse reactions varies with the individual patient. Renal and gastrointestinal adverse reactions may be associated with plasma concentrations of the drug. Bisphosphonates are excreted by the kidney; therefore, conditions causing renal impairment may increase plasma bisphosphonate concentrations resulting in an increased risk for adverse reactions. Concurrent administration of other potentially nephrotoxic drugs should be approached with caution and renal function should be monitored. Use of bisphosphonates in patients with conditions or diseases affecting renal function is not recommended. Administration of bisphosphonates has been associated with abdominal pain (colic), discomfort, and agitation in horses. Clinical signs usually occur shortly after drug administration and may be associated with alterations in intestinal motility. In horses treated with OSPHOS these clinical signs usually began within 2 hours of treatment. Horses should be monitored for at least 2 hours following E administration of OSPHOS. Bisphosphonates affect plasma concentrations of some minerals and electrolytes such as calcium, magnesium and potassium, N immediately post-treatment, with effects lasting up to several hours. Caution should be used when administering bisphosphonates to I horses with conditions affecting mineral or electrolyte homeostasis (e.g. hyperkalemic periodic paralysis, hypocalcemia, etc.). The safe use of OSPHOS has not been evaluated in horses less L than 4 years of age. The effect of bisphosphonates on the skeleton of growing horses has not been studied; however, bisphosphonates P inhibit osteoclast activity which impacts bone turnover and may I affect bone growth. Bisphosphonates should not be used in pregnant or lactating mares, or mares intended for breeding. The safe use of OSPHOS has not C been evaluated in breeding horses or pregnant or lactating mares. Bisphosphonates are incorporated into the bone matrix, from where S they are gradually released over periods of months to years. The extent of bisphosphonate incorporation into adult bone, and hence, I the amount available for release back into the systemic circulation, is directly related to the total dose and duration of bisphospho- D nate use. Bisphosphonates have been shown to cause fetal developmental abnormalities in laboratory animals. The uptake of bisphosphonates into fetal bone may be greater than into maternal E bone creating a possible risk for skeletal or other abnormalities in the fetus. Many drugs, including bisphosphonates, may be excreted N in milk and may be absorbed by nursing animals. I Increased bone fragility has been observed in animals treated with bisphosphonates at high doses or for long periods of time. Bisphos- U phonates inhibit bone resorption and decrease bone turnover which F Q may lead to an inability to repair micro damage within the bone. In O E humans, atypical femur fractures have been reported in patients on R Y long term bisphosphonate therapy; however, a causal relationship EVER has not been established. ADVERSE REACTIONS: The most common adverse reactions reported in the field study were clinical signs of discomfort or nervousness, colic and/or pawing. Other signs reported were lip licking, yawning, head shaking, injection site swelling, and hives/pruritus. POST-APPROVAL EXPERIENCE (December 2018): The following adverse events are based on post-approval adverse drug experience reporting. Not all adverse events are reported to FDA/ The intramuscular CVM. It is not always possible to reliably estimate the adverse event frequency or establish a causal relationship to product exposure using these data. The following adverse events are listed in decreasing order of bisphosphonate injection reporting frequency: renal failure, polyuria, polydipsia, abdominal pain, anorexia, lethargy, hypercalcemia, behavioral disorder, discomfort, hyperkalemia, hyperactivity, recumbency, hyperthermia, injection site reactions, muscle tremor, urticaria, hyperglycemia, and for control of clinical signs fracture. In some cases, death has been reported as an outcome of Learn more online the adverse events listed above. associated with Navicular Syndrome INFORMATION FOR HORSE OWNERS: Owners should be advised to: www.dechra-us.com • NOT administer NSAIDs. in horses 4 years of age and older • Ensure horses have access to adequate water before and www.osphos.com after administration of OSPHOS. • Observe their horse for at least 2 hours post-treatment for signs of colic, agitation, and/or abnormal behavior. As with all drugs, side effects may occur. The most common adverse reactions reported in the field study were clinical signs • If a horse appears uncomfortable, nervous, or experiences of discomfort or nervousness, colic and/or pawing. Other signs reported were: lip licking, yawning, head shaking, injection cramping post-treatment, hand walk the horse for 15 minutes. site swelling, and hives/pruritus. Osphos should not be used in pregnant or lactating mares, or mares intended for breeding. If signs do not resolve contact the veterinarian. • Monitor water intake and urine output for 3-5 days post- Use of Osphos in patients with conditions affecting renal function or mineral or electrolyte homeostasis is not recommended. treatment. Refer to the prescribing information for complete details or visit www.osphos.com. • Contact their veterinarian if the horse displays abnormal clinical signs such as changes in drinking and urination, appetite, and attitude. CAUTION: Federal law restricts this drug to use by or on the order of licensed veterinarian. Manufactured for: Dechra Veterinary Products * Freedom of Information Summary, Original New Animal Drug Application, approved by FDA under NADA # 141-427, for OSPHOS. April 28, 2014. 7015 College Blvd., Suite 525, Overland Park, KS 66211 866-933-2472 Dechra Veterinary Products US and the Dechra D logo are registered trademarks of Dechra Pharmaceuticals PLC. © 2019 Dechra Ltd. © 2019 Dechra Ltd. OSPHOS is a registered trademark of Dechra Ltd. All rights reserved. Approved by FDA under NADA # 141-427 prioritize your health at the AVMA Trust Wellness Booth

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a) b)

A A

V V

B B

a a ca) cb)

Fig 2: a) Lateral radiograph of the caudal lung field demonstrated diffuse interstitial lung pattern. b) Miliary fibrosing granulomas (thin arrow) were scattered throughout the lung parenchyma as shown on the cut surface of the gross specimen (histology ca,b). Some of the small bronchi were plugged with mucus and inflammatory cells (thick arrow). ca) The granulomas were next to or surrounded terminal bronchi (B) characterised by numerous macrophages within abundant fibrosis. cb) Polarising filters highlighted the bright, streaming, autofluorescent fibrous bands within the granuloma. ca,b inserts) Many macrophages contained sharp fragments of crystalline particles (thick arrows), some of which were highlighted with polarisation (yellow arrow). ca) Upper left insert shows crystalline particle in a multinucleated macrophage. Alveolar (a) walls and vessels were red due to congestion. (A, arteriole; V, vein) (H&E).

reported diagnostic skeletal deformities, such as cranial and cell myeloma). Other metastatic neoplasms such as lateral bowing of the shoulders, were absent (Durham and melanoma, lymphoma, carcinoma, or Langerhans cell Armstrong 2006; Anderson et al. 2008; Arens et al. 2011). histiocytosis were lower on the list of differential diagnoses. Second, the bone lesions, while widespread, were distinctly Skeletal pain, osteolysis, and an axial and proximal multifocal and discrete; in contrast to the coalescing to appendicular distribution are common to both SAO and diffuse, poorly demarcated pattern documented previously metastatic osseous neoplasia (MacAllister et al. 1987; (Anderson et al. 2008; Arens et al. 2011; Symons et al. 2012). Edwards et al. 1993; Munoz et al. 2009). Lastly, this horse developed SAO after the shortest Biopsy or needle aspirates of the bone lesions would be documented exposure to the SAO endemic regions. useful in differentiating SAO from neoplasia for prognostic Previously, the shortest known exposure for SAO development and therapeutic purposes. Uniform populations of neoplastic was 4 years (Arens et al. 2011). Records indicated that the cells, for example plasma cells in potential multiple myeloma horse moved from Nevada (a region where SAO has not or epithelial cells in metastatic carcinoma, would rule out been reported) to California and lived 2 years in an SAO SAO. SAO bone lesion aspirates have not been endemic region known to have soils rich in cytotoxic silicate. characterised, but impression smears in the current case The horse was moved to a non-SAO endemic location contained mixed cell populations with numerous osteoblasts 6 months prior to presentation and thus developed the and occasional osteoclasts. Serum hyperglobulinaemia with described lesions within 2 years and 6 months. increased immunoglobulin paraproteins on electropherogram Widespread, radiographically discrete, radiolucent bone would be typical of myeloma (Munoz et al. 2009). lesions observed in the 8-year-old horse are most consistent Electropherogram was normal in the current case. Since with a haematogenously disseminated osteolytic disease, some horses affected with SAO respond to bisphosphonate and have not been previously reported in SAO affected therapy, treatment can be considered in other similar cases horses. Typical osteolytic lesions are poorly demarcated to where neoplasia and infection have been ruled out coalescent accompanied by bone deformity and expansion (Katzman et al. 2012). of the cortex (Arens et al. 2011). In this case, the lesions had An embolic infectious disease was considered unlikely radiographic features typical of a slowly growing, metastatic because of the absence of fever, inﬂammatory leukogram, neoplasm such as nonproductive multiple myeloma (plasma and lack of reactive bone formation and joint involvement.

* *

a) b) aa) ab)

Fig 3: The panel illustrates gross and histological features of the discrete, osteolytic lesions found predominately in the axial and proximal appendicular skeletal sites. a) Left scapula, abaxial surface, and b) lateromedial post-mortem radiograph, illustrate the numerous rounded to rhomboid, well-demarcated osteolytic lesions. b) A peri-lesional sclerotic rim is consistent with a short transition zone. aa) Closer view of the surface and ab) transverse section of one of the scapular lesions demonstrated replacement of smooth cortical surface and medullary trabecular network by friable, porous, almost spongy, bone tissue. The asterisks indicate abaxial surface of the scapula. c) Micrograph of a representative bone lesion demonstrated thick, organised trabeculae (left half of image) adjacent to a thin, labyrinthine network of intralesional trabeculae (right half of image) that make up the spongy bone. The spongy bone replaced medullary and cortical bone. Characteristic of silicate associated osteoporosis (SAO), morphologically atypical, large and numerous osteoclasts (arrows) were frequently observed at the bone surfaces (insert demonstrates the hyperactive osteoclasts seen in SAO). The stroma between the spongy bone trabeculae was marked by oedema, congestion, haemorrhage and loss of haematopoietic bone marrow. Black outlines highlighted ongoing repair of resorbed segment of trabecular bone. Note the respected boundaries between thin anastomosing trabeculae within ﬁbrous stroma and surrounding bone marrow elements in this repair (H&E).

Infectious pathogens and inflammatory cells were not from the same pathological process as the other widespread identified on post-mortem impression smears of bone lesions. discrete osteolytic lesions throughout the skeleton. The subchondral lesion in the left P2 of the thoracic limb It is possible that the discrete osteolytic lesions in this case was attributed to SAO based on gross and microscopic illustrate a previously undocumented early stage or a new findings, and post-mortem identification of grossly similar manifestation of SAO. With time, the discrete lesions might subchondral lesions associated with the coxofemoral joints. A hypothetically coalesce into the poorly demarcated regions focal degenerative joint disease process was ruled out of osteoporosis resembling the later-stage, SAO-typical because there were no accompanying degenerative joint radiographic and pathological changes associated with disease signs such as joint capsule fibrosis, joint effusion or skeletal deformities. In fact, a rib fracture callus and left synovial hyperplasia. Residual abnormality from a stylohyoid bone demonstrate the classic SAO lesions developmental disorder was considered unlikely because the (Supplementary Item 2). However, the minimal exposure time lesion was not visualised on radiographs 10 months before and dose of cytotoxic silicates necessary for the initiation and presentation. Therefore, the lesion in P2 most likely resulted development of the pulmonary and skeletal diseases remain

TABLE 1: Ancillary tests performed during investigation of this case are summarised

Test Tissue Result

KOH (potassium hydroxide) wet mount Lung impression smears Negative for fungal spherules suggestive of Coccidioides sp. Cytology (Diff-Quik) Rib osteolytic lesions impression smears Negative for infectious agents, neoplastic or inﬂammatory cells Fungal and aerobic bacterial cultures Lung and hilar lymph nodes tissues Negative growth Haematoxylin and eosin, Gram, Periodic Lung and hilar lymph nodes histological sections Negative for infectious organisms acid–Schiff (PAS), and acid fast stains Serum electrophoresis Frozen serum Normal Transmission electron microscopy (TEM) Osteolytic lesion – rib, vertebra, Putative etiological agent(s) not observed and stylohyoid bones

undetermined. Horses suffering from SAO typically present at of this diagnosis. Biopsy or cytological aspirates of the the terminal stages of osteoporosis because there currently osteolytic lesions may be helpful to rule out metastatic are no sensitive and specific methods to detect the early neoplasia. This is the first report of a case with discrete stages of the slowly progressive and mostly subclinical disease osteolysis in SAO where multifocal bone lesions are most (Arens et al. 2013). As a result, end-stage, monophasic bone consistent with an embolic rather than systemic osteolytic lesions have historically skewed our understanding of SAO process. The underlying biological variations in this horse such pathobiology to end-stage disease. as genetic background, immunological status and The macro and micro-architecture of the polyostotic, but environmental factors may influence the unique presentation distinct osteolytic lesions were consistent with embolic event(s). of this SAO case and cannot be ruled out. There is a need for The polyostotic, circumferential lesion expansion may have ante mortem diagnostic tests to identify early stages of progressed from a focus such as a vascular bed. Activation of disease, which would facilitate the epidemiological studies of osteolysis due to a systemic trigger would likely result in more risk factors. The underlying cause(s) for the dysregulated bone diffuse lesions. Curiously, the osteolytic lesions target skeletal lysis and inadequate repair in equine SAO remains unknown. sites with highly vascular and active hematopoietic bone marrow such as the spine, ribs, scapula and pelvis; similar to Authors’ declaration of interests skeletal targets of many metastatic cancers (Campbell et al. 2015). The authors declare that there were no conflicts of interest. The pattern of osteolysis and the skeletal distribution in this case broadens the possibilities of SAO pathogenesis to Ethical animal research multifocal, haematogenous ‘seeding’ of a currently undetermined SAO factor or cell with tropism for vascular The horse in this case report was humanely euthanised per and bone marrow-rich skeletal sites. The embolic pattern of the owner’s request with consultation from equine the osteolytic lesions further challenges a central pathogenic veterinarians primarily involved in its care. The horse was not tenet linking the pulmonary and skeletal lesions in SAO. euthanised for the purposes of the larger study into the Previously, chronic, excessive osteoclastic activation was described disorder. theorised to be due to circulating pro-inflammatory factors generated in the extra-skeletal silicotic granulomas (Arens Sources of funding et al. 2011). Extra-skeletal inflammatory disease-derived factors like cytokines TNFa (tumour necrosis factor alpha) This project was supported by the Center for Equine Health and/or IL1 (Interleukin-1) have been implicated in with funds provided by the State of California pari-mutuel osteoporosis comorbidity through potentiation of fund and contributions by private donors, and T32 NIH osteoclastogenesis and osteoclast activation in a number of comparative medicine training grant. conditions, including chronic obstructive pulmonary disease (COPD) (Takayanagi 2007; Chen et al. 2015). However, the Acknowledgements osteolysis in this case is not generalised, but multifocal and more consistent with an initial embolic distribution of the We thank Dr Durham (Steinbeck Country Equine Clinic, osteolytic trigger. The skeletal distribution of the bone lesions Salinas, California, USA), for providing his clinical expertise on in this case indicates targeted rather than random distribution the case. Consultations and review of the case with Dr Roy of the osteolytic trigger throughout the skeletal vascular beds. Pool (College of Veterinary Medicine, Texas A&M University, Therefore, a previous theory of skeletal dissemination of College Station, Texas USA), fueled the development of ideas silicate-laden macrophages migrating from the thorax as in this manuscript. initiators of osteolysis may need to be re-examined (Arens et al. 2011). Authorships In summary, SAO should be considered as a differential diagnosis in horses with widespread, multifocal, discrete R. Zavodovskaya contributed to the conception and design osteolytic lesions lacking fever, hypercalcaemia and serum of the study, acquisition and interpretation of data and protein alterations. Evaluation of environmental factors, such drafting the article. M. Eckert contributed to the conception, as location of farm for possible exposure to cytotoxic silicate acquisition and interpretation of clinical data and critical particles, should be pursued in the initial steps of exploration revision of the article. B. Murphy contributed to conception

and design of the study, interpretation of the data and fibrosis in horses from the Monterey-Carmel peninsula. Chest 80, 82- critical revision of the article. S. Stover and A. Kol contributed 85. to the study design, interpretation of the data and critical Symons, J.E., Entwistle, R.C., Arens, A.M., Garcia, T.C., Christiansen, revision of the article. S. Diab contributed to the conception B.A., Fyhrie, D.P. and Stover, S.M. (2012) Mechanical and morphological properties of trabecular bone samples obtained and design of the study, acquisition and interpretation of from third metacarpal bones of cadavers of horses with a bone data and critical revision of the article. All authors gave final fragility syndrome and horses unaffected by that syndrome. Am. J. approval of the version of the manuscript to be published. Vet. Res. 73, 1742-1751. Takayanagi, H. (2007) Osteoimmunology: shared mechanisms and crosstalk between the immune and bone systems. Nat. Rev. References Immunol. 7, 292-304. Anderson, J.D., Galuppo, L.D., Barr, B.C., Puchalski, S.M., Macdonald, Yildizgoren, M.T., Ekiz, T., Nadir Ozis, T., Baki, A.E., Tutkun, E. and M.M., Whitcomb, M.B., Magdesian, K.G. and Stover, S.M. (2008) Ozgirgin, N. (2014) Osteoporosis: can it be related to silicosis?. Clinical and scintigraphic findings in horses with a bone fragility Tuberk. Toraks 62, 98-99. – disorder: 16 cases (1980 2006). J. Am. Vet. Med. Assoc. 232, 1694- Yildizgoren, M.T., Ozis, T.N., Baki, A.E., Tutkun, E., Yilmaz, H., Tiftik, T., Ekiz, 1699. T. and Ozgirgin, N. (2016) Evaluation of bone mineral density and Arens, A.M., Barr, B., Puchalski, S.M., Poppenga, R., Kulin, R.M., 25-hydroxyvitamin D levels in subjects with silica exposure. Environ. Anderson, J. and Stover, S.M. (2011) Osteoporosis associated with Health Prev. Med. 21, 149-153. pulmonary silicosis in an equine bone fragility syndrome. Vet. Pathol. 48, 593-615. Arens, A.M., Puchalski, S.M., Whitcomb, M.B., Bell, R., Gardner, I.A. and Supporting information Stover, S.M. (2013) Comparison of the use of scapular ultrasonography, physical examination, and measurement of Additional Supporting Information may be found in the online serum biomarkers of bone turnover versus scintigraphy for ’ detection of bone fragility syndrome in horses. J. Am. Vet. Med. version of this article at the publisher s website: Assoc. 242, 76-85. Supplementary Item 1: (A) Dorsopalmar and (B) lateromedial Campbell, B.A., Callahan, J., Bressel, M., Simoens, N., Everitt, S., radiographs of the distal aspect of the left forelimb Hofman, M.S., Hicks, R.J., Burbury, K. and MacManus, M. (2015) demonstrate a focal, round, 7 mm in diameter, subchondral Distribution atlas of proliferating bone marrow in non-small cell lung cancer patients measured by FLT-PET/CT imaging, with potential radiolucency at the distopalmar aspect of P2 (arrows). (C) applicability in radiation therapy planning. Int. J. Radiat. Oncol. Focal depression of the articular cartilage of the P2 with Biol. Phys. 92, 1035-1043. destruction of subchondral bone was identified during Chen, S.J., Liao, W.C., Huang, K.H., Lin, C.L., Tsai, W.C., Kung, P.T., necropsy. Insert shows the collapse of articular cartilage and Chang, K.H. and Kao, C.H. (2015) Chronic obstructive pulmonary lysis of subchondral plate (arrows). (The specimen was disease is a strong independent risk factor for osteoporosis and sectioned during pathological examination creating central pathologic fractures: a population-based cohort study. QJM 108, 633-640. fissure and discoloration artifacts). (D) The osteolytic Durham, M. and Armstrong, C.M. (2006) Fractures and bone subchondral lesion in the sectioned gross specimen was deformities in 18 horses with silicosis. Proc. Am. Assoc. Equine examined histologically. The lesion had SAO-typical Practnrs. 52, 311–317. morphological changes with atypical osteoclasts (thin arrows, Edwards, D.F., Parker, J.W., Wilkinson, J.E. and Helman, R.G. (1993) insert) and labyrinthine bone remodelling. Similar to other sites Plasma cell myeloma in the horse. A case report and literature of osteolysis, the lesion was well-demarcated from normal review. J. Vet. Intern. Med. 7, 169-176. surrounding bone. Articular cartilage (ac) was fibrillated and Katzman, S.A., Nieto, J.E., Arens, A.M., MacDonald, M.H., Puchalski, regionally lost during processing. A fragment of articular S.M., Galuppo, L.D., Snyder, J.R., Maher, O. and Bell, R.J. (2012) Use cartilage herniated into the subchondral space (c). (H&E) of zoledronate for treatment of a bone fragility disorder in horses. J. Am. Vet. Med. Assoc. 240, 1323-1328. Supplementary Item 2: The panel of gross and radiographic MacAllister, C., Qualls Jr, C., Tyler, R. and Root, C.R. (1987) Multiple features of lesions in a rib – (A) (left) with a fracture callus myeloma in a horse. J. Am. Vet. Med. Assoc. 191, 337-339. and a lesion in the left stylohyoid bone (B) (right) are shown. Mossman, B.T. and Glenn, R.E. (2013) Bioreactivity of the crystalline The typical features of SAO included variably defined edges silica polymorphs, quartz and cristobalite, and implications for occupational exposure limits (OELs). Crit. Rev. Toxicol. 43, 632-660. of osteolysis and expansion of the affected cortex with porous bone present in both specimens (white arrows). (Aa, Munoz, A., Riber, C., Trigo, P. and Castejon, F. (2009) Hematopoietic neoplasias in horses: myeloproliferative and lymphoproliferative Ba) Radiographs of the specimens demonstrate cortical disorders. J. Equine Sci. 20, 59-72. expansion with porous bone and variable definition of the Schwartz, L.W., Knight, H.D., Whittig, L.D., Malloy, R.L., Abraham, J.L. margins of the lesions. Both typical and discrete SAO lesions and Tyler, N.K. (1981) Silicate pneumoconiosis and pulmonary are shown in the rib.

