THE CLINICIAN SUMMER 2018

NORTHEAST ASSOCIATION OF EQUINE PRACTIONERS

PRINCIPLES OF HORSE SHOEING

LOWER RESPIRATORY TRACT HEALTH…

EQUINE GASTRIC ULCER SYNDROME (1ST ARTICLE)

PREVENTING AND MANAGING OUTBREAKS…

MANAGING DYSTOCIA AND PREGNANCY….

MAKING REHAB REAL….

IMAGING THE AXIAL SKELETON

ENHANCING YOUR RADIOGRAPHIC TECHNIQUE

OTHER LESSONS LEARNED - IS SCINTIGRAPHY STILL ALIVE?

Summer 2018 www.the neap.com

The Clinician 1 for the Welcome Reception to celebrate the opening of the 10th Annual NEAEP Symposium “From Our Practice to Yours” Wednesday September 26th, 2018 beginning at 7:00 pm at the National Museum of Racing and Hall of Fame 191 Union Ave, Saratoga Springs NY 12866 (Shuttle transportation will be provided from the Holiday Inn) THE CLINICIAN SUMMER 2018

Volume 8, Number 2 Summer 2018

2018 Executive Committee Board Of Directors Veterinary Industry Council Rep Carli Progin MS President Sarah Cohen, DVM Territory Manager, Travis Blackwelder DVM MS Miller and Associates Boehringer Ingelheim Animal Health Statesville Equine Clinic Ronald B. Gaeta, DVM Vice President Dunbarton Equine Executive Director/CEO Raul J. Bras DVM, CJF, APF David G. Dawson Michele MacRae Podiatry Department Rood and Riddle Michele MacRae Farrier Services Equine Hospital Stuart Muir, CJF Treasurer Podiatry Department Rood & Riddle Jim Zeliff, DVM Equine Hospital Allegheny Equine Associates Christopher Penola, APF Past-President Robert Causey, DVM, Ph.D. Christopher Penola Farrier Services Department of Animal and Gregory S. Staller, DVM VeterinarySciences Running ‘S’ Equine Veterinary Services University of Maine contents

6 Principles Of Horse Shoeing 12 Lower Respiratory Tract Health 16 Equine Gastric Ulcer Syndrome (1St Article) 20 Preventing And Managing Outbreaks 30 Managing Dystocia And Pregnancy 34 Making Rehab Real 36 Imaging The Axial Skeleton 39 Enhancing Your Radiographic Technique 42 Other Lessons Learned - Is Scintigraphy Still Alive?

The Clinician 3 THE CLINICIAN SUMMER 2018

President’s Letter Dear Friends,

It is my pleasure to be able to invite you to join us in Saratoga Springs, NY in September for our 10th Annual Symposium - From Our Practice to Yours. Having recently toured the town of Saratoga Springs and the facilities we will be utilizing, I can say with complete confidence that you will not be disappointed! Saratoga Springs is a beautiful place to visit, and the variety of restaurants, spas and shopping is astounding for a small town. The downtown is vivid, and is quite walkable from the hotels in the area, and just a short cab ride from the outlying hotels. Please consider booking an extra day to enjoy the town and all of its amenities.

The Program Committee Chairs have assembled an all star line up of speakers from around the world to provide only the highest quality of continuing education available in both the classroom and wet lab settings. New this year we will be offering daily combined sessions to allow veterinarians and farriers to exchange ideas and information on certain topics, as well as various engaging topics specific to our lameness, podiatry, internal medicine and reproduction programs.

I look forward to welcoming you to the Annual Symposium in person at our Welcome Reception at the National Museum of Racing and Hall of Fame. The board and myself are incredibly excited for this year’s Symposium and we hope you are too!