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Case Report Head and neck abscessation and thrombophlebitis following cheek tooth extraction in a pony A. A. Horbal†* , R. J. M. Reardon†, T. Froydenlund† , R. C. Jago‡ and P. M. Dixon† †Equine Hospital, University of Edinburgh; and ‡Royal (Dick) School of Veterinary Studies, University of Edinburgh, Roslin, Midlothian, UK

*Corresponding author email: [email protected] Dr. A. A. Horbal’s present address: University Veterinary Specialists, Pittsburgh, Pennsylvania, USA

Keywords: horse; dentistry; secondary infection; exodontia; alveolar infection; thrombectomy

Summary related to the spread of dental pathogens have been well Due to their long hypsodont reserve crowns, extraction of described in humans and in small animals (Tou et al. 2005; equid cheek teeth can be difficult and result in more Westermeyer et al. 2013). This report describes deep complications than the extraction of their shorter brachydont abscessation of the masseter muscles followed by extensive counterparts although the more recent resumption of oral thrombophlebitis of the jugular, facial and rostral cervical veins extraction has greatly reduced such complications. The more following oral cheek tooth extraction in a pony affected by common post-extraction sequelae in equids include non- pituitary pars intermedia dysfunction (PPID) that was healing alveoli due to retained dental or alveolar sequestrae successfully treated by abscess drainage and thrombectomy which may lead to oromaxillary or oronasal fistula formation, of the affected veins. chronic external sinus tract formation or osteomyelitis of the supporting bones. Collateral damage to adjacent teeth has Case report also occasionally been reported during dental repulsion. Systemic complications following equine cheek tooth A 16-year-old Welsh Pony mare in lean body condition extraction have been infrequently described, including a (302 kg body weight; body condition score 2/5) was referred small number of cases of exodontia-related bacterial to the Royal (Dick) School of Veterinary Studies Equine meningioencephalitis. This is surprising, as dental manipulation Hospital 10 days following partial extraction of cheek tooth can lead to bacteraemia in many species, including horses. 410 due to severe periodontal disease. There was no Infections at distant sites related to the spread of dental evidence of apical infection in this tooth. The pony had pathogens have been well described in humans and in small undergone successful management of clinical signs 1 animals. This report describes deep abscessation of the associated with PPID for 2 years with oral pergolide therapy masseter muscles followed by extensive thrombophlebitis of (Prascendâ Tablets) (0.5–1 mg per os once daily). Within the jugular, facial and rostral cervical veins following oral 2 days of the dental extraction, the pony developed cheek tooth extraction in a pony affected by pituitary pars significant swelling of the caudal aspect of the right intermedia dysfunction (PPID) that was successfully treated by mandible, became unable to masticate and quickly began abscess drainage and thrombectomy of the affected veins. to lose weight. Initial examination following referral revealed the pony to be tachycardic (heart rate 76 beats/min) and tachypnoeic Introduction (respiratory rate 28 breaths/min) but normothermic (37.6°C). Due to their long reserve crowns, extraction of equid The pony’s mucous membranes were pink but tacky, and no hypsodont cheek teeth can be difficult and result in more gastrointestinal borborygmi were audible. A firm swelling was complications than the extraction of their shorter brachydont present over the right masseter, along with subcutaneous counterparts although the more recent resumption of oral pitting oedema coursing dorsally from the angle of the extraction has greatly reduced such complications (Dixon mandible up to the base of the right ear. et al. 2005). The more common sequelae after exodontia in Following profound sedation (0.04 mg/kg bwt romifidine 1 â 2 equids include non-healing alveoli due to retained dental or hydrochloride [Sedivet ] and 0.025 mg/kg bwt butorphanol â alveolar sequestrae, oromaxillary or oronasal fistula formation, [Butador ] i.v.) and placement of an oral speculum, the chronic external sinus tract formation, osteomyelitis of the pony’s mouth could not be opened more than 4 cm at the supporting bones and collateral damage to adjacent teeth incisor biteplates due to the significant masseter swelling and (Dixon et al. 2008). associated pain. Oral examination was consequently Systemic complications following equine cheek tooth performed with an oral endoscope, which showed food extraction have been infrequently described, including a packed into both cheeks and some sharp maxillary cheek small number of cases of exodontia-related bacterial teeth overgrowths. Additionally, the 307 and 409 cheek teeth meningioencephalitis (Smith et al. 2004; Bach et al. 2014). This were absent, with well-healed alveoli. Root fragments of the is surprising, as dental manipulation can lead to bacteraemia recently extracted 410 tooth remained within the alveolus in many species, including horses (Nieves et al. 1997; Kinane that was lined with brown-coloured bone on its buccal et al. 2005; Bienert-Zeit et al. 2015). Infections at distant sites aspect, consistent with the appearance of a non-healing

overnight and the pony continued with antibiotic and anti- inflammatory treatment. Over the following 3 days, the pony gradually became brighter with a slightly increased appetite for soft mashes; however, a subjective increase in stiffness and sensitivity around the right side of the neck was then noted. Closer examination revealed a firm tubular swelling to be present in the right jugular groove, and ultrasonography 5 days after initial presentation revealed the right jugular vein to be thrombosed along its length from the cranial bifurcation to the level of the base of the neck with focal anechoic lesions throughout. The doxycycline medication was discontinued and intravenous ceftiofur4 (Cefenil 50 mg/ mL) (2.2 mg/kg bwt i.v. twice daily) and enteral metronidazole6 (Metronidazole 400 mg tablets) (20 mg/kg bwt per os three times daily) therapy were commenced. Computed tomography of the head performed under standing sedation on Day 5 corroborated the oral findings. The 307, 409 cheek teeth were absent, with root fragments of 410 remaining, which did not show evidence of apical infection (Fig 2). The lamina dura surrounding the 410 fragments appeared to be sclerotic. There was marked soft tissue swelling of the right masseter muscle adjacent to the 409 and 410 alveoli, but with negligible changes in the Fig 1: Exposed buccal alveolar bone in 410 alveolus, with two adjacent mandibular bone, showing that the detected root fragments also visible. alveolar osteitis did not extend deeper into the mandibular bone and that direct penetration of the alveolus had not alveolus (alveolar osteitis or ‘dry socket’)(Fig 1). Alveolar caused the masseter infection. The swollen right masseter curettage showed this exposed bone to be well attached to muscle contained multiple hypodense lesions suggestive of mandible, distinguishing it from the more common equine fluid-filled abscess cavities (Fig 3). The right linguofacial vein post-extraction alveolar bone sequestration, where the was hyperdense, consistent with thrombosis, in addition to the fragment is typically unstable and easily removed. The adjacent jugular thrombophlebitis. There was a small amount alveolus was temporarily packed with saline moist gauze to reduce food impaction in the alveolus. All dental overgrowths were then reduced using motorised floats as much as possible without risking pulpar exposure. Initial haematology revealed a mild haemoconcentration (packed cell volume 42%) and hyperproteinaemia (serum protein 82 g/L) along with a mild hyperlactataemia (whole blood lactate 2.2 mmol/L). A left jugular venous catheter was placed aseptically. Courses of enteral doxycycline3 (KaridoxTM 100 mg/ mL Oral Solution) (10 mg/kg bwt per os twice daily) and intravenous flunixin meglumine4 (Flunixin 50 mg/mL Solution for Injection) (1 mg/kg bwt twice daily) were commenced, with pergolide therapy continued. Initial treatment also included intravenous polyionic fluid therapy5 (VetivexTM 11 Hartmann’s solution). In the hours immediately following presentation, the pony became pyrexic (temperature 40°C) and increasingly tachycardic (heart rate 80 beats/min). Investigations for a source of sepsis beyond the oral cavity including abdominal ultrasonography were unremarkable. Packed cell volume and serum protein were relatively unchanged. Examination per rectum was unremarkable; however, some mucosal haemorrhage was evident following palpation. This was examined in further detail via proctoscopy, and a definitive source of haemorrhage was never identified. Further haemorrhage was not noted, and repeat proctoscopy several days later revealed no further blood within the rectum. However, abdominocentesis was performed on the evening of presentation to investigate potential peritoneal involvement in the pony’s pyrexia which yielded slightly turbid fluid with a normal total protein (5 g/L) and lactate Fig 2: Dental fragments in the 410 alveolus (arrow) with adjacent (0.9 mmol/L). Her clinical parameters gradually improved soft tissue swelling.

Fig 4: Hypoechoic lesions in the right masseter (arrows).

Fig 3: Hypodense lesions in the swollen right masseter muscle (arrows). of fluid within the right tympanic bulla, possibly consistent with otitis media due to local inflammation. After 2-day therapy with ceftiofur and metronidazole, the generalised masseter swelling began to reduce, along with mild improvements in the patient’s appetite and reduced pyrexia. A more focal, painful swelling then developed on the ventrolateral aspect of the angle of the right mandible. Ultrasonography 9 days after presentation revealed multiple, conjoined hypoechoic regions within the muscle consistent with the computed tomography findings, and once again supporting the likelihood of abscess formation (Fig 4). Ultrasound-guided needle aspiration of this site yielded dark brown, purulent material. The abscess was then surgically drained via a short horizontal incision below the ventral buccal nerve, and the affected area of necrotic muscle was gently debrided with a curette. Ultrasonography 3 days later revealed a further hypoechoic pocket adjacent to the mandible (Fig 5) that was also drained and debrided. The pyrexia and tachycardia began to resolve, and the patient’s Fig 5: Appearance of the masseter 3 days after initial abscess drainage; arrow at small hypoechoic fluid pocket remaining in demeanour and appetite improved considerably. Enriched the muscle which was later drained. aerobic, fungal, yeast and anaerobic cultures of the masseter aspirate did not yield an isolate. In contrast to the resolving masseter swelling, a more ultrasonography (Fig 6). The lumen of the jugular vein was painful swelling developed over the right jugular, maxillary filled with mixed echogenic material occluding the vessel, and linguofacial veins in the 12 days following presentation and the surrounding subcutaneous tissues appeared to be which were confirmed to be related to thrombophlebitis on thickened and hypoechoic with a cobble-stone

a) b) c)

R LFV R JUG

R max v

Fig 6: a) Septic thrombus in right maxillary vein (R MAX V). Parotid salivary gland (arrow). b) Septic thrombus in right linguofacial vein (R LFV). c) Septic thrombus in right jugular vein (R JUG). appearance, suggestive of cellulitis and oedema. Two isotonic fluids. The jugular and external maxillary vein incisions subcutaneous abscesses in the temporomandibular region were also found to communicate with the abscesses in the then ruptured and drained without intervention. Due to the temporomandibular region via bifurcating vascular structures. continued pain and abscess formation within the thrombosed Penrose drains were placed through the surgical incisions into right jugular, maxillary and linguofacial veins, a the lumen of the jugular vein (Fig 10). thrombectomy was elected to expedite recovery and Post-operatively, antimicrobial and NSAID therapy was prevent further local or systemic spread of infection (Fig 7). continued. The surgical sites were frequently cleaned and Preoperative upper respiratory tract endoscopy revealed any further exudate expressed through the incisions as they right arytenoid abduction to be slightly asymmetric and healed, and the adjacent skin was treated with petroleum asynchronous (Havemeyer Grade II.2), likely due to jelly to prevent scalding. The facial swelling resolved quickly inflammation adjacent to the right recurrent laryngeal nerve. although some focal parotid swelling persisted. Three weeks Purulent discharge was observed emanating from the right later, the mouth could now be opened almost normally. Oral guttural pouch ostium (Fig 8) and on endoscopy was found examination showed the alveolar packing to be absent and to be emanating from a soft tissue swelling, likely an inflamed healthy granulation tissue covering much of the prior site of lymph node on the lateral wall of the pouch (Fig 9). alveolar osteitis. The retained root fragments that were firmly Subsequent PCR tests of a guttural pouch lavage sample attached, without gross infection, were extracted with were negative for Streptococcus equi subspecies equi. curettes. The pony maintained a good appetite, and forage Two weeks after initial hospitalisation, ultrasound-guided feed was slowly reintroduced with minimal quidding evident. thrombectomy was performed under standing sedation and Purulent discharge from the sites reduced steadily and the local infiltration of lignocaine4 (Lignocaine and Adrenaline Injection). Four short incisions were made through the skin, subcutaneous tissues and vascular wall along the length of the right jugular and external maxillary vein and large quantities of liquid and inspissated pus were drained. The tracts were then curetted and thoroughly lavaged with

Fig 7: Ruptured abscess in the temporomandibular region (white Fig 8: Purulent material emanating from the right guttural pouch arrow) along with several stab incisions (red arrows) used to ostia, consistent with empyema and right-sided laryngeal perform the thrombectomy along the jugular groove. dysfunction.

Fig 10: Placement of Penrose drains through thrombectomy incisions.

vessels and nerves, disease may spread via lymphatics, Fig 9: Mass and purulent discharge in lateral compartment of haematogenously or via cranial nerves. Additionally, disease right guttural pouch. may be spread via osteitis and bony erosion or direct head trauma (Smith et al. 2004; Bach et al. 2014). More specifically, Penrose drains were removed 1 week following surgery. All as suspected in a case of septic thrombophlebitis associated antimicrobial and anti-inflammatory medication was with buccal ulceration, oral trauma can lead to local tissue discontinued 4 weeks following admission. infection that could spread to the adventitial tissues and The pony was discharged from hospital 6 weeks following subsequently to underlying vascular walls, both leading to initial presentation without any further medication at which adhesion and providing a substrate for the bacteria to time there was still a smaller area of exposed alveolar bone proliferate (Matsuda et al. 2010). remaining. Communications with the owner and referring In the current case, there was no apical infection with veterinary surgeon up to 14 months after the initial diagnosis alveolar bone penetration as commonly occurs with cheek confirmed the pony had required no further treatment teeth apical infections in young horses, nor was there any CT following hospital discharge and was systemically well. A or ultrasonographic evidence of direct spread of infection routine dental examination 11 months following initial through the buccal aspect of the damaged alveolar bone to presentation showed the affected alveolus to be fully healed. the masseters. The masseter infection developed within 2 days of the extraction. It is therefore possible that infection Discussion may have spread from infected periodontal tissues during extraction via lymphatic drainage to the masseteric spaces, Systemic or distant infection following oral cheek tooth and the thrombophlebitis likely started at this site. extraction has rarely been reported in horses. It has recently Alveolar osteitis is a unique process in the dental tissues been shown that a transient bacteraemia occurs in all and does not have a similar appearance clinically or equine cheek tooth extractions (Bienert-Zeit et al. 2015). radiographically to osteitis as diagnosed in other regions of When these bacteria can be cultured, they have been found the body. While the alveolar bone itself is relatively quiescent, to be common oral cavity isolates that likely are released into the diagnosis of alveolar osteitis on oral examination occurs the bloodstream immediately following gingival disruption. when the bone is exposed, with little coverage by either a This bacteraemia is usually spontaneously cleared prior to the blood clot or gingival tissue post-extraction. In this case, the end of the extraction process (Bienert-Zeit et al. 2015), but its localised alveolar osteitis could have been predisposed by occurrence potentially leads to an increased risk of pre-existing deep periodontal disease with a traumatic septicaemia and spread of infection to distant sites. extraction by the general practitioner during which both roots Although infection at distant sites has seldom been were fractured and retained, as bacterial infection of the recorded following equine dental extraction, several other periodontal tissues prior to extraction is noted to be a risk seemingly unrelated disease processes have actually been factor for the development of alveolar osteitis in humans. attributed to surgery or injury of the head region. Bacterial However, there is no consensus on whether retained dental meningitis and brain abscessation have been recorded or alveolar fragments contribute to alveolar osteitis nor on its following primary sinus, nasal, submandibular and periocular treatment in other species (Kolokythas et al. 2010; Dias and infection (Smith et al. 2004). Additionally, thrombophlebitis de Lacerda Neto 2013). Similar reports have not been associated with buccal ulceration has been reported in the reported or published in horses. The alveolar osteitis in this horse (Matsuda et al. 2010). The spread of dental or case had largely resolved in 6 weeks, and it is unclear paranasal sinus infection may occur through several routes whether the intensive antibiotic therapy the horse into systemic circulation. Due to the proximity of many major concurrently received for its soft tissue infections was of value.

Sinus and oral surgery are contaminated procedures in broad-spectrum antibiotic treatment along with clinical any species and may induce local necrosis and release of improvement of the pony even prior to thrombectomy. proteolytic enzymes that facilitate local spread of infection. In Despite factors that may have predisposed the pony to addition, the haemorrhage common with procedures systemic complications following extraction, the occurrence of performed in the head and sinuses with subsequent blood such serious sequelae was still unexpected. Post-operative clot formation can facilitate bacterial invasion. Marked tissue complications following oral extraction of a cheek tooth were injury can also cause endotoxin release which eventually recorded in only 8% of cases and only involved the alveolus activates the clotting and fibrinolytic cascades and leads to and directly associated structures such as the nasal cavity and a change in systemic resistance to disease (Bach et al. 2014). maxillary or mandibular bone in one study (Dixon et al. 2005). In fact, it is even more surprising that more horses with sinus or Complication rates of 0–4% were reported in horses over 11 and dental infections do not experience spread of infection to 9 years in age, respectively, with no report of local or systemic the cranial and cervical region, as 0.5–24% of human disease (Tremaine 1997). Even in cases of intractable and intracranial disease has been attributed to primary sinus unresolved dental sinusitis, there are no reports of associated disease (Smith et al. 2004). systemic disease (Tremaine and Dixon 2001). However, 13–23% In horses, the development of thrombophlebitis, defined of humans with periodontal disease develop bacteraemia as vascular inflammation along with thrombus formation, may following periodontal treatment. Even more significantly, nearly be directly related to a decrease in systemic resistance to 7% of humans with periodontal disease are reportedly affected disease along with alterations in fibrinolysis attributable to by a continuous low-level bacteraemia on a daily basis (Kinane systemic disease inducing a hypercoaguable state (Dias and et al. 2005). However, the prevalence of systemic disease de Lacerda Neto 2013). Along with vessel injury and venous related to this bacteraemia is extremely low. In human stasis, this is known as the ‘Triad of Thrombosis’ (Sellon and medicine, it is theorised that patients affected by severe Wise 2010). In horses, this is most commonly found in cases of periodontal disease can clear odontogenic bacteria from their gastrointestinal disease, hypoproteinaemia, salmonellosis or bloodstream more quickly as their immune systems are virtually endotoxaemia, but can be found in any case with an ‘primed’ to deal with this bacterial insult from continuous increased inflammatory response and decreased fibrinolysis. penetration through damaged gingiva (Kinane et al. 2005). This Septic thrombophlebitis then develops when the vessel wall is proposed immune response upregulation may also explain the colonised by bacteria. Additionally, equids are more at risk if lack of systemic infection due to dental disease found in they have experienced an injection of an irritating substance, equids, as Baker reported a significant proportion of horses over been injected using poor venepuncture technique or have 15 years old to be affected by significant periodontal disease experienced prolonged jugular catheterisation (Dias and de without any report of accompanying systemic disease (Baker Lacerda Neto 2013). Despite these recognised risk factors, this 1970). More recent surveys have confirmed this finding, with patient’s right jugular vein was not subjected to 44% of diastemata affected by periodontal disease without venepuncture at the R(D)SVS, and there was no evidence of associated reports of systemic illness (Walker et al. 2012). external or superficial trauma to the area surrounding the site Additionally, out of 202 horses which underwent mechanical of thrombophlebitis. Therefore, it is more likely that it was widening procedures to treat diastemata affected by severe caused by a direct spread of infection from the vasculature periodontal disease, none had reportedly experienced any of the infected masseters. systemic complications (Dixon et al. 2014). An additional inciting factor to this unusual extension of In this case, it is proposed that extraction-related damage dental infection may be related to the pituitary pars and subsequent loss of blood supply to the alveolar bone led intermedia dysfunction. The pony’s ACTH levels appeared to impaired alveolar healing. This in turn led to a localised to be well controlled with oral pergolide, however alveolar osteitis that, in this pony, led to masseter and reportedly 35% of horses affected by PPID still experience subsequent linguofacial vein infection tracking to the jugular opportunistic infections as opposed to 11% of the general vein leading to thrombophlebitis and septic cellulitis. aged equine population. Horses affected by PPID also fl have a higher baseline in ammatory state and decreased Authors’ declaration of interests ability to respond to immune challenges when compared with healthy adult horses (MacFarlane 2011). These factors The authors declare no potential conflicts of interest with may have led to an opportunistic post-extraction infection respect to the research, authorship and/or publication of this and uninhibited spread of bacteria in this pony, both article. increasing the risk of thrombus formation and subsequent infection. Ethical animal research Culture of the abscess fluid failed to produce any significant growth of bacteria. This could be for multiple Informed client consent was obtained for every diagnostic reasons, including the pony’s prior treatment with antibiotics, and treatment procedure performed in relation to this case. or the difficulty of culturing anaerobic organisms in standard culture media. As the pony responded minimally to treatment Source of funding with oral doxycycline and continued to be affected by opportunistic infection, along with a lack of culture results to None. confirm the primary pathogens involved, treatment with a third-generation cephalosporin (ceftiofur) along with Authorship metronidazole was deemed to be essential to adequately treat the pony. Culture of the thrombus material itself was not All authors contributed to interpretation of diagnostics, case performed after thrombectomy due to even more prolonged care, decisions regarding progression of case and treatment