See you in September, Dr. Travis Blackwelder President

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Principles of Horse Shoeing - Doug Butler My Experience with Horse Foot Balance ©2017 Doug Butler PhD, CJF, FWCF Butler Professional Farrier School

All competent farriers can recognize balance or lack thereof in This is different for each gait. Using a force plate, Bartel and the horse’s foot. It has been my experience in 50 years of teaching Schryver (1978) showed that the foot lands toe first at the walk, flat that those persons who say balance is controversial or subjective at the trot, and heel first at the gallop. Functional balance is have not spent the time to study and/or had enough farrier considered important in performance and speed horses when a experience to understand balance. Seeing and achieving balance is a conformation defect causes limb interference or lameness. Lung- right brain activity learned by experience until it almost becomes witz (1884 – translated in 1898) showed the relationship between subconscious. conformation and gait. Balance as applied to farrier work is defined as equal weight or The three-dimensional views of the feet standing and in force distribution around the center of gravity of the horse’s limb. motion were first recognized by Goubaux and Barrier (1884 – Balance is three-dimensional. In the ideal horse, the center of gravity translated in 1892). Muybridge (1887) published photographs of the foot and the limb above it are identical. However, ideal horses showing the sequence of horse movement in two-dimensions, but exist only to compare to and describe those who are not. it wasn’t until recently that the movements of the foot were filmed, Balance implies equilibrium. The horse’s foot functions as an described and named by Fredrickson and Drevemo (1972). equalizer of the three-dimensional weight bearing forces exerted I, Butler (1992), used these three-dimensional views to describe between the horse and the ground. The laminae transfer vertical balance in my FWCF Thesis. forces to horizontal forces on the coffin bone (third phalanx). X-Balance. When the foot is viewed from in front (or the rear When the forces are not uniform, the blood supply is compromised when the foot is picked up), the center of gravity or plumb line of and remodeling of the bone according to Wolff’s Law (1898) and the limb of the ideal that we compare others to drops from the hoof distortion result. point of the shoulder to bisect the extensor process of coffin bone Balancing involves trimming the hoof and fitting the shoe. (the distal phalanx) and hoof base. When viewed from the rear, the Perfect balance is rarely achieved, but the closer we get to it the plumb line drops from the point of the buttocks bisecting the hoof better chance we have for maximizing performance and sustaining base. The axis of the pastern is perpendicular to the base of the soundness in the horse. coffin bone. This view is referred to as medial-lateral or X-balance. The sides of the hoof may need to be dressed (shaped with a rasp) There are two aspects to balance: to be made parallel to the sides of the coffin bone. 1. Geometric, or static balance, refers to plumb lines positioned Y-Balance. When the foot is viewed from the hoof bottom (or on limbs in the standing position. Consideration of geometric from above), the plumb line is identified by a point about 3/8 to ¾ balance only is sufficient for most sound horses. The joints of the inch (1 centimeter) behind the point of the trimmed frog. This lower leg are designed to accommodate uneven ground surfaces point is often called Duckett’s Dot (1990). It is directly below the and minor conformation defects. Function follows form. Therefore, center of the attachments of the extensor and flexor tendons on the geometric balance should always be considered first. coffin bone. A plumb line representing the center of gravity of the It may be all that is necessary on most horses. limb passes through this point. Farriers find this point useful in 2. Functional, or dynamic balance, refers to limb movement dressing and symmetrically shaping a distorted hoof and judging and foot placement on the ground. the fit of a shoe. This view is referred to as hoof form or Ybalance.

6 www.theneaep.com 585-205-5122 Principles of Horse Shoeing - Doug Butler From Our Practice to Yours My Experience with Horse Foot Balance ©2017 Doug Butler PhD, CJF, FWCF Butler Professional Farrier School 10th Annual NEAEP Symposium September 26th - 29th 2018

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Ideally, more hoof base should be behind the dot than in front Balance is influenced by many things. First and foremost is of it. limb conformation. Nutrition, condition of the teeth, ability and Z-Balance. When the foot is viewed from the side, the center position of the rider, soreness, draft, speed, weight and configura- of gravity or plumb line drops from the center of the scapula tion of the shoe, can all affect balance. through the joint space behind the extensor process and bisects the Each time a horse is trimmed and shod, the farrier should feel hoof base. The center of the scapula is the mid-point of suspension challenged to come closer to the ideal stance and gait for that of the front limb by the serratus ventralis muscle. In the hind limb, particular animal. At the same time, the farrier must the place the the plumb line drops from the center of the hip joint (acetabulum) minimum amount of stress on the limb. The object is to sustain bisecting the hoof base. This view is referred to as Z-balance. Colles soundness or return to it if the horse is lame. (1983) found the base of the distal phalanx forms an angle between The hoof grows symmetrically when weight is distributed 5 and 10 degrees with the hoof base. equally over it. Shoe wear and hoof form give us clues to shoe Toe or heel should be trimmed away until the upper one-third fitting as well as hoof trimming and dressing. Radiographs can of the hoof is parallel to the axis of the pastern. Distorted hoof determine if joint spaces are parallel and unstressed. should be dressed parallel to the dorsal surface of the coffin bone. Dollar (1898) recommended moving the shoe toward the side Hoof shape mirrors bone shape (Allen, 1993). that wears the most until the shoe will wear evenly on sound horses. Functional balance, which describes the position of the foot in Russell (1907) recommended trimming the foot so it strikes the movement, can be compared to the movements of an airplane. Roll ground flat on lame horses. Gamgee (1871) recommended ‘sculp- is X-balance or footfall, Yaw is Y-balance or stride arc, and Pitch is turing’ (dressing) the hoof making its form parallel with the dorsal Z-balance or animation. surface of the underling coffin bone.