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planning, and preparation of manuscript. All authors gave Kinane, D.F., Riggio, M.P., Walker, K.F., MacKenzie, D. and Shearer, B. their final approval of manuscript. (2005) Bacteraemia following periodontal procedures. J. Clin. Periodontol. 32, 708-713. Kolokythas, A., Olech, E. and Miloro, M. (2010) Alveolar osteitis: a Manufacturers' addresses comprehensive review of concepts and controversies. Int. J. Dentistry 2010, 1-10. 1 Boehringer Ingelheim Limited, Bracknell, Berkshire, UK. MacFarlane, D. (2011) Equine PPID. Vet. Clin. N. Am. Equine 27, 93-113. 2Chanelle Animal Health, Liverpool, UK. 3Nimrod Veterinary Products Ltd, Moreton-in-Marsh, Gloucestershire, UK. Matsuda, K., Suzuki, H., Tsunoda, N. and Taniyama, H. (2010) Jugular 4Norbrook Laboratories (GB) Limited, Corby, Northamptonshire, UK. thrombophlebitis developed from buccal ulcer in a thoroughbred 5Dechra Limited, Stoke-on-Trent, Staffordshire, UK. horse. J. Vet. Med. Sci. 72, 913-915. 6 Almus Pharmaceuticals, Chessington, Surrey, UK. Nieves, M., Hartwig, P., Kinyon, J.M. and Riedesel, D.H. (1997) Bacterial isolates from plaque and from blood during and after routine dental procedures in dogs. Vet. Surg. 26, 26-32. References Sellon, D.C. and Wise, L.N. (2010) Disorders of the hematopoietic Bach, F.S., Bodo, G., Kuemmerle, J.M., Bienert-Zeit, A., Hainisch, E.K. system. In: Equine Internal Medicine, 3rd edn., Eds: S.M. Reed, W.M. and Simhofer, H. (2014) Bacterial meningitis after sinus surgery in Bayly and D.C. Sellon, Saunders, St. Louis, Missouri. pp 730-776. fi ve adult horses. Vet. Surg. 43, 697-703. Smith, J.J., Provost, P.J. and Paradis, M.R. (2004) Bacterial meningitis Baker, G. (1970) Some aspects of equine dental disease. Equine Vet. and brain abscesses secondary to infectious disease processes J. 2, 105-110. involving the head in horses: seven cases (1980-2001). J. Am. Vet. Med. Assoc. 224, 739-742. Bienert-Zeit, A., Kern, I., Verspohl, J., Rohde, J. and Bartmann, C.P. (2015) Evidence of bacteraemia in antibiotically untreated horses Tou, S.P., Adin, D.B. and Castleman, W.L. (2005) Mitral valve before, during and after tooth extraction. Proceedings of the endocarditis after dental prophylaxis in a dog. J. Vet. Intern. Med. 24th European Congress of Veterinary Dentistry 2015, Ghent, 19, 268-270. p 156. Tremaine, W.H. (1997) Oral extraction of equine cheek teeth: A Dias, D.P.M. and de Lacerda Neto, J.C. (2013) Jugular Victorian technique revisited. Proceedings of the 5th World thrombophlebitis in horses: a review of fibrinolysis, thrombus Veterinary Dental Congress, Birmingham. pp 139-142. formation, and clinical management. Can. Vet. J. 54, 65. Tremaine, W.H. and Dixon, P.M. (2001) A long-term study of 277 cases Dixon, P.M., Dacre, I., Dacre, K., Tremaine, W.H., McCann, J. and of equine sinonasal disease. Part 2: treatments and results of Barakzai, S. (2005) Standing oral extraction of cheek teeth in 100 treatments. Equine Vet. J. 33, 283-289. horses (1998-2003). Equine Vet. J. 37, 105-112. Walker, H., Chinn, E., Holmes, S., Barwise-Munro, L., Robertson, V., Dixon, P.M., Hawkes, C. and Townsend, N. (2008) Complications of Mould, R., Bradley, S., Shaw, D.J. and Dixon, P.M. (2012) equine oral surgery. Vet. Clin. N. Am. Equine 24, 499-514. Prevalence and some clinical characteristics of equine cheek teeth diastemata in 471 horses examined in a UK first-opinion Dixon, P.M., Ceen, S., Barnett, T., O’Leary, J.M., Parkin, T.D. and equine practice (2008 to 2009). Vet. Rec. 171, 44. Barakzai, S. (2014) A long-term study on the clinical effects of mechanical widening of cheek teeth diastemata for Westermeyer, H., Ward, D., Whittemore, J.C. and Lyons, J.A. (2013) treatment of periodontitis in 202 horses (2008-2011). Equine Vet. Actinomyces endogenous endophthalmitis in a cat following J. 46, 76-80. multiple dental extractions. Vet. Ophthalmol. 16, 459-463.

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Case Report Suspected case of hypersplenism as a cause of anaemia, thrombocytopenia and leucopenia in a Miniature Horse gelding R. E. Ruby†*, D. M. Wong† , B. A. Sponseller† and M. Yaeger‡ †Department of Veterinary Clinical Sciences, Lloyd Veterinary Medical Center; and ‡Department of Veterinary Pathology, College of Veterinary Medicine, Iowa State University, Ames, Iowa, USA *Corresponding author email: [email protected]

Keywords: horse; bone marrow; immune-mediated; neutropenia; pancytopenia; platelet; spleen; splenomegaly

Summary Case history A 23-year-old Miniature Horse gelding was presented to the A 23-year-old 140 kg Miniature Horse gelding was presented Lloyd Veterinary Medical Center with a 3-week history of to the Lloyd Veterinary Medical Center with a 3-week history decreased appetite, lethargy and mild intermittent colic. A of decreased appetite, lethargy and mild intermittent colic. complete blood count revealed leucopenia, characterised Relevant medical history included a presumptive diagnosis by neutropenia and lymphopenia, as well as anaemia, and treatment (pergolide 0.00357 mg/kg bwt, q. 24 h per os) thrombocytopenia and hyperproteinaemia whereas hyper- of pituitary pars intermedia dysfunction (PPID) approximately fi triglyceridaemia was noted on serum biochemistry pro le. 1 month ago by the horse’s regular veterinarian as well as a Bone marrow evaluation was nondiagnostic and the horse brief episode of enteritis 7 years prior that resolved with was negative for antiplatelet antibody testing, Coombs medical therapy. The horse was reportedly normal in test, equine infectious anaemia virus and Anaplasma between episodes. phagocytophilum. The horse was hospitalised for 36 days On initial examination for the current presentation, the and received supportive care, antibiotics, corticosteroids, horse was quiet with tachycardia (64 beats/min), fl dextrose-containing uids and a whole blood transfusion. tachypnoea (60 breaths/min) and a rectal temperature of Following initial improvement and stabilisation, the horse 37.8°C. Hydration appeared adequate with the only became severely anaemic and acutely recumbent on abnormal clinical observations being a long hair coat and Day 36 and was subjected to euthanasia. Post-mortem mild lethargy. A cursory abdominal and thoracic ultrasound examination provided a diagnosis of hypersplenism with a examination did not reveal any abnormal features and the markedly enlarged spleen along with histiocytic phagocytosis only abnormal finding noted on abdominal and thoracic of erythrocytes and platelets. Examination of bone marrow radiographs was a small amount of sediment, likely sand, in showed appropriate erythroid hyperplasia and no evidence the ventral colon. Examination of abdominal fluid collected fi of myelopthisis or neoplasia. This report describes the rst via abdominocentesis was normal. A complete blood count presumptive case of primary hypersplenism in an equid as a revealed leucopenia, characterised by neutropenia and cause of pancytopenia. lymphopenia, as well as anaemia, thrombocytopenia and hyperproteinaemia (Table 1) whereas serum biochemistry analysis revealed hyponatraemia (134 mmol/L; reference Introduction range 137–145 mmol/L), hypochloraemia (89 mmol/L; Pancytopenia is rarely encountered in horses but when reference range 102–114 mmol/L) and hypertriglyceridaemia observed, can result from myelophthisic diseases, immune- (37.4 mmol/L; reference range <1.13 mmol/L). The plasma mediated disorders or as a consequence of infection by ACTH and insulin concentrations were 227 pg/mL (reference equine piroplasmosis or equine granulocytic anaplasmosis range 9–35 pg/mL) and 83.4 pmol/L (reference range 69.5– (Ringger et al. 1997; Dziegiel et al. 2013; Wise et al. 2014). A 278 pmol/L), respectively, suggesting that the horse had PPID. further consideration for pancytopenia, not yet described in Initial rule-outs for pancytopenia included immune- the equine literature, is hypersplenism. Hypersplenism can be mediated disease, myelophthisis, neoplasia and infection with caused by a variety of diseases which, in turn, affects equine infectious anaemia virus. The horse was administered prognosis. This disorder is characterised by an enlarged i.v. maintenance fluids (60 mL/kg/day) supplemented with spleen which causes rapid and premature destruction of 50% dextrose, for a final concentration of 2.5% dextrose, blood cells, resulting in peripheral cytopenias. Mechanisms for 24 hours. In consideration of a hapten-induced immune- causing hypersplenism include retention of blood cells within mediated disease, administration of pergolide was temporarily the spleen, phagocytosis and autoimmunity (Lv et al. 2016). discontinued. The horse remained stable over Day 1 and To the authors’ knowledge, hypersplenism has not been the appetite, attitude and faecal production were described in horses, but should be considered in clinical considered normal. Dexamethasone (0.07 mg/kg bwt, i.v.) cases of pancytopenia in which other causes are eliminated. was administered on Day 2 as a treatment for possible The case described here is the first to detail the clinical immune-mediated disease. Over the next 2 days, the horse course of disease of a Miniature Horse where hypersplenism was stable, but the haematocrit and platelet count declined was diagnosed via post-mortem examination. If an ante to 14.5% and 6000 platelets/lL, respectively, while the mortem diagnosis could have been established, splenectomy triglyceride concentration declined to 20.7 mmol/L. On Day might have been curative. 4, a bone marrow aspirate was collected from the sternum

TABLE 1: Clinicopathologic results of a 23-year-old Miniature Horse gelding over a 36-day hospitalisation period

Day

Test 1 2 3 4 5 8 10 14 21 30 32 36 Ref Interval

WBC (9109/L) 2.32 2.46 2.88 3.08 3.19 2.45 3.24 4.40 3.76 3.01 3.03 3.31 5.0–11.0 RBC (91012/L) 2.79 2.74 2.26 2.57 2.63 3.26 3.60 3.52 2.97 2.54 2.80 1.02 7.0–11.0 Haemoglobin 64 62 50 57 59 72 81 79 67 57 64 24 115–160 (gm/L) Haematocrit 17.4 16.9 14.5 16.7 17.3 20.3 22.5 22.4 19.4 16.7 18.3 7.3 34–45 (%) MCV (ﬂ) 62.4 61.8 64.1 65.1 65.7 62.4 62.5 63.7 65.4 65.8 65.5 71.1 36–49 MCH (pg) 23.0 22.5 22.2 22.4 22.3 22.2 22.3 22.4 22.5 22.4 22.9 23.4 12.7–17.5 MCHC 369 364 347 344 339 355 357 351 344 340 350 330 340–360 (gm/L) Platelet 12106211114131520293128 13–30 (9109/L) Neutrophil 1.16 1.55 2.30 2.25 2.42 2.01 2.43 3.65 2.86 2.02 2.21 2.25 2.1–6.7 (9109/L) Band 0 0 0 0 0 0 0 0 0.1504 0.1806 0 0 0–0.2 Neutrophil (9109/L) Lymphocyte 1.0 0.81 0.55 0.59 0.57 0.32 0.52 0.70 0.60 0.57 0.67 1.03 1.3–4.5 (9109/L) Monocyte 0.16 0.07 0.03 0.25 0.19 0.12 0.29 0.04 0.15 0.21 0.15 0.03 0–0.5 (9109/L) Eosinophil 000000000 0.300 0–0.5 (9109/L) Basophil 000000000 0 00 0–0.2 (9109/L) Plasma 106 102 92 90 93 84 87 85 84 78 84 68 60–82 Protein (g/L) Fibrinogen 2.0 1.0 2.0 3.0 4.0 2.0 3.0 2.0 3.0 2.0 1.0 3.0 1.0–4.0 (g/L) Triglycerides 37.4 31.5 20.7 17.5 15.9 5.9 6.0 6.1 11.2 16.0 10.9 13.6 0–1.13 (mmol/L)

Bold values are outside of reference range. which was followed by a cross-matched blood transfusion of improvement in the haemogram was noted, pergolide 2 L of whole blood. Unfortunately, the bone marrow aspirate (0.00357 mg/kg bwt, q. 24 h per os) was re-initiated on Day provided inconclusive results. 22. Over the next 2 weeks of hospitalisation, the horse In an effort to rule out immune-mediated thrombo- remained stable with the heart rate fluctuating between a cytopenia, a platelet surface-associated immunoglobulin normal range (48 beats/min) and tachycardia (90 beats/ assay (PSAIg) was submitted; the proportion of the Miniature min). On Day 36, acute signs of colic were observed along horse’s platelets positive for platelet surface-associated with tachycardia (120 beats/min), tachypnoea (72 breaths/ IgG, IgM and IgA was 2, 2 and 2% (reference range <4%), min) and severe anaemia (7%; Table 1). Due to the respectively, indicated that immune-mediated thrombo- deterioration of condition, the horse was subjected to cytopenia was unlikely. Additional diagnostic tests included euthanasia. qPCR for detection of Anaplasma phagocytophilum and ELISA for Equine Infectious Anaemia Virus; these tests were Post-mortem examination negative. On necropsy examination, gross examination revealed an 9 9 Treatment and outcome enlarged pituitary gland (2 cm 1.5 cm 1 cm), a pale and friable liver and a markedly enlarged spleen The horse was continued on dexamethasone (0.07 mg/kg (68 cm 9 40 cm 9 9 cm) which was mottled and markedly bwt, q. 24 h i.v.) for 2 more weeks at which point the dose congested (Fig 1). Additional findings at gross examination was tapered and discontinued on Day 21. On Day 8, the included the presence of haemomelasma ilei on the ileum total WBC remained relatively static, but the haematocrit and two 0.2 cm white foci within the liver. The sternebrae, (20.3%) and platelet count (14,000 cells/lL) increased slightly femur, humerus and rib bones were split to evaluate for while the serum triglyceride concentration decreased to myelophthisis. The medullary cavity of the long bones 5.9 mmol/L. A second bone marrow aspirate collected from contained slightly yellow fatty tissue which floated in formalin. the sternum was attempted with cytological findings of The marrow cavity of the ribs and long bones was dark red in haemodilution; these results suggested bone marrow aplasia, colour. Histopathological evaluation of the spleen revealed replacement of normal bone marrow with fibrinous or the red pulp was markedly congested and the white pulp adipose tissue, or a poor quality sample. As minimal was moderately expanded and contained numerous

reported in horses, was the presumptive cause of destruction in multiple cell lineages. The exact cause of the acute and severe drop in red cells noted on Day 36 of hospitalisation is unknown, but might have corresponded with an acute episode of extravascular consumption of red cells within the spleen, loss of transfused red blood cells or hastened disease progression following the end of corticosteroid usage. Hypersplenism refers to a group of syndromes that involve splenomegaly and peripheral cytopenia and may be associated with a variety of causes. Dameshek (1955) proposed four criteria for diagnosis of hypersplenism: 1) splenomegaly; 2) one or more types of cytopenia; 3) normal or hyperplastic bone marrow and 4) disappearance of pathological changes of blood cells after splenectomy. Fig. 1: Gross appearance of the markedly enlarged spleen that The first three criteria were documented in the horse was mottled and congested. presented here, and while splenectomy is possible in the horse, this procedure was not attempted as hypersplenism was not recognised ante mortem (Rigg et al. 1997). macrophages with phagocytised erythrocytes and lesser Current knowledge in regard to the pathophysiology of numbers of phagocytised platelets, leucocytes and brown hypersplenism is incomplete, but existing information suggests granular haemosiderin pigment interpreted as haemosiderin. that haematopoietic cells are sequestered within an enlarged Microscopically, the bone marrow had densely cellular spleen, consequently resulting in cytopenia (anaemia, haematopoietic tissue within the intertrabecular space with neutropenia and/or thrombocytopenia). Compensatory bone adequate numbers of megakaryocyctes. The blast to marrow hyperplasia is also observed (Lv et al. 2016). maturing cell ratio was approximately 2:8, with maturing cells Hypersplenism can generally be classified into either primary of the erythroid lineage being over-represented with marked or secondary hypersplenism. In primary hypersplenism, the erythroid hyperplasia; no evidence of fibrosis or neoplasia underlying cause is uncertain, but is brought on by a was observed within the bone marrow. Within the liver was a disorder within the spleen itself and includes conditions small nodular focus of subcapsular mineralisation surrounded such as primary splenic hyperplasia, primary splenic by a thick band of dense fibrous connective tissue, most likely granulocytopenia, primary splenic pancytopenia and splenic secondary to prior parasite migration. The cytoplasm of anaemia or thrombocytopenia (Lv et al. 2016). In comparison, centrilobular and midzonal hepatocytes was diffusely with secondary hypersplenism an underlying aetiology can distended by clear spaces to eosinophilic flocculent material be documented which might include an infectious disease interpreted as glycogen. Evaluation of the pituitary gland such as hepatitis, brucellosis, infectious mononucleosis or confirmed hyperplasia of the pars intermedia consistent with malaria, or secondary to portal hypertension, granulomatous the clinical diagnosis of PPID. The presence of marked inflammation (e.g. systemic lupus erythematosus), neoplasia splenomegaly combined with phagocytosis of erythrocytes, (e.g. splenic lymphosarcoma, leukaemia) or myeloproliferative platelets and leucocytes, in light of the horse’s clinical disorders (e.g. myeloid leukaemia, myelofibrosis) (Lv et al. cytopenias, was consistent with a diagnosis of hypersplenism. 2016). A large volume of information is available in people in regard to liver disease and portal hypertension as a cause of Discussion hypersplenism; however, portal hypertension is not common in horses (Boyer and Habib 2015). In the case presented here, no The combination of anaemia, thrombocytopenia and evidence of portal hypertension was present indicating that leucopenia is not commonly observed in equine medicine the liver was not involved in the pathogenesis. but possible causes include myelophthisic diseases, immune- The exact pathogenesis by which peripheral cytopenias mediated disorders and infectious diseases such as equine occur in association with hypersplenism is unknown but piroplasmosis and equine granulocytic anaplasmosis (Lavoie several mechanisms have been proposed. Retention of et al. 1987; Ringger et al. 1997; Dziegiel et al. 2013; Wise et al. blood cells within the spleen might play a large role in the 2014). Myelophthisic diseases replace normal bone marrow development of peripheral cytopenias (Lv et al. 2016). Portal architecture with neoplastic, fibrous or inflammatory tissue hypertension can cause the spleen to increase in size with specific myelopthisical diseases reported in horses dramatically and is associated with increased splenic blood including acute myeloid leukaemia, acute lymphocytic volume due to increased venous pressure (Lv et al. 2016). The leukaemia, myeloid fibrosis and bone marrow aplasia (Angel size of the spleen can also increase from increased splenic et al. 1991; Lester et al. 1993; Ringger et al. 1997). arterial blood flow induced by a variety of diseases causing Alternatively, immune-mediated disorders can impact a hyperaemic splenomegaly. Consequently, retention of 5–20 single or multiple cell lineage(s) including platelets, times higher concentrations of leucocytes, erythrocytes and erythrocytes and neutrophils. Immune-mediated destruction platelets can occur within the spleen facilitating capture, of various cell lineages has been reported in horses and can phagocytosis or destruction of blood cells by phagocytes, be primary or secondary to medications, immunodeficiency, thus resulting in peripheral cytopenias (Lv 2014; Lv et al. 2016). malignancy or lymphoproliferative disorders (Brumbaugh In healthy people, approximately 30% of platelets are stored et al. 1982; Thomas and Livesey 1998; McGovern et al. 2011; in the spleen with the remaining platelets within the Teachey and Lambert 2013). The case presented here is circulation. With hypersplenism, 50–90% of platelets are unique in that hypersplenism, which has not been previously retained in the enlarged spleen (Aster 1966). Other possible