8 www.theneaep.com 585-205-5122 THE CLINICIAN SUMMER 2018

Visualizing the position of the coffin bone within the hoof Clayton HM. The effect of an acute angulation of the hind hooves around its axes is essential to creating a sculptured hoof attached to on diagonal synchrony of trotting horses. Exercise Physiology. p. a shoe base of support. The shoe must be fit to provide the base 91-94. necessary to bring the limb into equilibrium. Clayton HM, Sigafoos R, Curle RD. Effect of three shoe types on It takes many hours, even years of experience to learn to ride a the duration of breakover in sound trotting horses. Equine Sports horse in balance. An expert rider seems to flow in unison with the Medicine 1990;(Mar/Apr):129-132. horse. Learning to balance a horse’s stance and gait also requires Clayton HM. Comparison of stride kinematics of the collected, extensive practice and experience. An expert farrier will consciously, medium, and extended walks in horses. Amer J Vet Res 1995;56:849- even unconsciously, blend the elements of balance to obtain 852. equilibrium of stance and gait. Daniels BB. Understanding wear patterns on horseshoes. Hoof Care and Lameness 1996;66(1):14-20. References Dollar JAW. A Handbook of Horseshoeing. David Douglas, Allen NT. The effect of geometric mediolateral hoof balance on Edinburgh, Scotland 1898. the distal phalanx and hoof capsule in equines. Foot- Colles CM. Interpreting radiographs: the foot. Equine Vet J notes1993;2(3):25. 1983;15:297. Allen NT. Geometric mediolateral hoof balance on the distal Duckett DH. The assessment of hoof symmetry and applied phalanx and hoof capsule in equines. MS Thesis: Colorado State practical shoeing by use of external reference points of the equine hoof. University, 1993. International Farriery and Lameness Seminar. Newmarket, England Balch OK, Clayton HM, Lanovaz J. Effects of increasing hoof 1990. length on limb kinematics of trotting horses. Proc Amer Assoc Equine Firth EC, Schamhardt HC, Hartman HC. Measurements of Pract 1994;40:43. bone strain in foals with altered foot balance. Amer J Vet Res Balch OK, Ratzlaff MH, Hyde ML, White KK. Locomotor effects 1988;49(2):261-265. of hoof angle and medio lateral balance of horses exercising on a high Fredrickson I, Drevemo S. Equine joint kinematics and co-ordi- speed treadmill: preliminary results. Proc Amer Assoc Equine Pract nation. ACTA Vet Scand 1972; (suppl. 37):3-43. 1991;37: 687-705. Gamgee J. A Treatise on Horseshoeing and Lameness. Longmans, Balch OK, White KK Butler KD. Review article: Factors involved Green and Co., London, England 1871. in the balancing of equine hooves. J Am Vet Med Assoc 1991;11: Gates A. Shoeing the Thoroughbred racehorse. Amer Farriers J 1980-1989. 1987;(July/Aug):37-51. Barrey E. Investigation of the vertical hoof force distribution in Gonzales AZ. Proper Balance Movement: A Diary of Lameness. the equine fore limb with an instrumented horseboot. Equine Vet J REF Publishing, Manassas, VA 1986. 1990; (suppl.9):35-38. Gonzales T. Rider induced lameness and its effect on concussion Bartel DL, Schryver HF, Lowe JE, Parker RA. Locomotion in the and lameness. Anvil 1986; (June):18-20. horse: a procedure for computing the internal forces in the digit. Amer Goubaux A, Barrier G. The Exterior of the Horse. Lippincott, J Vet Res 1978;39(11):1721-1727. Philadelphia 1884. Transl. S Harger 1892. Bumbaugh S. Buzzwords and brainstorms to decode Duckett’s Jordon R. The Gait of the American Trotter and Pacer. William Dot. Hoofcare and Lameness 1992;3:24-26. R. Jenkins Co., New York 1910. Butler KD. Factors affecting hoof balance. FWCF Thesis: Jurga F. Diagonal imbalance. Hoofcare and Lameness. Worshipful Company of Farriers, London, England 1992. 1993;(Fall-Winter):13-14. Butler KD. Shoeing In Your Right Mind. Doug Butler Enterpris- Kobluk CN, Robinson RA, Gordon BJ, Clanton CJ, Trent AM, es, Crawford, NE 1998. Ames TR. The effect of conformation and shoeing: a cohort study of Butler KD. What every equine practitioner should know about 95 Thoroughbred racehorses. Proc Amer Assoc Equine Pract hoof balance. Proc Amer Assoc Equine Pract 1994;40:133-134. 1989;35:259. Clayton HM. The effect of an acute hoof wall angulation on the Leach D. Biomechanics of limb weight bearing. Equine Lameness stride kinematics of trotting horses. Equine Vet J 1990;9 (sup- and Foot Conditions. Post Graduate Committee, University of pl.9):86-90. Sydney Australia 1990;130:59-69.

The Clinician 9 THE CLINICIAN SUMMER 2018

Lungwitz A. A Textbook of Horseshoeing. Lippincott, Philadel- Taylor DD. Spacial Relationships of the Distal Phalanx and phia 1884. Transl. JW Adams 1898. Navicular Bone in the Equine Foot. MS Thesis: Colorado State McLellan CA. The Art of Shoeing and Balancing the Trotter. The University, Fort Collins 1995. Trotter and Pacer, New York 1927. Turner TA. Navicular disease management: shoeing principles. Muybridge E. Animal Locomotion in Animals in Motion. 1887. Proc Amer Assoc Equine Pract 1986;32:625. Dover Publications, New York 1957. Turner TA. The use of hoof measurements for the objective Parker RA. The Analysis of the Forces and Displacements in the assessment of hoof balance. Proc Amer Assoc Equine Pract Digit of the Horse During the Walk. MS Thesis: Cornell University, 1992;38:389. Ithaca, NY 1973. Williams G. Measuring the effect of forces on the equine foot. The Russell W. Scientific Horseshoeing. 10th Ed. CJ Krehbiel and Co., Forge. Stoneleigh, England 1996;Aug: 7-9. Cincinnati, OH 1907. Wolff J. Pas Destez der Transformation der Knochen. Hirschwald, Schryver HF, Bartel DL, Langrana N, et. al.. Locomotion in the Berlin, Germany 1892. horse: kinematics and external and internal forces in the normal equine digit in the walk and trot. Am J Vet Res 1978;39:1728-1733. Simpson JS. The Mechanics of Horseshoeing Simplified. (2nd ed.). Last Chance Ranch Enterprises, Walla Walla, WA 1993. Snow VE, Birdsall DP. Specific parameters used to evaluate hoof balance and support. Proc Amer Assoc Equine Pract 1990;36:299- 311. Taylor D. Spatial relationships of the distal phalanx and navicu- lar bone in the equine foot. Footnotes 1993;2(4):33.

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Lower Respiratory Tract Health In The Equine Athlete: Respiratory Health For Maximum Performance Emmanuelle van Erck - Westergren, DVM, PhD, Dipl. ECEIM Equine Sports Medicine Practice, Belgium