mechanisms of peripheral cytopenias include enhanced artery embolisation or total splenectomy (Lv et al. 2016). In macrophage phagocytosis which has been reported to have people, these treatments may be curative. In contrast, significantly increased phagocytosis, cytokine secretion and generalised splenomegaly in dogs is often associated with antigen processing in people with portal hypertension, malignancy of myeloid lineage and disease may become upregulation of cytokines related to monocyte chemotaxis disseminated prior to splenectomy (Spangler and Kass 1999). and macrophage activation (i.e. macrophage colony- However, reports of clinical resolution of anaemia and stimulating factor, tumour-necrosis factor-b, interferon-c and thrombocytopenia following surgical removal of the spleen interleukin-10) and possibly gene dysregulation (Griffith and have been reported in two dogs, one with extramedullary Janney 1990; Lv et al. 2016). haematopoiesis and the other with histologically confirmed Splenomegaly in horses is considered an uncommon cause hypersplenism (Kuehn and Gaunt 1986; Sawasima et al. of primary disease. Splenomegaly was reported as a cause of 1990). Supportive therapy in humans and animals may recurrent colic in a 10-year-old Thoroughbred gelding (Ortved involve transfusion of whole blood, packed red blood cells or et al. 2008). Additional causes of splenomegaly include platelet-rich plasma; however, these are unlikely to result in haematological disorders, splenic artery thrombosis and disease resolution. infectious diseases such as babesiosis, theileriosis and infection In summary, the case presented here highlights with equine infectious anaemia virus (Scott et al. 1978; hypersplenism, an unusual disease process which has not Brumbaugh et al. 1982; Ribeiro et al. 2013; Wise et al. 2014; previously been reported in horses, as a cause of anaemia, Valli et al. 2016). Infiltrative disease such as amyloidosis and thrombocytopenia and leucopenia. Thorough ultrasound neoplasia may cause diffuse or nodular splenomegaly and imaging of the spleen might identify splenomegaly, although include melanoma, lymphoma and haemangiosarcoma (Kim this is difficult to quantify in the horse due to the variable size of et al. 2005). The authors are unaware of a known reference the equine spleen. Alternatively, splenic biopsy or nuclear range for splenic size in Miniature Horses, however; it is scintigraphy might help identify increased sequestration or generally accepted that a subjective comparison of the phagocytosis of various cell lines which would support a spleen to other internal organs and body size is an adequate diagnosis of hypersplenism (Kinuya et al. 2003). Future equine measure of splenomegaly in veterinary patients (Valli et al. cases might benefit from splenectomy as a cure for the various 2016). cytopenias that can be observed in cases of hypersplenism. Additional features of this case included persistent hypertriglyceridaemia despite a good appetite and uncontrolled PPID. Hypertriglyceridaemia has been reported Authors’ declaration of interests secondary to endocrine disorders, including PPID, and is No conflicts of interest have been declared. associated with hyperglycaemia and insulin resistance (Dunkel et al. 2014). It is possible that the use of corticosteroids in a horse with PPID exacerbated glucose and energy dysregulation. In Ethical animal research this case, it was decided that attempting to correct the This is a case report with no IACUC needed. anaemia and thrombocytopenia was more clinically relevant than the moderate increase in tryglycerides. While hepatic lipidosis was a consideration in this case, there was no evidence Source of funding of increased liver enzymes on serum biochemistry profile or fatty None. infiltration on necropsy suggesting that hypertriglyceridaemia did not contribute substantially to the horse’s clinical condition and outcome. The horse in the case here also had persistent Authorship lymphopenia which could be associated with high cortisol R. Ruby and D. Wong contributed to case management and concentrations observed with PPID, a viral or other systemic authorship. B. Sponseller contributed to case management infection, or exogenous corticosteroid therapy. A and M. Yaeger contributed to necropsy. hyperproteinaemia was noted on admission with significant variation between total protein measured between refractometer and biuret method. The variation in values was References primarily attributed to the elevation in triglycerides which may Angel, K.L., Spano, J.S., Schumacher, J. and Kwapien, R.P. (1991) falsely elevate total protein when measured with a Myelophthisic pancytopenia in a pony mare. J. Am. Vet. Med. refractometer (Thomas 2000). Total protein measured by the Assoc. 198, 1039-1042. biuret method was within normal limits on the day of admission Aster, R.H. (1966) Pooling of platelets in the spleen: role in the but decreased by the final day of hospitalisation. This decrease pathogenesis of ‘hyperslenic’ thrombocytopenia. J. Clin. Invest. 45, in total protein appeared to be a combination of a loss of 645-657. albumin and globulins as the fibrinogen remained stable and Boyer, T.D. and Habib, S. (2015) Big spleens and hypersplenism: fixitor the decrease in albumin for 35–27 g/L was not sufficient to forget it? Liver Int. 35, 1492-1498. account for the total decrease (75–57 g/L). The cause of this Brumbaugh, G.W., Stitzel, K.W., Zinkl, J.G. and Feldman, B.F. (1982) decrease in total protein may reflect both a decrease in Myelomonocytic myeloproliferative diseases in a horse. J. Am. Vet. Med. Assoc. 180, 313-316. production of immunoglobulins secondary to lymphopenia, as Dameshek, W. (1955) Hypersplenism. Bull. N. Y. Acad. Med. 31, well as undetected loss of albumin or decreased hepatic 113-116. production of albumin secondary to inflammation. Dunkel, B., Wilford, S.A., Parkinson, N.J., Ward, C., Smith, P., Grahame, Treatment in people with hypersplenism includes L., Brazil, T. and Schott, H.C. (2014) Severe hypertriglyceridaemia in addressing the primary aetiology when possible as well as horses and ponies with endocrine disorders. Equine Vet. J. 46, external irradiation and ablation of the spleen, partial splenic 118-122.

Dziegiel, B., Adaszek, L., Kalinowski, M. and Winiarczyk, S. (2013) Equine Ribeiro, I.B., Camara, A.C.L., Bittencourt, M.V., Marcola, T.G., Paludo, granulocytic anaplasmosis. Res. Vet. Sci. 95, 316-320. G.R. and Soto-Blanco, B. (2013) Detection of Theileria equi in Grifﬁth, R.C. and Janney, C.G. (1990) Hematopoetic system: bone marrow spleen and blood of asymptomatic piroplasm carrier horses. Acta Parasitol. 58, 218-222. and blood, spleen, and lymph nodes. In: Anderson’sPathology, 9th edn., Ed: J.M. Kissane, Mosby, St. Louis, MO. pp 1408-1447. Rigg, D.L., Reinertson, E.L. and Buttrick, M.L. (1997) A technique for elective splenectomy of equidae using transthoracic approach. Kim, D.Y., Taylor, H.W., Eades, S.C. and Cho, D.Y. (2005) Systemic AL amyloidosis associated with multiple myeloma in a horse. Vet. Vet. Surg. 16, 389-391. Path. 42, 81-84. Ringger, N.C., Edens, L., Bain, P., Raskin, R.E. and Larock, R. (1997) Acute myelogenous leukaemia in a mare. Aust. Vet. J. 75, 329-331. Kinuya, K., Matano, S., Nakashima, H. and Take, S. (2003) Scintigraphic prediction of therapeutic outcomes of splenectomy in patients Sawasima, K., Shitaka, H., Sawasima, Y. and Maede, Y. (1990) Primary with thrombocytopenia. Ann. Nucl. Med. 17, 161-164. hypersplenism in a dog. J. Jap. Vet. Med. Assoc. 43, 203-206. Kuehn, N.F. and Gaunt, S.D. (1986) Hypocellular marrow and Scott, E.A., Trapp, A.L., Derksen, F.J. and Thompson, R.A. (1978) extramedullary hematopoiesis in a dog: hematologic recovery Splenomegaly and splenic infarction in a Standardbred colt. Vet. after splenectomy. J. Am. Vet. Med. Assoc. 188, 1313-1315. Med Small Anim. Clin. 73, 1549-1556. Lavoie, J.P., Morris, D.D., Zinkl, J.G., Lloyd, K. and Divers, T.J. (1987) Spangler, W.L. and Kass, P.H. (1999) Splenic myeloid metaplasia, Pancytopenia caused by bone marrow aplasia in a horse. J. Am. histiocytosis, and hypersplenism in the dog (65 cases). Vet. Path. Vet. Med. Assoc. 191, 1462-1464. 36, 583-593. Lester, G.D., Alleman, A.R., Raskin, R.E. and Meyder, J.C. (1993) Teachey, D.T. and Lambert, M.P. (2013) Diagnosis and management Pancytopenia secondary to lymphoid leukemia in three horses. J. of autoimmune cytopenias in childhood. Pediatr. Clin. North Am. Vet. Intern. Med. 7, 360-363. 60, 1489-1511. Lv, Y. (2014) Causes of peripheral blood cytopenias in patients with Thomas, J.S. (2000) Overview of plasma proteins. In: Schalm’s liver cirrhosis portal hypertension and clinical signiﬁcances. Open J. Veterinary Hematology, 5th edn., Eds: B.F. Feldman, J.G. Zinkl and Endocr. Metab. Dis. 4, 2014. N.C. Jain. Lippincott Williams & Wilkins, Philadelphia. pp 891-898. Lv, Y., Lau, W.Y., Li, Y., Deng, J., Han, X., Gong, X., Liu, N. and Wu, H. Thomas, H.L. and Livesey, M.A. (1998) Immune-mediated hemolytic (2016) Hypersplenism: history and current status. Exp. Ther. Med. 12, anemia associated with trimethoprim-sulphamethoxazole 2377-2382. administration in a horse. Can. Vet. J. 39, 171-173. McGovern, K.F., Lascola, K.M., Davis, E., Fredrickson, R.L. and Tan, R. Valli, V.E.O., Kiupel, M. and Bienzle, D. (2016) Spleen and (2011) T-cell lymphoma with immune-mediated anemia and hemolymphnodes. In: Jubb, Kennedy, and Palmer’s Pathology of thrombocytopenia in a horse. J. Vet. Intern. Med. 24, 1181-1185. Domestic Animals. 6th edn., Ed: M.G. Maxie, Mosby, St. Louis. pp 158-195. Ortved, K.F., Witte, S., Fleming, K., Nash, J., Woolums, A.R. and Peroni, J.F. (2008) Laparoscopic-assisted splenectomy in a horse with Wise, N.L., Pelzel-McCluskey, A.M., Mealey, R.H. and Knowles, D.P. splenomegaly. Equine Vet. Educ. 20, 357-361. (2014) Equine piroplasmosis. Vet. Clin. Equine 30, 677-693.

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Clinical Commentary Hypersplenism E. Davis VMTH–Clinical Sciences, Kansas State University, Manhattan, USA Corresponding author email: [email protected]

Keywords: horse; hypersplenism; pancytopenia; colic

The current report by Ruby et al. (2019) characterises a marrow ante mortem. Hepatic findings were not indicative of geriatric equine patient with nonspecific clinical signs that a primary hepatic disorder, consisting of previous parasitic included reduced appetite and intermittent colic. These signs migration and glycogen accumulation. The definitive were associated with marked haematological abnormalities diagnosis was established based on the post-mortem findings. that included leukopenia, neutropenia, anaemia and In an alternate scenario where hypersplenism is suspected thrombocytopenia. Clinical signs of hypertrichosis and-or ante mortem, diagnosis may be considered based on hyperhidrosis were not evident but subsequent evaluation of haematological change, evidence of splenic enlargement, plasma insulin and ACTH concentrations supported the histopathological assessment of splenic tissue and ruling out diagnosis of PPID. Although immune-mediated disease was other causes for pancytopenia such as bone marrow considered as a possible cause for pancytopenia along with analysis. differential considerations that included myelophthisis, Although the diagnosis of hypersplenism has not been neoplasia and equine infectious anaemia virus infection, made previously in the equine literature, the current report these were effectively ruled out. Ultimately despite the provides valuable information for the equine clinician to provision of appropriate symptomatic therapy and apparent consider while maintaining this differential possibility in a improved condition, marked anaemia and disease patient that demonstrates appropriate clinical and progression resulted in euthanasia. Post-mortem examination haematological findings. When considering the diagnosis of revealed that clinical findings were associated with the hypersplenism, the clinician needs to consider the potential primary disorder of hypersplenism. for anatomic abnormalities that may suggest this differential Although uncommon, splenic disease occurs in horses, possibility. Specifically, recognising that equine splenic with the most common primary condition involving anatomy is relatively constant, with a consistent location in metastatic lymphoma (Rebhun and Bertone 1984). Additional the mid-dorsal portion of the peritoneal cavity. Physiological conditions may include neoplastic disorders such as factors that may impact splenic positioning resulting in haemangiosarcoma (Southwood et al. 2000) or infectious altered location under various conditions include: gastric fill, disease. Infectious diseases may include piroplasmosis intestinal distention, intestinal positioning (or malposition) and (babesiosis) (Zaugg 2009), Equine infectious anaemia virus the presence of primary splenic pathology (Wilson and infection (Sponseller 2009) or Anaplasma phagocytophilum Blikslager 2012). Peripheral and laterally located portions of infection (Adaszek and Winiarczyk 2011). Diagnostic the spleen are slightly convex and are located immediately confirmation of primary splenic disease requires complete adjacent to the diaphragm. More medial (visceral) portions evaluation to rule out other disorders that may secondarily of the spleen are concave, including a longitudinal ridge or result in splenic disease and subsequent splenic hilus that encompasses splenic vessels and nerves. The histopathological examination. Infectious disease involving portion of the organ that lies cranial to the hilus is adjacent to the spleen may be ruled out through serologic or molecular the greater curvature of the stomach, while the portion of techniques. In the current report marked cytopenia was the organ caudal to the ridge is larger and generally sits investigated through testing for immune-mediated disease to adjacent to the descending colon, the left portion of the determine the presence of platelet surface associated ascending colon and the small intestine. The splenic base is immunoglobulin (Davis et al. 2002), Coombs testing, equine located between the left crus of the diaphragm, sublumbar infectious anaemia ELISA testing and ruling out Anaplasma muscles dorsally, whereas medially the spleen sits near the phagocytophilum through polymerase chain reaction (PCR) pancreas and left kidney. External landmarks typically include testing. Definitive diagnosis in this report was based on the last three to four ribs and often extend approximately 2 necropsy examination that revealed a markedly enlarged to 3 cm into the paralumbar fossa. The only region that is spleen that appeared mottled and congested. Upon consistently palpable is the caudodorsal angle, which can be histopathological examination red pulp of the spleen was examined upon rectal palpation (when possible and markedly congested while white pulp was moderately appropriate). The ventral most portion of the spleen is small expanded, containing numerous macrophages with and usually found in the region of the 9th, 10th or 11th rib, phagocytised erythrocytes and fewer engulfed platelets sitting just proximal to the costal arch. The location of the leukocytes and haemosiderin appearing pigment (product of spleen is maintained within the peritoneal cavity with the erythrophagocytosis). Microscopic examination confirmed phrenicosplenic and nephrosplenic ligaments (Wilson and erythroid hyperplasia as an appropriate response to marked Blikslager 2012). Gastric attachment involves the gastrosplenic anaemia. Lack of evidence of marrow fibrosis or neoplasia ligament, which extends beyond this location as the ruled out primary bone marrow dysfunction, consistent with superficial component of the greater omentum. Anatomic previous bone marrow diagnostic testing that failed to evaluation of the spleen in the equine patient is relatively definitively demonstrate primary pathology of patient bone straightforward and can be achieved through a left

abdominal approach, extending from the approximately 8th immune-mediated disorders, infectious disease, neoplasia or or 9th intercostal space to examine the cranial pole to the myelophthisis (Ruby et al. 2019). In human medicine, 17th intercostal space in the region of the paralumbar space conditions involving cytopenia may involve primary or to examine the caudal pole (Reef 1998). Dorsal splenic secondary hypersplenism. Additionally, a recent retrospective margins are located adjacent to the left kidney. The spleen report characterised the exclusive nature of hypersplenism as may cross the ventral abdomen and can be partially the only cause of cell removal in affected human patients observed to the right side of midline in some horses. (Lv et al. 2017). In this recent report, among 183 patients with Ultrasonographic imaging with a 3.5–5 mHz probe provides hypersplenism, diagnosis was confirmed with histopathology the clinician with an ability to fully examine organ margins and was evidenced by splenic enlargement. Imaging to and parenchymal structure. Examination of the normal spleen define splenic size included confirmation with ultrasound and will reveal a relatively homogeneous and echogenic organ in computed tomography imaging. Surgical splenectomy was healthy, adult horses. The spleen contains a hyperechoic performed for various reasons that included severe capsule, while the parenchyma is echogenic and appears gastrointestinal haemorrhage 97 (53%), marked thrombo- finely mottled in appearance. Splenic dimensions are cytopenia in 55 (30%) and primary splenomegaly 31 (16.9%). variable, with the caudal pole generally measuring 5–8 cm, Peripheral cytopenia was identified in 72.2% of the patients which terminates in a tapered caudal pole with a thin with hypersplenism. Overall among patients with marked terminal edge (Reef 1998). In the adult horse the spleen is cytopenia, this finding was a direct result of hypersplenism in approximately 50 cm in length and approximately 20–25 cm approximately 80% of the patients, 16% were a result of in width (Wilson and Blikslager 2012). The current report hypersplenism with other factors and approximately 3.5% of involving a miniature horse demonstrates an added the cytopenia cases were due to other factors entirely (Lv challenge due to a lack of measurements for a horse with et al. 2016). In cases where hypersplenism is the primary small stature (Ruby et al. 2019). In this instance, the use of cause of cytopenia the expectation is that cell counts will landmarks should provide the clinician with an ability to return to normal following splenectomy. Hypersplenism is determine approximate size and location of the organ. therefore correlated with spleen size and phagocytic In a previous report of splenomegaly, recurrent colic was capacity of splenic macrophages. The larger the size of the the predominant clinical finding, in this patient the spleen spleen, the greater the cell storage capacity and therefore was observed to be markedly enlarged, evidenced by phagocytic capacity leading to a more significant reduction presence along the entire length of the left abdominal wall in circulating cell count(s) and more substantial change in cranially to the left elbow and caudally to the inguinal cell populations that should be expected post-operatively, region. Similarly, on the right side of the patient the spleen supporting the suggestion that in similar cases surgical was observed to extend from the 8th intercostal space to the splenectomy may be curative. Although well described in the lower flank region. In this patient the ultrasonographic surgical veterinary literature, among equine surgical appearance of the splenic parenchyma was considered procedures, splenectomy is recognised to be a technically normal (Ortved et al. 2008). It should be emphasised that the challenging procedure due to the cranial location of the presence of splenic enlargement alone does not establish organ within the peritoneal cavity, substantial ligamentous the diagnosis of hypersplenism, however the development of attachments and complex innervation and extensive splenomegaly alone may lead to clinical signs of abdominal vascularisation. Additionally, previous reports have supported pain and associated presentation for colic. the suggestion that laparoscopic removal may provide Overall, hypersplenism is an uncommon condition among surgeons with improved visualisation of the medial aspect of veterinary patients and one that has not been previously the organ providing an improved ability toward vessel reported in the equine literature. Hypersplenism is classified as transection and ligation and has been reported in an equine either primary or secondary. Primary hypersplenism is patient with marked splenomegaly and colic (Ortved et al. associated with splenomegaly and associated haematological 2008). Regardless, in patients that present with splenomegaly abnormalities without any other primary cause (Carere and and hypersplenism, surgical splenectomy may provide a Clemes 1962). Primary hypersplenism may be developmental or therapeutic option. congenital resulting in primary haemolytic anaemia, primary or Information provided in the current report suggests that idiopathic thrombocytopenic (purpura, term used in human when confronted with an equine patient with suspected literature), primary splenic neutropenia or any combination in primary hypersplenism, differential consideration should addition to the syndrome of primary pancytopenia (Wintrobe include this as a primary disorder (Ruby et al. 2019). Although 1983). Secondary hypersplenism is associated with the the specific mechanism of cellular destruction and removal is reduction in any individual cell line resulting from splenic incompletely understood, there is evidence to demonstrate removal of blood products, which results from splenic that similar to humans, horses may suffer from consequences enlargement as a consequence of another disease processes of hypersplenism in a similar manner leading to marked and (Carere and Clemes 1962; Lv et al. 2016). Enlargement may clinically profound cytopenia. Clinical history of colic signs occur secondary to venous occlusion leading to chronic combined with haematological evidence of marked congestive splenomegaly or the spleen may be directly cytopenia should increase the index of suspicion for this as a involved in the disease process. Chronic congestive possible aetiological cause. Additional diagnostic evidence splenomegaly may occur secondary to chronic fibrotic hepatic to support this working diagnosis including abdominal disease, portal vein thrombosis, splenic vein obstruction or ultrasonographic evaluation will help to further increase the thrombosis, aneurism of the splenic artery or due to cysts, fibrosis likelihood of hypersplenism as a primary cause for cellular or neoplasia involving the pancreas (Lv et al. 2016). destruction. Although the patient in the current report did not Peripheral cytopenia may result from a variety of factors, have definitive evidence of splenomegaly that was evident as described in the current report, which may involve on abdominal ultrasound, there was only an individual