Whatever the equestrian discipline, age or breed, and even in The importance of the aerobic pathway in the muscular the absence of disease, the respiratory system represents the main energetic supply, whatever the discipline, is well recognized in limiting factor to exercise in the horse. Respiratory diseases are the horses. Racehorses are probably mainly limited by the oxygen second most common cause of wastage in sport horses and supply at the muscle level. Indeed, despite a large pulmonary racehorses. This is due to a number of risk factors naturally present exchange area, a dramatic increase in pulmonary ventilation, an in the horses’ daily environment. Respiratory diseases may evolve increase in cardiac output and packed cell volume, horses exercising subclinically but still impede performance. Proper diagnosis is at intensities higher than 60% of VO2max become hypoxemic, and therefore essential. Upper airway endoscopy and lower airway even hypercapnic (Bayly et al, 1983). sampling are important complementary exams. Numerous researches have shown that horses have a high muscle mass with enormous metabolic requirements resulting in 1. Some elements of physiology O2 uptake and CO2 production that exceed the ventilation Oxygen transport from the ambient air to the exchange zones capacities, especially in well trained horses. These observations in the lung, then from the exchanging zone into the mitochondria, indicate that the respiratory system may be the ultimate limiting is achieved by the coordinate action of the respiratory and cardio- factor to high intensity exercise in horses. vascular systems. During exercise, the increase in the metabolic Some anatomic and physiologic peculiarities in horses may rates imposes an increased load on all physiological steps involved explain the fact that respiration is the weak link in the oxygen chain. in what is called the oxygen chain: increase in minute ventilation (1) Length, section and shape of the upper airway contribute to a and in alveolar ventilation, diffusion, cardiac output and oxy- high anatomical dead-space, and associated to the compulsory gen-carrying capacity (splenic contraction) and muscles blood nasal breathing, result in an increased resistance to airflow and distribution. The efficiency of the links of this chain may be energetic cost of breathing, which probably “downregulate” the modified by training or illness. The soundness and capacity of increase in pulmonary ventilation during intense exercise. (2) these systems will therefore play a substantial role in determining Mixed venous blood coming back from the peripheral tissues the performance potential of a horse, whatever the equestrian (muscles) has a partial pressure in O2 as low as 15 mmHg, which is discipline he is involved in. A limitation in of one of the chain links in relation to the dramatic O2 removal by the working muscles. (3) will limit the efficiency of the entire chain and may result in poor Impairment of gas diffusion at the level of the alveolo-capillary performance. membrane because of the dramatic increase of cardiac output Training or conditioning is a chronic repetition of exercise that reduces the time for gas exchange. A relative impairment of the induces physiologic and morphologic adaptations in horses. Some ventilation/perfusion ratio has been also suggested as a possible tissues or function are malleable and show a response to training reason for the gas exchange impairment. (muscles, cardiac function) but other remained unchanged (lung and respiratory function). Because the respiratory system is not 2. Epidemiology of respiratory problems anatomically enlarged nor functionally improved by training, Studies performed on small group of racing horses (Couëtil it is likely to become the limiting factor to performance in well- and Denicola, 1999; van Erck et al, 2006), in which cytologic trained animals. examination of BAL was included in the string of tests examining