ultrasound performed. It is possible that the ultrasound Source of funding performed at presentation may not have revealed an obviously enlarged spleen as the presenting problem was None. colic in a miniature horse and the focus of examination may have been on gastrointestinal structures. Without specific References clinical suspicion of splenic disease diagnostic confirmation of Adaszek, L. and Winiarczyk, S. (2011) Identification of Anaplasma spp. this abnormality may not have been immediately evident, rickettsia isolated from horses from clinical disease cases in Poland. particularly if the patient was overweight that may have Zoonoses Public Health 58, 514-518. reduced diagnostic ultrasonic acuity due to poor visceral Carere, R.P. and Clemes, I.L. (1962) An unusual cause of detail. Repeated ultrasound image examinations may have splenomegaly and pancytopenia (Secondary hypersplenism). provided enhanced diagnostic criteria of splenomegaly. Can. Med. Assoc. J. 86, 833-835. Based on the findings of this report, suspect cases should be Davis, E.G., Wilkerson, M.J. and Rush, B.R. (2002) Flow cytometry: carefully examined for the potential finding of splenomegaly, clinical applications in equine medicine. J. Vet. Intern. Med. 16, with careful attention to organ location and specific 404-410. association with localised organs and borders. Similar to the Lv, Y., Lau, W.Y., Li, Y., Deng, J., Han, X., Gong, X., Liu, N. and Wu, H. (2016) Hypersplenism: history and current status. Exp. Ther. Med. 12, reported case additional diagnostic testing should also 2377-2382. include abdominocentesis to rule out other primary Lv, Y., Yee, L.W., Wu, H., Han, X., Gong, X., Liu, N., Yue, J., Li, Q., Li, Y. peritoneal disease as well as bone marrow biopsy and and Deng, J. (2017) Causes of peripheral cytopenia in hepatitic aspirate to investigate the marrow microenvironment. cirrhosis and portal hypertensive splenomegaly. Exp. Biol. Med. Collectively the findings of (1) abdominal pain and colic, (2) (Maywood) 242, 744-749. haematological abnormalities that include marked and Ortved, K.F., Witte, S.H. and Fleming, K. (2008) Laparoscopic assisted persistent pancytopenia, (3) ultrasonographic evidence of splenectomy in a horse with splenomegaly. Equine Vet. Educ. 20, marked splenomegaly and (4) splenic histopathological 357-361. examination that reveals splenic engorgement and cellular Rebhun, W.C. and Bertone, A. (1984) Equine lymphosarcoma. J. Am. phagocytosis will help to support the diagnosis of Vet. Med. Assoc. 184, 720-721. hypersplenism in the equine patient. Therapeutic implications Reef, V.B. (1998) Adult abdominal ultrasound. In: Equine Diagnostic from this diagnosis are substantial. When diagnostic criteria Ultrasound, Ed: V.B. Reef, W.B. Saunders, Philadelphia. pp 273-362. are made in the appropriate clinical setting, splenectomy Ruby, R.E., Wong, D.M., Sponseller, B.A. and Yaeger, M. (2019) Suspected case of hypersplemism as a cause of anaemia, may be considered and when successfully performed may thrombocytopenia and leucopenia in a Miniature Horse gelding. provide therapeutic resolution leading to patient survival. The Equine Vet. Educ. 31, 530-534. current report provides compelling evidence of a somewhat Southwood, L.L., Schott, H.C., Henry, C.J., Kennedy, F.A., Hines, M.T., unique disease disorder that has not been previously Geor, R.J. and Hassel, D.M. (2000) Disseminated reported in the equine literature. Thorough diagnostic hemangiosarcoma in the horse: 35 cases. J. Vet. Intern. Med. 14, evaluation with skilled surgical intervention may provide a 105-109. potentially favourable outcome in cases equine Sponseller, B.A. (2009) Diseases of the hematopoietic and hypersplenism. hemolymphatic systems. In: Large Animal Internal Medicine, Ed: B.P. Smith, Mosby, St. Louis. pp 1162-1163. Wilson, W.D. and Blikslager, A.T. (2012) Stomach and spleen. In: Equine Author’s declaration of interests Surgery, Ed: J. Auer and J. Stick, Elsevier Saunders, St. Louis. pp 388- 402. No conflicts of interests have been declared. Wintrobe, M.M. (1983) Perspective in hematology. Pharos Alpha Omega Alpha Honor Med. Soc. 46, 7-12. Ethical animal research Zaugg, J.L. (2009) Babesiosis. In: Large Animal Internal Medicine, Ed: B.P. Smith, Mosby, St. Louis. pp 1157-1161. Not applicable.

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Case Report Successful surgical debridement of a cerebral Streptococcus equi equi abscess by parietal bone ﬂap craniotomy in a 2-month-old Warmblood foal B. Broux†‡ , T. van Bergen‡§* , S. Schauvliege§, Y. Vali–, L. Lefere † and I. Gielenk †Department of Large Animal Internal Medicine, Ghent University, Merelbeke, Belgium; ‡Clinique Equine d’Acy- Romance, Acy-Romance, France; §Department of Surgery and Anaesthesiology, Ghent University; –Department of Radiology and Surgery, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran; and kDepartment of Medical Imaging and Small Animal Orthopaedics, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium *Corresponding author email: [email protected]

Keywords: horse; brain surgery; strangles; equine medicine

Summary Brain abscesses and intracranial masses have been regularly described in horses. While these conditions can sometimes be treated medically, other horses develop large abscesses or haematomas, requiring surgical treatment. Historically, surgical treatment possibilities were limited and mortality rates high. This case report describes a novel surgical approach for the intracranial debridement of a large Streptococcus equi equi abscess in a young Warmblood foal. A 2-month-old female Warmblood foal was presented with severe neurological signs of acute onset. Computed tomography (CT) revealed a 3 9 4 9 4 cm cerebral mass in the left brain hemisphere with soft-tissue/cellular fluid density and a hyperdense wall, as well as cerebral oedema. Craniotomy, using a parietal bone flap technique, allowed the abscess to be sampled, drained and Fig 2: Surgical access to the abscess in the left hemisphere lavaged (Fig 1). Immediately post surgery the foal showed through a parietal bone flap technique with the foal in sternal significant clinical improvement (Fig 2). Sample culture recumbency. Both sides of the meningeal incision were pulled laterally with a monofilament USP 2/0 (Poliglecaprone, Monocryl, confirmed Streptococcus equi equi infection. The foal was Ethicon) stay suture to expose the underlying abscess cavity. further medically treated for 6 weeks, leading to complete Rostral to the left and caudal to the right. clinical and radiographical recovery at 6 and 9 months follow- up. Intracranial surgery in equine medicine is limited. Bone flap techniques have been traditionally used to access sinus cavities but this report proves it to be useful for intracranial procedures requiring exposure of the cerebrum. The use of a parietal bone flap craniotomy, instead of a partial craniectomy, may have reduced the risk of infection post-operatively and led to a better cosmetic outcome. Using a parietal bone flap to gain access to the cerebrum should be considered for the treatment of cerebral masses in the horse.

Key points Surgical treatment possibilities for intracranial masses or brain abscesses are limited and mortality rates are high. This case report describes a novel surgical approach, using a parietal bone flap technique, for the Fig 1: Pre-operative transverse CT-images after i.v. contrast intracranial debridement of a large Streptococcus administration of the cerebrum at the level of the temporal lobe. equi equi abscess in a young Warmblood foal. 3 3 fl A4 3 4 cm mass with soft-tissue/cellular uid density with Using a parietal bone flap instead of partial hyperdense wall and significant post-contrast rim enhancement is craniectomy to gain access to the cerebrum is a less visible in the left brain hemisphere. A large amount of associated invasive procedure leading to a better aesthetic result mass effect is present (black arrow). and should be considered for the treatment of cerebral masses in the horse.

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Clinical Commentary Metastatic abscessation and other potential complications following strangles F. M. Whitlock, J. R. Newton and A. S. Waller Animal Health Trust, Newmarket, UK Corresponding author email: fl[email protected] Animal Health Trust recorded variable extents to which S. equi infection persisted after signs resolved, with higher Introduction rates where more intensive outbreak investigation was conducted and longer periods of carriage where animals The earliest documented report of strangles was made over were left untreated (Newton et al. 1997, 1999, 2000). The 750 years ago by a knight of the King of Naples (Rufus 1251), bacteria gain entry to the guttural pouches through rupture although Streptococcus equi was not identified as the of retropharyngeal lymph node abscesses, anatomically infectious causative agent until 1888 (Schutz€ 1888). The DNA adjacent to the pouches. Carriage is thought to develop as sequence of the S. equi genome was completed in 2009, a result of incomplete drainage of material from the providing a step change in our knowledge of this bacterium pouches, with chondroids forming as purulent material dries. (Holden et al. 2009). Developments in modern diagnostics Carrier status is still possible even if endoscopic visualisation of enable rapid and accurate detection of clinical cases and the pouches reveals no gross abnormalities as the bacteria screening for subclinically infected carriers (Robinson et al. can produce a microscopic biofilm (Steward et al. 2017). A 2013; Webb et al. 2013) to ensure optimum approaches to guttural pouch lavage tested using sensitive qPCR (Webb outbreak investigations and control. Now, novel research is et al. 2013) is required to identify these carriers. utilising genome sequencing to identify the geographical Treatment of most strangles cases predominantly involves distribution of strains and epidemiological links between supportive care, with the majority of cases resolving naturally outbreaks (Harris et al. 2015). Such advancements improve with time. Systemic antibiotic treatment of classical cases knowledge of the bacteria and its spread and facilitate remains contentious among veterinary surgeons and is enhanced targeted prevention to reduce the high welfare currently largely discouraged in cases without severe and economic costs arising from the disease. complications. Antibiotics may actually prolong the period over which clinical signs occur by increasing the risk of re- Clinical presentation emergence of clinical signs after earlier clinical improvement and ultimately resulting in a poorer immune response (Boyle The ‘classical’ clinical presentation of strangles involves an et al. 2018). Antibiotics may be indicated, however, if horses apparent upper respiratory tract infection, with signs that are persistently anorexic, pyrexic, profoundly sick with the include mucopurulent nasal discharge (usually bilateral), in disease or immunosuppressed. Endoscopic lavage of the combination with fever, lymphadenopathy and abscessation of guttural pouches is advised, at least 4 weeks after the the submandibular (Fig 1) parotid and retropharyngeal lymph resolution of clinical signs in recovering cases, to rule out nodes (Boyle et al. 2018). On occasion, lymph node carrier status. If carriage in the guttural pouches is confirmed, abscessation can result in upper respiratory tract obstruction, treatment will usually be required and will depend on the the origin for the name of the disease. Strangles is endemic in extent of pathology found in the pouches and may vary if many horse populations and cases will present with varying there is persistence of carriage despite treatment. Resolution severities due to the high chance of previous exposure. Atypical may require a combination of treatments of the guttural strangles, a milder version characterised by a transient fever pouch including; lavage, repeat lavage, local instillation of and minimal nasal discharge may easily be overlooked as antibiotics, indwelling catheters, endoscopic or surgical strangles and result in continued shedding into the environment removal of chondroids (Fig 2) and systemic antibiotics and a source of infection for in-contact horses (Prescott et al. (Newton et al. 1999; Verheyen et al. 2000; Boyle et al. 2018). 1982). Strangles morbidity may be high but mortality from the Treatment is successful in the vast majority of cases, with this disease usually is low, despite the sizeable abscesses formed. being confirmed by qPCR of guttural pouch lavage samples Although highly contagious, S. equi only survives in the taken 2 weeks later. environment for a relatively short period (Weese et al. 2009; Durham et al. 2018) and relies on being transmitted through nasal secretions and contaminated fomites, with shedding Secondary complications occurring 2 to 3 days after onset of pyrexia (Boyle et al. 2018). Purpura haemorrhagica, an aseptic necrotising vasculitis is Carriage of S. equi in recovered animals with no thought to be caused by an immune-mediated type III apparent clinical signs may also be a common reservoir of hypersensitivity (Boyle et al. 2018). Clinical signs include infection (Newton et al. 1997, 1999, 2000). Most cases clear petechiation and/or ecchymoses of mucous membranes the infection within 4 to 6 weeks, but in some animals a and oedema of the head, body or limbs (Fig 3). Treatment carrier state develops and subclinically infected carriers will includes corticosteroids and antibiotics, with a poor prognosis intermittently shed S. equi for a prolonged period beyond reported (Pusterla et al. 2003). resolution of clinical signs (Newton et al. 1997, 1999, 2000; Myopathies can occur secondary to S. equi infection and Verheyen et al. 2000). Previous outbreak investigations by the three different presentations have been reported; muscle

Fig 3: Purpura haemorrhagica petechiation.

Fig 1: Classical disease presentation in a horse with strangles. the bacterial infection (Sponseller et al. 2005). Rhabdomyolysis with progressive atrophy has been predominantly identified in Quarter Horses with and without a predisposition of a concurrent infarctions, rhabdomyolysis with acute myonecrosis and storage myopathy. As for purpura, this condition is believed to rhabdomyolysis with progressive atrophy. Muscle infarctions are be immune mediated and is treated with corticosteroids and thought to be a manifestation of purpura haemorrhagica, with antibiotics (Durward-Akhurst and Valberg 2018). approach to treatment and resultant prognosis being the same Another complication is metastatic abscessation which is (Kaese et al. 2005). Rhabdomyolysis with acute myonecrosis often referred to as ‘bastard’ strangles and was first reported presents with a stiff gait, progressing to recumbency. in the 17th century (Slater 2003). Metastases have been Hypothesised causes include toxic shock or toxic effects from documented as occurring at any site and the aetiopathogenesis is not fully understood but is thought to be through either haematogenous spread, lymphatic migration from an abscess or from spread from close proximity to a septic focus. Research has evaluated how S. equi infects the host at a molecular level, with identification of some of the genes responsible for successful adherence and invasion of the upper respiratory tract epithelium and subsequent spread to blood vessels and lymphatics (Lopez- Alvarez et al. 2017). Genes that code for the development of lymph node abscesses, by the bacteria evading phagocytosis through the production of superantigens, have also been characterised (Paillot et al. 2010). Reported metastatic sites of transmission include; brain, sinus, liver, spleen, kidneys, lung (Fig 4) and mesentery (Boyle et al. 2018). There should be suspicions of metastatic spread for any case with a previous history of exposure to S. equi and signs consistent with abscessation including; intermittent pyrexia and haematological laboratory findings of neutrophilia and hyperfibrinogenaemia (Boyle et al. 2018). Additional clinical signs are dependent on the location of the abscess and resultant impairment of associated structures. A range of prevalences have been documented, one report investigating two outbreaks found 28% (7/25) of cases developed metastatic abscessation (Spoormakers et al. 2003). However, other studies have found prevalence Fig 2: Endoscopic removal of a chondroid from the guttural to be as low as 2% (Sweeney et al. 1987; Duffee et al. pouch. 2015). Metastatic spread has been shown to increase the

the successful treatment of the foal with a cerebral abscess by Broux et al. (2019). The affected 2-month-old foal initially presented with laboratory confirmed clinical strangles and retropharyngeal lymph node abscesses were drained by the attending veterinarian. The foal presented with acute neurological signs 3 weeks later. This case demonstrated neutrophilia, increasing suspicions of an infectious process. CT confirmed the presence of a brain lesion and successful surgical treatment of the cerebral abscess resolved clinical signs. Extension of a nearby infectious process has previously been identified as a route for the development of metastatic abscesses and this case demonstrated continued abscessation of a retropharyngeal lymph node, noted during surgery (Spoormakers et al. 2003; Smith et al. 2004). The majority of brain abscesses reported in horses are thought to have been secondary to systemic disease processes but research has identified cases where an infectious process in the head has preceded the development of brain abscesses (Reilly et al. 1994; Smith et al. 2004). Surgical treatment of a lymph node abscess through drainage has previously been suggested as a risk factor in the development of metastatic disease (Spoormakers et al. 2003) and this case had undergone this treatment prior to the development of metastases. Another risk factor for metastatic abscessation in Fig 4: Metastatic abscesses in the lung. this case report was the foal’s young age and immature immune system, which have again been stated as increasing mortality rate associated with strangles to 62% (Ford and the risk of metastatic disease development (Ramey 2007). Lokai 1980). Risk factors for metastatic development have been hypothesised and include; high infectious dose, increased What’s in store in the future? virulence of infectious strain, host response to infection and antimicrobial use (Ramey 2007). Metastasis following There are many unanswered questions regarding strangles antimicrobial administration is hypothesised to occur as a pathogenesis and future studies hope to better understand result of alterations to the bacteria’s protein synthesis the variable clinical presentations of the disease and relate together with the host’s decreased immune response this to the different S. equi strains. The true prevalence of secondary to the antimicrobial treatment. No experimental strangles in the world is unknown; inferences from UK-based studies have confirmed this and the epidemiological research studies and the Equine Quarterly Disease Surveillance Reports findings are speculative and conflicting. One study found put the figure at around 1000 outbreaks a year in the UK antimicrobial treated horses to be at an increased risk of (Ivens et al. 2011). A Horse Trust funded project at the Animal metastases (Ramey 2007). However, other studies Health Trust is seeking to quantify the extent of the disease documenting a high incidence of complications were not through the development of a UK-based surveillance associated with antimicrobial use (Spoormakers et al. 2003). scheme. Data will be collected from laboratories and Additionally, a study that treated over 50% of cases with treating clinicians, with S. equi isolates being evaluated by antimicrobials did not see an increase in the prevalence of whole genome sequencing to enhance understanding of the metastatic disease (Duffee et al. 2015). epidemiological relationships between outbreaks. This will A cranial abscess caused by S. equi has been described provide information on the temporo-spatial distribution of in the accompanying article (Broux et al. 2019). Previous strangles to inform local targeting of initiatives to raise reports include a study describing cerebral abscesses in four awareness about disease occurrence and methods for both horses during two separate outbreaks of strangles, with two responsible outbreak control as well as disease prevention. cases undergoing Magnetic Resonance Imaging (MRI) and Future preventative measures are likely to include a new one of these also undergoing Computed Tomography (CT) recombinant protein vaccine, with the capacity to (Spoormakers et al. 2003). One outbreak experienced two differentiate infected from vaccinated animals (DIVA), a clinical cases developing neurological signs 4 weeks after capability that is particularly useful towards preventing an initial onset of strangles. Both cases from this outbreak had a endemic disease like strangles (Robinson et al. 2018). retropharyngeal lymph node drained around 7 days Correlating genetic information regarding S. equi with preceding the onset of neurological signs. Spread of S. equi host-specific immune responses to the infection will assist in to the brain is by either close proximity to a septic focus via improving the understanding of the pathogeneses of the connecting structures such as cranial nerves or by potential complications associated with strangles, aiding their haematogenous spread (Spoormakers et al. 2003). diagnosis and ultimate prevention. Advances in diagnostic imaging modalities such as CT and MRI have enhanced the diagnosis of brain lesions and aided Author’s declaration of interests treatment approaches, to improve outcomes (Allen et al. 1987; Cornelisse et al. 2001). This has been demonstrated by No conflicts of interest have been declared.

Ethical animal research VIII: Proc. 8th Int. Conf. on Equine Infectious Diseases. R&W Publications, Newmarket. pp 82-87. Not applicable to this clinical commentary. Newton, J.R., Verheyen, K., Talbot, N.C., Timoney, J.F., Wood, J.L., Lakhani, K.H. and Chanter, N. (2000) Control of strangles outbreaks Authorship by isolation of guttural pouch carriers identified using PCR and culture of Streptococcus equi. Equine Vet. J. 32, 515-526. The manuscript was prepared by F. M. Whitlock with Paillot, R., Robinson, C., Steward, K., Wright, N., Jourdan, T., Butcher, N., contributions from J. R. Newton and A. S. Waller. Heather, Z. and Waller, A.S. (2010) Contribution of each of four superantigens to Streptococcus equi-induced mitogenicity, gamma interferon synthesis, and immunity. Infect. Immun. 78, 1728-1739. References Prescott, J.F., Srivastava, S.K., DeGannes, R. and Barnum, D.A. 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Sanders, M., Simmonds, M., Willey, D., Brooks, K., Aanensen, D.M., Spoormakers, T.J., Ensink, J.M., Goehring, L.S., Koeman, J.P., Ter Braake, Spratt, B.G., Jolley, K.A., Maiden, M.C., Kehoe, M., Chanter, N., F., van der Vlugt-Meijer, R.H. and van den Belt, A.J. (2003) Brain Bentley, S.D., Robinson, C., Maskell, D.J., Parkhill, J. and Waller, A.S. abscesses as a metastatic manifestation of strangles: (2009) Genomic evidence for the evolution of Streptococcus equi symptomatology and the use of magnetic resonance imaging as host restriction, increased virulence, and genetic exchange with a diagnostic aid. Equine Vet. J. 35, 146-151. human pathogens. PLoS Pathog. 5, 1-14. Steward, K.F., Robinson, C., Maskell, D.J., Nenci, C. and Waller, A.S. Ivens, P.A.S., Matthews, D., Webb, K., Newton, J.R., Steward, K., Waller, (2017) Investigation of the fim1 putative pilus locus of Streptococcus A.S., Robinson, C. and Slater, J. D. (2011) Molecular characterisation equi subspecies equi. 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Newton, J.R., Wood, J.L.N., Dunn, K.A., DeBrauwere, M.N. and Webb, K., Barker, C., Harrison, T., Heather, Z., Steward, K.F., Robinson, Chanter, N. (1997) Naturally occurring persistent and C., Newton, J.R. and Waller, A.S. (2013) Detection of asymptomatic infection of the guttural pouches of horses with Streptococcus equi subspecies equi using a triplex qPCR assay. Streptococcus equi. Vet. Rec. 140, 84-90. Vet. J. 195, 300-304. Newton, J.R., Wood, J.L.N. and DeBrauwere, M.N. (1999) Detection Weese, J.S., Jarlot, C. and Morley, P.S. (2009) Survival of Streptococcus and treatment of asymptomatic carriers of Streptococcus equi equi on surfaces in an outdoor environment. Canadian Vet. J. 50, following strangles outbreaks in the UK. Equine Infectious Diseases 968-970.

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The International Society of Equine Locomotor Pathology - 501(c)3 Organization 2716 Landmark School Road The Plains, Virginia 20198 USA www.iselp.org [email protected] Jean-Marie Denoix, President * Kent Allen, Vice President & Executive Director EQUINE VETERINARY EDUCATION 543 Equine vet. Educ. (2019) 31 (10) 543-550 doi: 10.1111/eve.12863

Original Article Comparison between radiography and computed tomography for diagnosis of equine skull fractures C. P. Crijns†* , R. Weller‡, L. Vlaminck§, F. Verschooten¶, S. Schauvliege§, S. E. Powell**, H. J. J. van Bree¶ and I. M. V. L. Gielen¶ †DAP Bodegraven BV, Bodegraven, The Netherlands; ‡Veterinary Clinical Sciences, Royal Veterinary College, Hatﬁeld, Hertfordshire, UK; §Department of Surgery and Anaesthesia of Domestic Animals, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium; ¶Department of Veterinary Medical Imaging and Small Animal Orthopaedics, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium; and **RDC, Rossdale and Partners, Newmarket, Suffolk, UK. *Corresponding author email: [email protected]

Keywords: horse; radiography; computed tomography; head; skull; fracture

Summary investigation modality to visualise bony trauma. However, The equine head is a complex structure prone to traumatic superimposition of the complex bony structures is a major injuries. To determine the value and limitations of radiography disadvantage and limits a complete evaluation of the and (CT) for the diagnosis of skull fracture, the differences potentially affected areas (Tremaine 2004; Beard 2009; between the two modalities were described. Two observers Beccati et al. 2011; Auer 2012). With complex, unstable and/ retrospectively reviewed the radiographic and CT images of or displaced skull fractures (Beccati et al. 2011), more 18 horses with a skull fracture. To allow direct comparison sophisticated cross-sectional imaging modalities, such as between the two modalities, a simplified fracture computed tomography (CT), have been suggested for classification system was used. In 3/18 cases the evaluation diagnostic purposes, as in human medicine (Chacon et al. of the radiographic examination concluded no injuries visible. 2003; dos Santos et al. 2004; Marinaro et al. 2007), allowing In 2/15 cases soft tissue involvement was not detected and in greater recognition of normal anatomy and pathology. 7/15 cases the extension of the fracture was underestimated To our knowledge, no studies comparing the diagnostic with radiography. Radiography classified 4/10 multiple value of different imaging modalities for the evaluation of fractures incorrectly as single fracture and 5/15 comminuted skull fractures in horses have been published, although they fractures on CT were diagnosed as simple fracture with have been published in small animal and human medicine radiography. The number of fragments was underestimated (Creasman et al. 1992; Marinaro et al. 2007; Bar-Am et al. with radiography in 14/15 cases. In conclusion, radiography is 2008). able to diagnose a skull fracture in most cases. Skull fractures The objective of this study was to compare bony fractures however are not similarly classified after radiographic and CT of the horse’s skull using radiography and CT and to provide evaluation, which causes a difference in interpretation and insight into the value and limitations of radiography and CT perception of the fractures. Therefore, CT should be the for the diagnosis of skull fracture. The hypothesis was that modality of choice for surgical planning and prognosis. radiography would be able to detect a skull fracture, but CT would provide more detailed information about the fracture configuration, extent, comminution and involvement of Introduction surrounding structure in horses. The equine head is a complex structure, with a skull that surrounds and protects the brain, sensory organs and upper Materials and methods airway tracts. Traumatic injury to the head is relatively common in horses (Ramirez et al. 1998; Gardelle et al. 1999; All horses that underwent a radiographic and computed Henninger et al. 1999; Tremaine 2004; Lischer et al. 2005; tomographic evaluation resulting in a diagnosis of a skull Wollanke et al. 2006; Schaaf et al. 2008; Furst€ et al. 2010; fracture at the Department of Medical Imaging and Small Beccati et al. 2011; Auer 2012; Caldwell and Davis 2012). The Animal Orthopaedics of the Faculty of Veterinary Medicine of most frequently described causes are blunt trauma and injury Ghent University, Belgium and the private clinic, Rossdales from collision, entrapment of the rostral part of the mandible, Equine Hospital & Diagnostic Centre, UK, between 2009 and and falling over backwards (Ramirez et al. 1998; Henninger 2015 were included in the study. The radiographic and et al. 1999; Beccati et al. 2011; Auer 2012; Caldwell and computed tomographic examinations were retrieved, Davis 2012). Injured horses are often unwilling to cooperate reviewed, the patient details removed and collated in a making a thorough physical examination of an area that is randomised order by one of the authors (C.P.C.). Cases were already hard to assess even more difficult (Tremaine 2004; excluded from the study if the radiographic or CT Beard 2009; Beccati et al. 2011; Auer 2012) and hence examination did not include the area of the main fracture. diagnosis without further tests challenging. Diagnosis and The radiographic and CT examinations were evaluated by treatment planning is therefore typically based on diagnostic two of the authors (R.W. and F.V.). All radiographic images imaging findings (Tremaine 2004; Furst€ et al. 2010; Auer 2012). were evaluated first, followed by all CT images to assure that Radiographic examination is most often used as a first both modalities would not influence each other’s diagnosis. A

standardised evaluation form was used to describe the The CT studies all included a series in bone algorithm and different fractures: the visibility of an injury (Yes or No), soft in 14 cases an additional post-processing standard/soft-tissue tissue involvement (Yes or No), the location of the injury (the algorithm was available. In one case performed on a involved bones), the fracture type (single or multiple (based standing horse a motion artefact was present; the artefact on location); simple or comminuted; open or closed), the however did not obliterate the region of interest. number of fragments, the involvement of surrounding The radiographic and CT localisation and classification of anatomical structures and additional remarks (subjective the fractures is represented in Figure 1 and Table 1. In 3/18 assessment of the quality of the study as regard to the cases the evaluations of the radiographic examination fracture present). To be able to reach a consensus in concluded no injuries were visible, whereas the CT evaluation classification between the observers based on their reading of these cases showed: a depressed fracture in the temporal of the images, they were asked to describe the fractures and and parietal bone with multiple displaced fragments in a 2- the size, shape and displacement of the fragments. The month-old colt (Case 4), a comminuted fracture of the floor, observers had no knowledge of the horse’s identity, clinical septum and walls of the sphenopalatine sinuses in a 2-year- history, clinical presentation, surgical or pathologic findings old colt (Case 3) and an older fracture with periosteal and final diagnosis. reaction of the most apical part of the tooth alveolus of the The radiographic and CT evaluations of the observers fractured element 410 in a 6-year-old gelding (Case 12). were recorded and compared. In case of disagreement on In the remaining 15/18 cases a fracture was observed the classification of the fractures, the written descriptions radiographically, but the detection of soft tissue involvement were compared to reach a consensus on the correct (swelling and/or gas) on the radiographs was not detected in classification of the fractures, by one of the authors (C.P.C.). 3/15 cases (case 1, 2, 5; Fig 2). The location and extension of the fracture was Results underestimated in 7/15 cases where a fracture was detected radiographically. In one of these cases (Case 16) obvious Eighteen cases fulfilled the inclusion criteria for this study. fracture associated changes of the vertical ramus of the These included eight stallions, two colts, three geldings and mandible was present, but a non-displaced, simple, fracture five mares, with a median age of 6 years (range: 2 months– of the rostral body, which was not included in the 16 years). There were 11 Warmbloods, three Thoroughbreds, radiographic exam, was missed. In the other six cases (case two ponies, an Arabian and a French Trotter. 5, 6, 7, 8, 17, 18) the fracture extension was hidden due to The radiographic studies were acquired using computed superimpositions on the radiographs (Figs 3 and 4). In one radiography systems (Ghent University: Konica Minolta1; case (Case 8), the fracture extended further caudal to Rossdales: Agfa ADC NX2) and the number of radiographs per include the frontal bone, in addition to the involvement of case ranged from 1 to 8 views with a median of 5. The used the nasal and maxillary bone, which was identified radiographic protocols were at the discretion of the attending radiographically. In five cases (Case 5, 6, 7, 17, 18), fractures veterinarian of the case. All radiographs were used for this were located in the caudodorsal part of the skull involving study. From the standard projections (latero-lateral, ventro- the temporal bone (Case 5, 6, 7; Fig 3) or the condylar dorsal, leftventral-rightdorsal-oblique and rightventral-leftdorsal- process of the mandible (Case 17, 18; Fig 4). In addition to oblique), in seven cases all four projections, in six cases three underestimating the number of bones involved, the projections, in three cases two projections and in two cases involvement of the temporomandibular joint (TMJ) was not one projection, were available. In 15 cases additional detected on radiography in these cases. radiographs were included: in 12 cases these were additional standard projections and in eight cases additional intra-oral or the so-called skyline projections (without passing the midline, Rad 2; CT 2 Rad 0; CT 1 e.g. a rostral45°ventral30°lateral-caudodorsolateral-oblique Rad 4; CT 4 projection for the temporomandibular joint). The observers had no remarks on the quality of the radiographic study in 14 cases. In four cases additional ventrodorsal (two cases) or intra-oral (two cases) projections were suggested to complement the radiographic examination. 3 Two four-slice, helical CT scanners, a Lightspeed QX/I at Rad 2; CT 3 Ghent University and a Somatom Volume Zoom 44 at Rossdales, were used for this study. At Ghent University the horses were scanned under general anaesthesia and at Rossdales horses were scanned under standing sedation. The in-house protocols for equine head imaging were used (120 kV, 160 mAs, pitch 1, 1.25– 2.5 mm slices, 512 9 512 matrix, scan FOV between 192– 403 mm, bone and standard algorithm at Ghent University and 120 kV, 167–220 mAs, pitch 1, 2 mm slices, 512 9 512 Rad 4+1*; CT 5 Rad 1*; CT 0 matrix, scan FOV between 254–500 mm, bone and soft tissue algorithm at Rossdales). Rad 1; CT 1+2* Fourteen CT studies were performed as part of the clinical Fig 1: Location of the fractures as detected and diagnosed with work-up and four studies were performed with owner’s radiography and CT. *Fracture differently classified between consent after euthanasia. radiography and CT.

TABLE 1: Case details, radiographic (included standard projections + additional projections) and CT (included B: bone and S: standard algorithm) protocols, and radiographic and CT fracture evaluation of 18 skull fracture cases

Case, Gender, Modality/ Injury Soft tissue Single/ Open/ Age Protocol visible involvement Location Multiple Type Closed Fragments

1, stallion, 6 m Rad.4 + 3 Yes No 15, 16 Single Comm. Closed 0 CT B + S Yes Yes 15, 16 Single Comm. Closed 10+ 2, mare, 8 m Rad.3 + 1 Yes No 15, 16 Single Comm. Closed 4 CT B+S Yes Yes 15, 16 Single Comm. Open 6+ 3, stallion, 2 y Rad.3 + 1No/ / / / / / CT B + S Yes Yes 16 Single Comm. Open 3 4, stallion, 2 m Rad.3 No / / / / / / CT B + S Yes No 10, 11 Single Depress. Closed 4 5, stallion, 10 y Rad.2 + 3 Yes No 18 Single Simple Closed 2 CT B + S Yes Yes 10, 18 Multiple Comm. Closed 5+ 6, stallion, 2 m Rad.4 + 1 Yes Yes 4, 6 Single Comm. Open 3+ CT B Yes Yes 4, 6, 10 Multiple Comm. Open 10+ 7, stallion, 15 y Rad.3 Yes Yes 6 Single Comm. Closed 8+ CT B + S Yes Yes 4, 6, 10 Multiple Comm. Closed 10+ 8, stallion, 7 y Rad.4 + 1 Yes Yes 2, 3 Multiple Simple Closed 1 CT B + S Yes Yes 2, 3, 6 Multiple Comm. Open 10+ 9, gelding, 4 y Rad.1 Yes Yes 2 Multiple Simple Open 2+ CT B Yes Yes 2 Multiple Comm. Open 5 10, gelding, 14 y Rad.4 Yes Yes 3 Single Simple Open 0 CT B + S Yes Yes 3 Single Comm. Open 4 11, stallion, 6 y Rad.4 + 4 Yes Yes 1, 3 Multiple Comm. Closed 3 CT B + S Yes Yes 1, 3 Multiple Comm. Open 3 12, gelding, 6 y Rad.2 + 5No/ / / / / / CT B Yes No 20 Single Simple* Closed 3 13, mare, 7 y Rad.4 + 1 Yes Yes 20 Single Simple* Closed 0 CT B + S Yes Yes 20 Single Simple* Closed 1 14, stallion, 1 y Rad.3 + 1 Yes Yes 20 Multiple Comm. Open 4 CT B + S Yes Yes 20 Multiple Comm. Open 10+ 15, mare, 16 y Rad.2 + 2 Yes Yes 20 Single Simple* Open 1 CT B + S Yes Yes 20 Single Simple* Open 2 16, mare 6 m Rad.4 + 2 Yes Yes 19 Single Comm. Open 6+ CT B Yes Yes 19, 20 Multiple Comm. Open 10+ 17, stallion, 5 y Rad.3 + 2 Yes Yes 20 Multiple Simple Open 2 CT B + S Yes Yes 18, 19, 20 Multiple Comm. Open 10+ 18, mare, 16 y Rad.3 + 6 Yes Yes 19, 20 Multiple Comm. Open 6 CT B + S Yes Yes 18, 19, 20 Multiple Comm. Closed 10+

Legend for the localisation of the fractures: 1 = Incisive bone; 2 = Nasal bone; 3 = Maxilla; 4 = Zygomatic bone; 5 = Lacrimal bone; 6 = Frontal bone; 7 = Palatine bone; 8 = Vomer; 9 = Presphenoid bone; 10 = Temporal bone; 11 = Parietal bone; 12 = Interparietal bone; 13 = Occipital bone (squamous part); 14 = Occipital bone (lateral part); 15 = Occipital bone (basilar part); 16 = Sphenoid bone; 17 = Coronoid process; 18 = Condylar process; 19 = Ramus mandibula; 20 = Body mandibula; 21 = Hyoid apparatus.

In 4/10 cases (Case 5, 6, 7, 16) diagnosed with multiple Discussion fractures on CT the observers diagnosed only a single fracture ﬁ with radiography. In the cases where no fractures were identi ed In 5/13 cases (Case 5, 8, 9, 10, 17) diagnosed with a radiographically, the fractures were subtle and located in comminuted fracture on CT the observers diagnosed a anatomical complex areas. Interestingly although reviewers simple fracture with radiography. were aware of the inclusion criteria, some fractures remained In 3/15 cases (Case 2, 8, 11) a closed fracture was unnoticed. As previously described for distal limb fractures, diagnosed radiographically, which was revealed to be open the combination of lesion severity and the degree of on CT examination. In 1/15 cases (Case 18) the fracture was superimposition can cause fractures to go unnoticed (Crijns diagnosed open with radiography and closed with CT. et al. 2014). However, subtle, previously unnoticed lesions on In 14/15 cases the number of fragments was underestimated radiography can retrospectively be suspected if their with radiography. Only in one case (Case 11) involving only presence has been demonstrated using CT (Crijns et al. 2010, large fragments observers were able to determine a similar 2014). Moreover, the general limiting principles of number of fragments on both radiographic and CT images. radiography need to be considered. Firstly, the x-ray beam Involvement of additional structures (such as the should be parallel to a fracture line and, secondly, infraorbital canal, foramina, temporomandibular joint, tooth, summation and superimposition should not interfere with the eye, airway, nasolacrimal duct) was only suspected on interpretation of the radiographs (Chacon et al. 2003; Bar-Am radiography based on the localisation of the lesion, but were et al. 2008; Butler et al. 2008b). An additional limitation only deﬁnitively diagnosed by CT. related to equine patients, is the inability to record the entire

a) b)

c) d)

Fig 2: Case 2, laterolateral (a, rostral is to the left) and ventrodorsal (b, rostral is to the top and right is to the left) radiographic projections of the cranium and transverse (c and d, right is to the left) computed tomographic images. On the radiographic images, (a) only a small step just caudal to the spheno-occipital suture line between the basisphenoid and basioccipital bones is detected (a: arrow) and a curved radiolucent line runs in a longitudinally through the basisphenoid and basioccipital bones (b: arrows). On the CT images, at the level of the TMJ (c) a heavily comminuted fracture of the basisphenoid bone (arrowheads) is detected and just cranial to the inner ears (d) only a single fracture line is detected in the basioccipital bone (arrowhead). Note the gas opacities inside the cranium not detected on the radiographs (c and d: arrows). skull on a single image as in small animals (Bar-Am et al. fractures in this region compared to radiography is in line 2008). Malocclusion of the teeth or misalignment of the bone with previous published case reports and smaller case are likely consequences of trauma/fracture/luxation and series (Gardelle et al. 1999; Lischer et al. 2005; Beccati et al. most easily seen single images of the entire skull. 2011). The main limitation of radiography in these In the case of the 2-month-old foal with a single, complex anatomical regions is a broad variety of depressed, comminuted, temporal and parietal bone opacities, contrary to lesions involving the paranasal sinuses fracture, considering the foal’s age and in the absence of (O’Leary and Dixon 2011) or the mandible (Huggons et al. visible displacement of the fragments on radiography, this 2011). fracture line was misinterpreted as an open fontanel. The Involvement of the TMJ was underestimated normal radiographic appearance of the fontanels has not radiographically, as fractures were located in 80% of the been described in horses, and only limited information is cases in the axial portion of the joint. Only in one case (Case available on fusion and obliteration times (Butler et al. 2008a). 5) was the complete width of the TMJ involved in the lesion. Further studies describing these normal open fontanels would Although specific projections of the TMJ were included for this be interesting and useful in such cases. case, the radiographic study underestimated this lesion. As In the remaining cases fractures were diagnosed with trauma is one of the reasons for the development of TMJ both modalities. The ability of CT to more accurately disease, an initial correct diagnosis of the involvement of the diagnose the location and extent of fractures compared to TMJ is therefore of prognostic importance to avoid long-term radiographs was seen in 40% of the cases. In 44% of the sequelae (Weller et al. 2002; Chacon et al. 2003; Sanders cases multiple fractures on CT were diagnosed as single et al. 2014). fractures radiographically. In most of these cases the In line with these results, the number of fragments was fractures were located in the caudodorsal part of the skull, underestimated on radiography in all but one case. including the complex regions of the TMJ, the orbita and Fragments were missed with radiography in cases classified as the skull base. The ability of CT to diagnose more extensive simple but also when classified as comminuted. Reviewing

a) b)

c) d)

e) f)