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causes of poor performance reported the major incidence of lower causes metabolic and hormonal alterations which disturb immuni- airway subclinical problems (including Inflammatory Airway ty (Jaenseen-Waeren et al., 1999 ; Art et al., 2006). A decreased Disease-IAD-, Recurrent Airway Obstruction-RAO-, Exercise-In- immunity has been suggested as a predisposing factor to infectious duced Pulmonary Hemorrhage-EIPH) on exercise tolerance. airway problems in these horses (Tyler et al., 1996; Robson et al., In a retrospective study of our cases of poor performance, the 2003). Depression of the immune system and the occurrence of distribution of the disciplines represented was different from the repeated inflammatory and oxidative processes during training and aforementioned studies: 50% of the horses were jumping horses. competitions seem to create favorable conditions to the outbreak of These horses were examined at rest (clinical examination biochem- respiratory diseases in endurance horses. These respiratory istry, arterial blood gases, pulmonary function test, endoscopy), problems are often subclinical but have an impact on performance during exercise (heart rate, lactate and endoscopy) and after and may impede the pursuit of their physical preparation as well as exercise (echocardiography, lower airway endoscopy and BAL, post-race short and long term recovery. These findings highlight biochemistry). A diagnostic of lower respiratory problem was done the importance of proper environmental management and regular in 54 % of the cases. The incidence of lower airway disease is high vaccination. in Warmblood sport horses and is, even in this type of horses, the For the practitioner, the diagnosis of subclinical lower airway main reason for exercise intolerance or poor performance. diseases is difficult without ancillary examinations. Most horses The lack of adaptation to training and the high prevalence of with chronic IAD typically do not show respiratory symptoms such respiratory disease explain the important role of this system in the as cough or nasal discharge but display more subtle signs such as occurrence of exercise intolerance. The foal is born with its premature fatigue during exercise, prolonged recovery or decreased intrinsic respiratory capability and the only event that may happen energy during competitions. Tracheal endoscopy is useful to later is a decrease in its respiratory capability, for multiple reasons: evaluate the amount of mucus or even blood present in the lower housing in dusty environment and feeding with dry food, training, airways. Post-exercise endoscopy is often more relevant. A signifi- transportation, mingling during competition, all factors that favor cant correlation has been shown between the presence of tracheal the development of infectious, inflammatory and allergic diseases. mucus and poor performance is racehorses (Holcombe et al. 2006). Although the resistance of the lower airway account for only 20% In showhorses, although IAD does not seem to affect performance of the total pulmonary resistance in healthy horses, when their (Gerber et al. 2003), it has been associated to decreased willingness lumen is narrowed by functional (mucus hypersecretion, broncho- to perform (Widmer et al. 2009). This is in accordance with our spasm), infectious (mucopus), or other problems (pulmonary findings, where lower airway inflammation, including inflammato- hemorrhage, oedema, dynamic collapse), their resistance increases ry airway disease (IAD), is shown to be detrimental to upper airway and become a factor limiting ventilation. stability and may accelerate the onset of fatigue (Fraipont et al., 2008, Richard et al., 2009). 3. Lower airway issues Definitive diagnosis of lower airway disease can be established Whatever the type of respiratory disease diagnosed, it may through airway sampling. Tracheal washes are mostly useful to cause a significant decrease in athletic parameters and delayed diagnose infectious diseases whereas broncho-alveolar lavage are cardio-respiratory recovery. Several factors promote the occurrence indicated in cases of chronic problems such as IAD, RAO or EIPH. of inflammatory diseases, such as age (higher prevalence in older Cytologic analysis allows evaluating the severity of the disease individuals) and environmental conditions. In Europe, horses are process, evaluating environmental quality and of course orientating often kept indoors in ‘traditional’ environments, characterized by adequate therapy. older buildings containing rows of boxes with limited ventilation, Evaluating the functional repercussions of a disease may also indoor storage of hay and straw, closed doors and windows during be indicated if permanent pathological sequelae are suspected. autumn and winter. This type of management encourages chronic There are currently readily applicable and commercially available respiratory inflammation (Robinson et al. 2006). Intensive non invasive respiratory function tests. Impulse oscillometry may training, repeated transports and mingling during competitions be developed for application in a near future. may also promote the development and transmission of infectious Prevention remains a guarantee for the maintenance of lower diseases. airway health. A dust-free and hygienic environment both at home The quality of environmental management is not the only and on shows limits risks of lower airway inflammation. explanation to the emergence of lower airway diseases in horses: competition itself is also a key factor. Endurance competition

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Equine Gastric Ulcer Disease: The Nitty Gritty! Frank M. Andrews, DVM, MS, Diplomate ACVIM LVMA Equine Committee Professor and Director Equine Health Studies Program, Department of Veterinary Clinical Sciences School of Veterinary Medicine, Louisiana State University