Fig 3: Case 7, laterolateral (a, rostral is to the left) and rightventral-leftdorsal-oblique (b, rostral is to the left) radiographic projections of the nasofrontal region, and transverse (c, d, e and f, right is to the left) CT images. On the laterolateral projection (a) no evidence of a bony injury is detected, on the rightventral-leftdorsal oblique projection (b) only two thin radiolucent lines (arrows) are superimposed over the region of the right orbita. The transverse CT images at the level and just caudal to the orbita, showing multiple and several displaced fracture lines surrounding the right orbita (c, d, and e: arrows), and a singular fracture line in the frontal bone (e: arrowheads). On the transverse CT image at the level of the temporomandibular joints, the temporomandibular joint is involved in the fracture, as multiple fracture lines are present in the temporal bone (f: arrow). specific fragments, two factors led to diagnostic differences degree of comminution, and the involvement of additional between radiography and CT in detecting fragments. Firstly, structures in a fracture (Beard 2009; Auer 2012). some fragments (small and large) were not recognised on Contrary to human medicine where CT suites are widely radiography (Case 5, 6, 8, 16, 17, 18), and secondly, in the accessible and CT examinations are more routinely used in absence of displacement, several smaller fragments cases of suspected head trauma (Schuknecht and Graetz identified on CT could appear as one larger fragment on 2005), the availability and the use of CT in equine medicine radiography (Case 2, 9, 14). are limited. A shortcoming of this study is the inclusion of only a Although the final outcome of the individual cases was sub selection of cases diagnosed with a skull fracture. Only not included in this study, the decision to follow either a cases that underwent both a radiographic and a CT conservative or a surgical treatment, and the estimation of examination met the inclusion criteria of the study. This the prognosis are mainly influenced by the interpretation and inadvertently led to an inclusion bias of cases in which perception of a fracture (Schaaf et al. 2008; Beard 2009; radiographic findings were insufficient in explaining the clinical Auer 2012). Regarding the surgical guidelines for skull signs. In the absence of a reliable gold standard in all cases, fractures described in several publications (Tremaine 2004; sensitivity and specificity of the modalities were not calculated. Beard 2009; Furst€ et al. 2010; Auer 2012), preoperative The heterogeneity of the radiographic examinations can considerations vary depending on localisation, configuration, also be considered a shortcoming of this retrospective

a) b)

c) d)

e) f)

Fig 4: Case 18, rightventral-leftdorsal-oblique radiographic projections (rostral is to the left) of the rostral part of the skull (a) and left mandibular ramus (b), and transverse (c, d and e, right is to the left) and parasagittal (f, rostral is to the left) CT images. On the radiographic images, several sharp delineated fracture lines are present in the left body of the mandible (a: arrows) and one sharp delineated fracture line is detected in the vertical ramus of the left mandible running in a ventrodorsal direction (b: arrow). On the CT images, several sharp delineated fracture lines are present in both the left and right mandibular body in the caudal part of the mandibular symphysis (c: arrows). In the region of the TMJ an area of comminution is present in the left coronoid process just ventral to the level of the TMJ (d: circle), a separated fragment is present at the axial portion of the left condylar process (e: circle). In (f) at the level of the left TMJ, a sharp delineated thin fracture line is running in a dorsoventral direction in the left mandibular ramus (arrows) and a wider, more irregular fracture line (circle) surrounded by two sharp delineated thin fracture lines (arrowheads) is running in a rostrocaudal direction.

study. However, standardising the radiographic examination tomography in dogs and cats with maxillofacial trauma. Vet. Surg. is considered to lower the ability to visualise specific 37, 294-299. structures (Bar-Am et al. 2008). Variation of the fracture Beard, W. (2009) Fracture repair techniques for the equine mandible types and specific (e.g. unilateral) lesion presentation can and maxilla. Equine Vet. Educ. 21, 352-357. therefore justify the lack of standardisation in the Beccati, F., Angeli, G., Secco, I., Contini, A., Gialletti, R. and Pepe, M. radiographic protocol in this study. Furthermore, performing (2011) Comminuted basilar skull fracture in a colt: Use of computed tomography to aid the diagnosis. Equine Vet. Educ. 23, the radiographic examinations under clinical conditions on 327-332. standing horses limits the ability of producing additional Butler, J.A., Colles, C.M., Dyson, S.J., Kold, S. and Poulos, P. (2008a) projections due to the uncooperative nature or discomfort Chapter 9 the head. In: Clinical Radiology of the Horse, Eds: J.A. of the patients. Reviewing the CT examinations for which Butler, C.M. Colles, S.J. Dyson, S. Kold and P. Poulos, Wiley- additional intra-oral radiographic projections were Blackwell, Oxford. pp 413-449. suggested (14 and 17), revealed that both cases involved Butler, J.A., Colles, C.M., Dyson, S., Kold, S. and Poulos, P. (2008b) bilateral multiple comminuted (one severely displaced) Chapter 1 General principles. In: Clinical Radiology of the Horse, fractures of the mandibular body. In one of these cases an 3rd edn., Eds: J.A. Butler, C.M. Colles, S. Dyson, S. Kold and P. Poulos, Wiley-Blackwell, Oxford. pp 1-36. intra-oral projection, of the most rostral part of the Caldwell, F.J. and Davis, H.A. (2012) Surgical reconstruction of a mandible, was included in the radiographic study. Although severely comminuted mandibular fracture in a horse. Equine Vet. an intra-oral projection would diminish the superimposition Educ. 24, 217-221. of the maxilla over the fractured mandible, patients Chacon, G.E., Dawson, K.H., Myall, R.W. and Beirne, O.R. (2003) A discomfort most likely prevented these projections to be comparative study of 2 imaging techniques for the diagnosis of taken of more caudal structures. Moreover, taking intra-oral condylar fractures in children. J. Oral Maxillofac. Surg. 61, 668-672. projections in the presence of an unstable, (partial) Creasman, C.N., Markowitz, B.L., Kawamoto, H.K., Cohen, S., displaced fracture could be contraindicated. Kioumehr, F., Hanafee, W.N. and Shaw, W.W. (1992) Computed- In conclusion, CT gives more information regarding tomography versus standard radiography in the assessment of fractures of the mandible. Ann. Plast. Surg. 29, 109-113. fracture configuration, structures involved and severity when compared with radiography. Therefore, CT should be the Crijns, C.P., Gielen, I.M.V.L., van Bree, H.J.J. and Bergman, E.H.J. (2010) The use of CT and CT arthrography in diagnosing equine stifle modality of choice for surgical planning and prognosis. injury in a Rheinlander gelding. Equine Vet. J. 42, 367-371. Crijns, C.P., Martens, A., Bergman, H.J., van der Veen, H., Duchateau, Authors’ declaration of interests L., van Bree, H.J.J. and GIelen, I.M.V.L. (2014) Intra-modality and inter-modality agreement in radiography and computed No conflicts of interest have been declared. tomography of equine distal limb fractures. Equine Vet. J. 46, 92- 96. Furst,€ A., Jackson, M., Kummerle, J., Bettschart-Wolfensberger, R. and Ethical animal research Kummer, M. (2010) Summary of current therapeutic measurements in head fractures of horses. Pferdeheilkunde 26, 503-514. Retrospective study of case records. Gardelle, O., Feige, K., Geissbuhler, U., Geyer, H., Schmucker, N., Sydler, T. and Kaser-Hotz, B. (1999) The use of computed Source of funding tomography in two equine patients with basilar skull fractures. Schweiz. Arch. Tierheilkd. 141, 267-272. None. Henninger, R.W., Beard, W.L., Schneider, R.K., Bramlage, L.R. and Burkhardt, H.A. (1999) Fractures of the rostral portion of the mandible and maxilla in horses: 89 cases (1979-1997). J. Am. Vet. Authorship Med. Assoc. 214, 1648-1652. C. P. Crijns contributed to study design, study execution, data Huggons, N.A., Bell, R.J.W. and Puchalski, S.M. (2011) Radiography and computed tomography in the diagnosis of nonneoplastic equine analysis and interpretation, and preparation of the mandibular disease. Vet. Radiol. Ultrasound. 52, 53-60. manuscript. R. Weller contributed to study design, study Lischer, C.J., Walliser, U., Witzmann, P., Eser, M.W. and Ohlerth, S. execution and data analysis and interpretation. L. Vlaminck, (2005) Fracture of the paracondylar process in four horses: S. Schauvliege, S. Powell, H. van Bree and I. Gielen Advantages of CT imaging. Equine Vet. J. 37, 483-487. contributed to study design. F. Verschooten contributed to Marinaro, J., Crandall, C.S. and Doezema, D. (2007) Computed study execution and data analysis and interpretation. All tomography of the head as a screening examination for facial authors gave their final approval of the manuscript. fractures. Am. J. Emerg. Med. 25, 616-619. O’Leary, J.M. and Dixon, P.M. (2011) A review of equine paranasal sinusitis. Aetiopathogenesis, clinical signs and ancillary diagnostic Manufacturers’ addresses techniques. Equine Vet. Educ. 23, 148-159. 1Konica Minolta, Zaventem, Belgium. Ramirez, O., Jorgensen, J.S. and Thrall, D.E. (1998) Imaging basilar skull 2AGFA Gevaerts Ltd., Mortsel, Belgium. fractures in the horse: A review. Vet. Radiol. Ultrasound. 39, 391- 3Lightspeed QX/I, GE Medical Systems, Milwaukee, Wisconsin, USA. 395. 4 Siemens Somatom Volume Zoom 4, Camberley, Surrey, UK. Sanders, R.E., Schumacher, J., Brama, P.A.J., Zarelli, M. and Kearney, C.M. (2014) Mandibular condylectomy in a standing horse for treatment for osteoarthritis of the temporomandibular joint. Equine References Vet. Educ. 26, 624-628. Auer, J.A. (2012) Craniomaxillofacial Disorders. In: Equine Surgery,Eds.: dos Santos, D.T., Silva, A.P.A.C., Vannier, M.W. and Cavalcanti, M.G.P. Auer J.A., and Stick J.A., Elsevier Saunders, St. Louis, Missouri. p 1531. (2004) Validity of multislice computerized tomography for diagnosis of maxillofacial fractures using an independent workstation. Oral Bar-Am, Y., Pollard, R.E., Kass, P.H. and Verstraete, F.J.M. (2008) The Surg. Oral Med. Oral Pathol. 98, 715-720. diagnostic yield of conventional radiographs and computed

Schaaf, K.L., Kannegieter, N.J. and Lovell, D.K. (2008) Management of Weller, R., Maierl, J., Bowen, I.M., May, S.A. and Liebich, H.G. (2002) equine skull fractures using ﬁxation with polydioxanone sutures. The arthroscopic approach and intra-articular anatomy of the Aust. Vet. J. 86, 481-485. equine temporomandibular joint. Equine Vet. J. 34, 421-424. Schuknecht, B. and Graetz, K. (2005) Radiologic assessment of maxillofacial, Wollanke, B., Gerhards, H. and Cronau, M. (2006) Diagnosis and mandibular, and skull base trauma. Eur. Radiol. 15, 560-568. therapy of periorbital diseases in horses: Indication for computed tomography (CT) or magnetic resonance tomography (MRT). Tremaine, H. (2004) Management of skull fractures in the horse. In Pract. 26, 214-222. Pferdeheilkunde 22, 431-438.

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The app will be regularly updated with new content and Brannick, E.M., DeWilde, C.A., Frey, E., Gluckman, T.L., Keen, J.L., initiatives that will be highlighted on its social media feeds. Larsen, M.R., Mont, S.L., Rosenbaum, M.D., Stafford, J.R. and Helke, K.L. (2015) Taking stock and making strides toward wellness in the Vets in Mind app is available via the Apple and Android veterinary workplace. J. Am. Vet. Med. Assoc. 247, 739-742. App stores and the Consortium can be also be reached by ﬁ ’ Diener, E.D., Emmons, R.A., Larsen, R.J. and Grif n, S. (1985) The email to [email protected] or via the VetsInMind s Satisfaction with life scale. J. Pers. Assess. 49, 71-76. Instagram, Twitter and Facebook accounts. Stoewen, D.L. (2015) Suicide in veterinary medicine: let's talk about it. † N. ENDENBURG* and M. JOHNSTON Can. Vet. J. 56, 89-92. *Division Human-Animal Relations, Department of Thomas, L.R., Ripp, J.A. and West, C.P. (2018) Charter on physician Animals in Science and Society, Faculty of Veterinary well-being. JAMA 319, 1541-1542. Medicine, Utrecht University, Utrecht, The Netherlands; Van Houtert, E.A., Endenburg, N., Wijnker, J.J., Rodenburg, B. and † Vermetten, E. (2018) The study of service dogs for veterans with and Vetstream Ltd, Bartlow, Cambridge, UK post-traumatic stress disorder: a scoping literature review. Eur. J. Psychotraumatol. 9, Suppl. 3, 1503523.

References Bartram, D.J. and Baldwin, D.S. (2008) Veterinary surgeons and suicide: inﬂuences, opportunities and research directions. Vet. Rec. 16, 36.

Original Article Behavioural assessment of pain in 66 horses, with and without a bit W. R. Cook†* and M. Kibler‡ †Department of Clinical Sciences, Cummings School of Veterinary Medicine, Tufts University, North Grafton, Massachusetts; and ‡Department of Mathematics and Computer Science, Washington College, Chestertown, Maryland, USA *Corresponding author email: [email protected] Present address: W. R. Cook, Cummings School of Veterinary Medicine Clinical Sciences, Chestertown, Maryland, USA

Keywords: horse; bit; pain; pain-related behaviour; proprioception; stereotypic behaviour; welfare; poor performance

Summary subjected to scrutiny until quite recently (Cook 1999). In a Horses can be ridden with or without a bit. Comparing the review of equine pain assessment, the absence of data on behaviour of the same horse in different modes constituted a ‘abnormal bit behaviour’ [sic] was noted by Ashley et al. ‘natural experiment’. Sixty-nine behaviours in 66 bitted horses (2005). Since then, three studies have compared ridden horse were identified as induced by bit-related pain and behaviour, with and without a bit. First, two unschooled 2- recognised as forms of stereotypic behaviour. A prototype year-old horses in a 10-day period of foundational training questionnaire for the ridden horse was based on 6 years of performed “at least as well, if not better” without bits as two feedback from riders who had switched from a bitted to a matched horses in snaffle bridles (Quick and Warren-Smith bit-free bridle. From a template of 69 behavioural signs of 2009). Second, four mature horses, in their maiden bit-free pain derived from answers to the questionnaire, the number test, exhibited statistically improved ridden behaviour (Cook of pain signals shown by each horse, first when bitted and and Mills 2009). In two concurrent four-minute tests, first bitted then bit-free, was counted and compared. After mostly then bit-free, riders’ scores increased from a mean of 37 multiple years of bit usage, the time horses had been bit- (‘fairly bad’)to64(‘satisfactory’). Finally, a study of 16 free ranged from 1 to 1095 days (median 35). The number of therapeutic riding horses showed significantly more negative pain signals exhibited by each horse when bitted ranged behaviours when bitted and positive behaviours when bit- from 5 to 51 (median 23); when bit-free from 0 to 16 (median free (Carey et al. 2016). 2). The number of pain signals for the total population when Pain studies in animals have not generally included bitted was 1575 and bit-free 208; an 87% reduction. removal of the pain’s source. The arrow of direction in Percentage reduction of each of 69 pain signals when bit- assessing most management interventions (e.g. castration) is free, ranged from 43 to 100 (median 87). The term ‘bit from painless to painful. In the current study, the direction lameness’ was proposed to describe a syndrome of was reversed. Bit usage is an elective and almost daily lameness caused by the bit. Bit pain had a negative effect intervention during many horses’ working lives. Assessment of on proprioception, i.e. balance, posture, coordination and its effect on welfare is overdue. movement. Only one horse showed no reduction in pain As bits have been standard equipment for millennia, they signals when bit-free. The welfare of 65 of 66 horses was are widely assumed to be indispensable and ethically enhanced by removing the bit; reducing negative emotions justified. This being so, an opinion by welfare researchers is (pain) and increasing the potential to experience positive cited ... “Most horses exhibit clear behavioural evidence of emotions (pleasure). Grading welfare on the Five Domains aversion to a bit in their mouths, varying from the bit being a Model, it was judged that – when bitted – the population mild irritant to very painful” (Mellor and Beausoleil 2017). The exhibited ‘marked to severe welfare compromise and no same authors observe that evidence of aversion is available enhancement’ and – when bit-free – ‘low welfare compromise to all who seek by comparing the open mouth, head tossing and mid-level enhancement.’ The bit-free data were and restricted jaw angle of many bitted horses – clearly consistent with the ‘one-welfare’ criteria of minimising risk and apparent on YouTube videos – with the absence of these preventing avoidable suffering. behaviours in videos of wild horses and of domestic horses when ridden bit-free or bridleless. The need for a list of ridden Introduction horse behaviours to be developed was noted by Hall et al. (2013). Pain in animals is defined as an aversive sensation caused by The study objective was to start answering six questions: actual or threatened tissue damage; a negative mental • What behaviours are caused by the bit? state. Pleasure is defined as fulfilment of a biological drive for • How prevalent are they? comfort and safety; a positive mental state. Current animal • How many bit-induced behaviours might one horse welfare thinking (Mellor 2015a) refers to ‘pleasure’ as a exhibit? ‘positive affective experience’ (Table 1). The term ‘affect’ • Are they reversible when the bit is removed? describes emotion (feeling), either positive or negative. It • Is a horse’s welfare improved by removal of the bit? encompasses ‘motivation’; an animal’s urge to move • Can a horse be controlled without a bit? towards or away from a stimulus, i.e. stereotaxis. Used since the Bronze Age, metal bits have been The null hypothesis was that removal of the bit would accepted as part of the furniture of horsemanship and not cause no behavioural change.

© 2018 The Authors Equine Veterinary Education published by John Wiley & Sons Ltd on behalf of EVJ Ltd This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. 552 EQUINE VETERINARY EDUCATION / AE / OCTOBER 2019

TABLE 1: Prevalence of 69 pain indices in 66 horses, when bitted and bit-free. The mean reduction when bit-free was 85% (range 43– 100) with a median of 87%. Many of the bit-induced pain indices jeopardised the safety of both horse and rider

Number of number of Inferred likelihood of horse having POSITIVE AFFECTIVE Order horses horses Reduction EXPERIENCES e.g., pleasures of safety, conﬁdence, comfort, when affected affected when compliance, enthusiasm, motivation following removal of bitted PAIN INDICES BITTED BIT-FREE bit-free (%) the bit and cessation or easement of pain

1 Hates the bit 53 0 100 The relief, pleasure and comfort of being without pain 2 FRIGHT: 46 4 87 One of the five major categories of fear (the five ‘F’s), replaced by calmness, ease and comfort 3 Stiff-necked 45 7 84 Freedom of the head: Ability to balance; smoothness and fluidity in the ‘way of going’ 4 Lack of control 43 6 86 Horse/rider high accident hazard replaced by willing cooperation, harmony and partnership 5= Resents bridling 41 3 93 Drops head eagerly into bridle; exhibits enthusiasm for work 5= Above the bit 41 3 93 Able to select the physiologically most comfortable (optimally balanced) head position 6 Muzzle rubbing 40 9 77 Relief from the persistent irritation and distraction of facial neuralgia 7= Head shaking 37 8 78 As above for ‘muzzle rubbing’ - the relief from nerve ache 7= Unfocused 37 1 97 Focused; not distracted; ‘listens’ to and complies with rider’s signals 8 FLIGHT 35 1 97 Contentment; energy conservation; no propensity to bolt, rush or run away 9= FIGHT 34 2 94 Calm, quiet, cooperative and willingly offers compliance 9= Pig-rooting 34 2 94 See ‘fight’ above: Does not grab the bit and snatch reins from rider’s hands 10 Difficult to steer 33 8 76 Ability to balance; steers straight and turns comfortably (also see ‘lack of control’ above) 11= Stiff or choppy stride 32 2 94 Enjoys the natural rhythm of motion (also see ‘stiff-necked’ above) 11= Reluctant to rein-back 32 10 69 Return of normal agility; one of many signs of reduced ‘bit lameness’ 12 Tail swishing 31 1 97 Removal of discomfort; tail movement in synchrony with spinal movement 13= Hair-trigger response 29 0 100 Calm and confident as opposed to ‘highly strung,’ anxious to bit and apprehensive 13= Sneezing & snorting 29 13 55 Restoration of normal breathing pattern; reduction of nasal irritation (facial neuralgia) 14 Yawning 28 4 86 Absence of yawning suggestive of reduced need to ease/interrupt pain signals (see facial neuralgia above) 15 Slow learner 27 1 96 Return of ability to learn - a vital survival strategy (see unfocussed above) 15 Uncooperative 27 3 89 See ‘fight’ above 15 Heavy on the forehand 27 6 78 Unhampered ability to balance, return of normal agility, elimination of stress and pain 16 Fails to stand still 26 0 100 Return of species specific default behaviour of calmness and contentedness 17 Pulling on bit 26 0 100 No need to defend itself from the bit and become unbalanced in the process 18= Grazing on the fly 25 11 56 Less need to ‘interrupt’ pain signals (see ‘yawning’ above) at exercise 18= Inverted frame 25 5 80 No pain - no high head carriage - return of ability to balance 19= Dislikes wind/rain/sunlight 24 10 58 Relief from trigeminal hypersensitivity 19= Tilts head at exercise 24 5 79 Proper balance with no need to try and avoid bit pain 19= Fails to maintain 24 4 83 Engaged, lively, energised, exhibits vitality of fitness trot or canter 20= Difficult to mount 23 3 87 Reduced anxiety and apprehension 20= Grabs the bit 23 0 100 No need for defensive behaviour at exercise 20= Lacks courage 23 5 78 Confident, engaged and curious about its environment 21= Napping 22 4 82 Reduction of fear; reduced pain increases comfort (see ‘Freeze’) 21= Stumbling 22 7 68 Reduction of ‘bit lameness’ with unfettered proprioception enabling a horse to keep itself upright and safe 22= FREEZE 21 4 81 Keen to explore. Relief from the ‘frozen’ state of a prey animal when attacked by a predator 22= Resents unbridling 21 1 95 Optimism rather than pessimism (see ‘hates the bit’ above)

TABLE 1: Continued

22= Behind the bit 21 1 95 Adopts head position based on proprioceptive signals (see ‘above the bit’) 22= Head shyness 21 12 43 Abatement of trigeminal hypersensitivity, hyperalgesia or neuralgia 22= Salivates excessively 21 2 90 A relatively dry mouth betokens contentedness at exercise 23= Bucking or bounding 20 3 85 Less pain, more comfort 23= Lazy or dull 20 4 80 Engaged aliveness 23= Heads for the stable 20 6 70 Relishes exercise, fulﬁls biological drive and need for movement 23= Jigging 20 1 95 Walks quietly and contentedly 24= Unfriendly in stable 18 2 89 Return of normal (social) behaviour 24= Anxious eye 18 2 89 ‘Soft’ (rounded) eye - an indicator of comfort 25= Ear pinning at exercise 17 4 76 Non-aggression equates with the default social behaviour of the species 25= Open mouth (gaping) 17 2 88 Closed mouth and sealed lips; oral vacuum restored; default condition for unobstructed airway at exercise 25= Lolling tongue 17 0 100 Another return to physiological and behavioural norm 25= Reluctant to change lead 17 5 71 Return of normal agility with correction of ‘bit lameness’ 26 Bites at tack or 16 0 100 Reduced facial neuralgia enables disposition to move beyond other horses neutral to a more positive emotional state 27 Scuffs hind hooves 15 7 53 Soundness of limb returns with correction of ‘bit lameness’ 28 Backing-up 14 1 93 See ‘fails to stand still’ 29 Multiple wrinkles 13 2 85 Relaxation of tension with elimination of pain around muzzle 30 Crossing the jaw 13 1 92 As above - return to ‘normal’ behaviour when on the move 31= Evades capture 12 2 83 Accepts rider as a member of its ‘herd’ or ‘band’ in paddock 31= Sweats excessively 12 1 92 No stress, less sweat 31= Over bends 12 0 100 Proprioceptively and physiologically comfortable head position 31= Tongue over bit 12 0 100 No need for defensive behaviour following removal of the bit, unobstructed breathing 31= Interfering 12 4 67 Another aspect of ‘bit lameness’ corrected 32 Rears 11 2 82 Reductionof bit-escape behaviour 33= Runs wild on bitted lunge 10 1 90 More comfortable 33= Lower lip slapping 10 3 70 More comfortable 33= Incoordination. 10 1 90 Unhampered proprioception corrects ‘bit lameness’ 34= Eyes water 9 2 78 Reduction of corneal pain (facial neuralgia) 34= Exercise triggers cough 9 2 78 Reduction of pharyngeal angina (trigeminal neuralgia) and/or inﬂammatory airway disease 34= Back problems 9 2 78 Relief of ‘bit-lameness’ 35 Retracts tongue 7 0 100 Return of default tongue position at exercise, oral vacuum, behind bit soft palate stability, unobstructed airway 36 Drops food 6 0 100 Elimination of ‘sore mouth’ (mandibular gingivitis) 37 Reluctant to drink 4 0 100 Ability to create an oral vacuum and relief of ‘sore mouth’ during ‘endurance’ test prevents dehydration

Upper case letters mark the five major categories of fear-induced behaviour (the five ‘F’s) in the questionnaire; i.e. fright, flight, fight, freeze and facial (trigeminal) neuralgia. Pain indices specific to the bit are shaded grey.

Method questions were posed using vernacular terms (Wemelsfelder et al. 2001). At the end of an 8-page manual for a bit-free Study design bridle, riders were informed that a questionnaire was Owner/rider assessment of horse behaviour, with and without a available for documenting behavioural changes. The bit; a longitudinal, retrospective, questionnaire-based study. The questionnaire was mailed on request or, more commonly, number of behavioural signs of pain in each of 66 horses when downloaded online. The 6-page questionnaire comprised bitted was compared with the number of signs when bit-free. signalment; 106 ‘yes/no’ questions about horse behaviour and signs of disease; and 10 questions describing a rider’s Questionnaire feelings about riding. It was completed twice; once when The questionnaire (Supplementary Item 1) was based on bitted and again when bit-free. From the answers, the 6 years’ feedback from 605 riders who had switched from a change in prevalence of 69 behaviours, occurring in not less bitted to a bit-free bridle (Cook 2003). As recommended, than 4 of 66 horses when bitted, was assessed (Table 1).

Population selection • The welfare grade for the population when bitted was Owner/riders volunteered their participation in the study. judged to be D/0 (marked to severe compromise and no Each horse served as its own control, inasmuch as its enhancement) and, when bit-free B/++ (low compromise behaviour was compared before and after removing the bit. and mid-level enhancement). Between 2002 and 2016, 96 questionnaires were received. • None of the riders experienced loss of control when bit- Sixty-six were completed correctly; a ‘usable’ rate of 69%. The free, quite the opposite. In only one horse was control inclusion criterion was that for each of the 69 behaviours unchanged. selected for analysis, a yes/no answer must have been entered for both bitted and bit-free periods. The null hypothesis was refuted: 65 out of 66 horses showed a change in behaviour following removal of the bit. Statistical analysis A matched pairs t-test was used to determine if there was Discussion change in the number of pain signals (pain indices) when bit- free. An alpha level of 0.05 was set for significance. The data support previous observations based on anecdotal evidence (Cook 2003). Welfare assessment Horses exhibit stereotaxis; a word derived from the Greek A numerical grading of behaviour was eschewed in favour of stereo, ‘hard, solid’. This fundamental property of (even) the Five Domains Model (Mellor and Beausoleil 2015; Mellor primitive life forms, also known as thigmotaxis, is defined as 2017). Welfare compromise was graded on a five-tier scale ‘the positive (or negative) response of a freely moving from A (no compromise) to E (very severe compromise). organism to cling to (or avoid) a solid object’. Indisputably, a Welfare enhancement was graded on a four-tier scale from bit is a ‘solid’ object. A horse is innately programmed to (try zero (no enhancement) to +++ (high-level enhancement). and) move away from (evade) the bit, i.e. to display negative stereotaxis. A definition for thigmotaxis (Greek: thigmo,’touch’) emphasises the point – “the motion or Results orientation of an organism in response to a touch stimulus”. The age of the population ranged from 3 to 24 years, with a When the touch is painful, stereotaxic stimuli are stronger. It mean of 10 years and a median of 8 (Table 2). Including half- follows that the equitation mantra requiring a horse to ‘ ’ breds, the breeds comprised Thoroughbreds (n = 21), accept the bit is misconceived. Expecting a horse to Arabians (n = 11), Warmbloods (n = 7), Tennessee Walking accept an oral foreign body is a biologically unrealistic Horses (n = 5), Appaloosas (n = 4), Clydesdales (n = 3) and expectation. fi others (n = 15). Gender distribution was male (n = 40; 39 Mason (2006) proposed a de nition of stereotypical ‘ geldings and one stallion) and female (n = 25). Categories by behaviour based on three causal mechanisms, i.e. repetitive predominant use were dressage (n = 22), pleasure (n = 21), behaviours induced by frustration, repeated attempts to ’ trail (n = 13), eventing (n = 5) and jumping (n = 5). All owners cope and/or CNS dysfunction . The reversibility of 69 ‘ rode ‘English’ style. Twenty-eight horses had been bitted for behaviours in 65 of the bitted horses indicates that CNS ’ ‘ ’ five or more years. The time a horse had been bit-free before dysfunction was not their cause but frustration and ‘ ’ the second assessment ranged from 1 to 1095 days (median attempts to cope are mechanisms consistent with the data. ’ 35; mean 108). Questionnaires were returned from North In Mason s words again, stereotypical behaviours are ‘ America (n = 46), UK (n = 14), Australasia (n = 3), Austria generally responses of normal animals to abnormal ’ ‘ fi (n = 1), France (n = 1) and Holland (n = 1). environments . In captive animals, they stem from ade cit in fi Bits used were snaffles, Pelhams and double bridles. The housing or husbandry, where a de cit means something that bit-free bridle used throughout was a crossunder (Dr.Cookâ)1 the animal would change if it could (e.g. a motivational fi fi Results are displayed in Tables 1–3 and Figure 1. Answers de cit linked with frustration; a health de cit linked with fi ’ to the six questions are summarised as follows: nausea or pain; or a safety de cit causing fear) . Observational evidence constitutes the foundation for • All 69 behaviours were caused by the bit, as judged by animal welfare assessment and this evidence – carefully their significant reduction in prevalence when the bit was observed – is objective, not subjective. “Contemporary removed. Excessive salivation was the only behaviour not animal welfare science understanding” accepts the need to caused solely by bit-induced pain, being also a reflex “focus on subjective experiences, known as affects, which response to an oral foreign body. collectively contribute to an animal’s overall welfare status” • Bit-induced behaviours, as a group, were highly prevalent. The (Mellor 2017). Inferences based on such observational total number of pain signals for the population when bitted evidence derive credibility from the underlying affective was 1575 and, when bit-free, 208; an 87% reduction. From 66 neuroscience in a process that “involves cautiously exercising horses, the number of horses exhibiting each behaviour scientifically informed best judgement” (Mellor and Beausoleil ranged from 53 (80% of the population) to 4 (6%) (Table 1). 2017). Thus, it is asserted that improvements in behaviour • The median number of behaviours per horse when bitted following removal of the bit enable inferences to be made was 23 (range 5–51); when bit-free 2 (range 0–16). about the aversive experience of bit-induced pain. The • Most bit-induced behaviours were eminently reversible and improvements cannot be dismissed as ‘merely subjective’. the change was statistically significant (Table 2). The Collectively, the behaviours were predominantly matched pairs t-test gave a P-value of less than 0.005, manifestations of pain experience, expressed by aberrant supporting a causal link between the bit and pain-induced movements of the head, spine and limbs. They ranged from behaviour (Table 3). too little movement (e.g. stiffening, freezing) to too much

TABLE 2: Results for 66 horses switched from bit to bit-free, sorted on number of days bit-free. The number of pain indices when bit-free was signiﬁcantly (P<0.005) reduced in 65 of the 66 horses

# of pain Time bit-free % reduction in pain Case # Age (yrs) BREED Gender USE indices bitted (days) indices bit-free

39 4 TWH G Trail 7 1 86 24 5 Arab/TB F Dressage 23 1 100 15 6 TB G Pleasure 5 1 60 22 6 Arab F Trail 30 1 83 29 23 3/4 TB G Dressage/trail 22 1 100 3 8 WB G Dressage 16 4 62 7 9 TB F Equitation/jumper 39 5 53 32 5 Welsh G Trail/Pony Club 24 7 96 57 8 QH/App G Trail 24 7 96 9 12 WB G Dressage/eventing 6 7 100 44 19 Arab F Trail 32 7 84 35 6 TB F Pleasure/endurance 23 8 87 1 5 TB G Trail 34 14 100 10 7 TB/QH F Pleasure 17 14 35 51 7 cob F Trail 13 14 100 55 8 TB G Pleasure 24 14 96 50 4 App G Jumping/hunter trials 26 19 88 48 4 WB F Dressage 37 20 100 12 6 QH G Western pleasure 24 21 83 27 3 WB F Dressage/eventing 19 30 100 42 7 TB/Trotter G Pleasure 12 30 100 45 7 Arab/Pinto G Dressage/trail 39 30 100 60 9 Paint G Trail 23 30 57 26 10 Gaited G Pleasure 5 30 80 43 10 Arab/QH F Pleasure/dressage 42 30 98 64 12 Arab G Endurance 23 30 100 23 13 QH G Hunter 16 30 0 52 22 TB G Pleasure 23 30 78 5 ? TWH ? Pleasure 21 30 76 56 ? Andalusian G Classical riding 27 30 67 40 6 TB F Pleasure 15 35 100 25 16 App F Pleasure/trail 27 35 100 47 11 Morgan/WB F Dressage 29 40 100 49 12 cob G Jumping, dressage 21 42 90 13 14 TB G Dressage/pleasure 23 42 33 59 3 Draft/X F School horse 7 60 71 58 6 Draft F Trail 21 60 62 4 8 TWH G Trail 11 60 100 53 8 TB G Dressage/jumper 42 60 100 16 15 App G Dressage 43 60 93 31 ? TB F Dressage/trail 13 60 54 8 4 TB G Dressage/eventing 34 64 97 11 11 SDB G Pleasure/trail 24 64 77 2 11 Arab G Dressage/trail 31 72 94 28 5 TB F Dressage/eventing 10 90 70 18 7 WB F Dressage 29 90 100 17 8 WB G Dressage 29 90 100 19 9 WB G Dressage 27 90 100 62 11 Draft G Mounted patrol 9 90 35 63 18 WB F Dressage/jumping 34 90 97 34 8 TB/Paint G Eventing/pleasure 23 120 74 46 8 Arab F Pleasure/endurance 28 120 100 54 11 TB G Trail/ dressage 23 120 69 41 14 Saddlebred G Dressage/jumping 42 150 90 20 12 Arab/Pinto G Trail 18 180 83 65 14 TWH M Dressage/pleasure 28 180 89 6 22 Arab F Trail 12 180 83 61 3 Draft G Mounted patrol 17 240 87 14 13 TB/WB F Dressage/eventing 9 240 100 37 6 TB (OTTB) F Dressage 32 300 75 30 11 WB G Pleasure/trail 7 300 86 38 24 Arab/Welsh G Eventing/trail 43 330 93

TABLE 2: Continued

# of pain Time bit-free % reduction in pain Case # Age (yrs) BREED Gender USE indices bitted (days) indices bit-free

21 10 Arab G Dressage/pleasure 21 365 67 36 10 TB/Conn F Dressage/eventing 51 720 85 33 8 TB/Paint G Dressage/jumping/trail 42 730 93 23 TWH F Trail 24 1095 100

App = Appaloosa; Conn = Connemara; QH = Quarter Horse; STB = Standardbred; TWH = Tennessee Walking Horse; TB = Thoroughbred; WB = Warmblood.

TABLE 3: Results of the matched pairs t-test for means and motion in three planes; i.e. proprioception. Head proprioception controls not only movement and posture of the Bitted Bitless head but also dominates that of the trunk and limbs Mean 23.86 3.15 (Sherrington 1907). In the ridden horse, imbalance can result in Standard deviation 10.88 3.99 a fall with potentially fatal consequences. Head Observations 66 66 proprioception constitutes a central balancing mechanism Actual mean difference 20.71 and is key to a horse’s agility and athleticism. Painful restraint of Hypothesised mean difference 0 the head by a bitted rein interferes with a horse’s ability to Degrees of freedom 65 balance. As a horse’s head movement is synchronised with t Stat 14.50144 limb movement for energy economy in the work of breathing Two-tailed P-value 4.75E-22 and locomotion, proprioception unfettered by nociception is t critical two-tail 1.997138 crucial. A bit also obstructs breathing and probably triggers the The test was significant (P<0.005). negative affective experiences of breathlessness, i.e. respiratory effort, air hunger and chest tightness (Mellor and movement (e.g. bucking, bolting). That some horses may Beausoleil 2017). These unpleasant physical and emotional exhibit a few aversions to the bit is widely acknowledged. consequences of bit pain are also antithetical to athleticism. That every horse is programmed to be averse to the bit and Thus, the bit represents an impediment to welfare, safety and that aversions are numerous is not. The current study showed performance. Noxious stimuli from the bit are proposed to be that at least 65 of 66 horses exhibited aversion to the bit and incompatible with the unimpeded function of at least four that horses have not less than 69 ways of exhibiting systems critical to performance: the nervous, musculoskeletal, frustration, attempts to cope and efforts to avoid bit contact. proprioceptive and respiratory systems. In a review of poor performance, 48 (72%) of these same Dyson et al. (2018) observe that, since 2013 “there is an behaviours were recognisable among 67 behavioural signs of increasing awareness that horses can exhibit lameness when pain compiled by Dyson (2016). Clearly, even though both ridden, while appearing sound when trotted in hand”.In lists are incomplete, the mandible and tongue (a sense common usage, the word ‘lame’ denotes a gait abnormality organ in its own right) figure prominently as the seat of caused by pain in a limb. Another sense of the word is not musculoskeletal manifestations of pain experience in the limited to limbs and carries the wider meaning of ‘disabled, bitted horse. To this must be added pain from the lips, a imperfect and lacking in smoothness’ (Webster). In this sense, particularly sensitive area of another sense organ – skin. at least 65 of the 66 horses when bitted were shown to be A bit stimulates nociceptors mediated by the trigeminal ‘disabled’. When trotted-up in a halter, they were not limb- nerve in lips, tongue, teeth and bone. Gingiva is periosteum, lame, but when bitted and ridden they developed an the most sensitive part of bone. A principle of saddle-fitting is abundance of gait abnormalities. The term ‘bit lame’ is that saddles should not press on bone. A bit breaches this proposed to describe a syndrome of bit-induced disability, i.e. principle. In the male horse, the peridontium of the canine the 69 pain indices here studied. As bit usage is the norm in tooth roots lies immediately ventral to the dorsal edge of the ‘English’ equitation and still frequent in ‘Western’ equitation, it so-called ‘interdental’ space. In the female, unerupted, seems likely that bit lameness will be found to be common in vestigial canine teeth are common (Sisson and Grossman the ridden horse. 1938). In both sexes, ‘wolf’ teeth (erupted and unerupted) A provisional diagnosis of ‘bit lameness’ is testable. If, by may be present in this space. In cross-section, bits are circular removing the bit, a gait abnormality is corrected this confirms and make point contact with the ‘knife edge’ of bone at the a diagnosis of bit lameness and differentiates it from primary ‘bars’. This can be assumed to cause a horse pain, just as it limb and thoraco-lumbar-sacral lameness or the causes us pain if we press the barrel of a pencil sideways into incoordination of equine protozoal myeloencephalitis (EPM). our gums. When the edges of the tongue are pinched As the definitive diagnosis of EPM and other subtle gait between bit and bone, this too is likely to be painful. Pain is abnormalities can be difficult, removal of the bit is also likely when lips are stretched longitudinally to twice their recommended as an early step in the differential diagnosis of normal length by the bit’s retractor effect. Finally, cuts at the lameness and the evaluation of poor performance. Such a commissures will cause pain. step is especially indicated to help interpret the findings of In common with other mammals, the vestibular labyrinths computerised gait analysis, a diagnostic methodology that and receptors in skin, muscle, tendon and temperomandibular has introduced a dilemma over defining the term ‘lameness’ joints of the horse’s head mediate perception of orientation (Van Weeren et al. 2017).

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22nd Annual Resort Symposium ARUBA January 23-25, 2020 The Ritz-Carlton | Palm Beach, Aruba

At the AAEP’s 22nd Annual Resort Symposium, you’ll lower your stress amid Aruba’s natural splendor and raise the level of care you provide to client horses during practical half-day sessions devoted to:

Field procedures and emergencies with Dr. Stephanie Caston Effective sedation and restraint techniques with Dr. John Hubbell Preventative medicine and biosecurity strategies with Dr. Tracy Norman

RACE-approved CE credits: 15