TAKE-HOME MESSAGE and correcting of the underlying cause, environmental manage- Equine gastric ulcer syndrome (EGUS) is common in perfor- ment, dietary manipulation and pharmacologic intervention. These mance horses. Diagnosis of EGUS is based on history, clinical signs, proceedings focus on a comprehensive approach to treatment of endoscopic examination, and response to treatment. All ages and EGUS and briefly cover basic anatomy and physiology of the breeds of horses are susceptible to EGUS and current therapeutic equine stomach, multiple etiologies and risk factors for EGUS, and strategies focus on blocking gastric acid secretion and raising preventative management strategies. stomach pH. One FDA-approved drug exists to treat (GastroGard®) The proximal third of the equine stomach is lined with and one drug exists to prevent (Ulcergard® Merial LTD, Decatur, non-glandular stratified squamous epithelium, an extension of the GA) gastric ulcers in horses in the USA. However, a more compre- esophagus. The majority (80%) of ulcers are found in this region. hensive approach to EGUS includes determining and correcting of The distal two-thirds of the stomach is covered by glandular the underlying cause, environmental management, dietary manipu- mucosa, which is responsible for secretion of mucus, hydrochloric lation and pharmacologic intervention. Several feed supplements acid (HCl) and Pepsinogen. Ulcer development in these regions is have been shown to improve stomach health after successful thought to be an imbalance between protective and aggressive treatment of EGUS. factors (Table 1). The nonglandular squamous mucosa is predis- posed to acid injury because it lacks the protective and buffering capacity provided by the bicarbonate-rich mucus found in the INTRODUCTION glandular region. The glandular region, on the other hand, has Equine gastric ulcer syndrome (EGUS) is common in perfor- extensive protective mechanisms, including a bicarbonate-rich mance horses and in foals. Diagnosis of EGUS is based on history, mucus layer, an extensive capillary network, and rapid restitution of clinical signs, endoscopic examination, and response to treatment. epithelium when injured. Ulcers in this region are less common and All ages and breeds of horses are susceptible to EGUS and current heal rapidly. However, recently resistant glandular ulcers have been therapeutic strategies focus on blocking gastric acid secretion and reported in horses and longer treatment periods may be necessary raising stomach pH. One approved drug exists to treat EGUS in to heal these ulcers. USA and that is GastroGard® (Merial LTD, Decatur, GA). However, a more comprehensive approach to EGUS includes determining

TABLE 1: PHYSIOLOGIC FACTORS AFFECTING ULCER DEVELOPMENT AGGRESIVE FACTORS PROTECTIVE FACTORS NON-GLANDULAR MUCOSA GLANDULAR MUCOSA Hydrochloric acid secretion Epithelial restitution (poor) Epithelial restitution (rapid) Organic acid production (VFAs) Intracellular bicarbonate Bicarbonate-mucus layer Pepsin conversion from Mucosal blood ow, poor Mucosal blood ow, extensive pepsinogen Prostaglandin E production Duodenal reflux of bile acid

16 www.theneaep.com 585-205-5122 THE CLINICIAN SUMMER 2018

TABLE 2: CLINICAL SIGNS AND RISK FACTORS OF EGUS CLINICAL SIGNS ADULTS FOALS RISK FACTORS Acute colic Diarrhea Stress Recurring colic Abdominal pain Transportation Excessive recumbency Restlessness High-grain diet Poor body condition Rolling Stall confinement Partial anorexia Lying in dorsal recumbency Intermittent feeding Poor appetite Excessive salivation Intense exercise Poor performance/training Bruxism Racing Attitude changes Intermittent nursing Illness Stretching often to urinate Poor appetite NSAID use Inadequate energy Management changes Chronic diarrhea.

CAUSES OF EGUS Exercise Intensity Horses are continuous gastric HCl secretors, and acid exposure Horses involved in training and racing are at high risk to is thought to be the primary cause of EGUS. Several acids (HCl, develop EGUS. Current prevalence figures show that 60 to 90% of volatile fatty acids (VFAs), and bile acids) have been shown to cause performance horses have EGUS. It has been shown that abdominal damage to the non-glandular region of the equine stomach. In a pressures increased in horses running on a high-speed treadmill, recent report, HCl alone and in combination with VFAs (acetic, which decreased stomach volume. Contraction of the stomach propionic, butyric and valeric acids) caused inhibition of cellular during exercise allowed acid from the dependent portion of the sodium transport, cell swelling, and eventual ulceration, when stomach to reflux up into the non-glandular mucosa leading to acid exposed to the non-glandular squamous mucosa at pH < 4.0. injury. Daily exercise may increase the exposure of the non-glandu- Ulcerogenic effects of the VFAs in combination with HCl were dose lar mucosa to acids explaining the increased prevalence of gastric dependent and the intensity of damage was correlated to VFA chain ulcers in horses racing and training. Furthermore, serum gastrin length. Bile acids were shown to increase the non-glandular concentration has been shown increase in exercising horses, which mucosal cell permeability to hydrogen ions, which eventually lead might increase HCl secretion. to ulceration. However, the effects of bile acids in EGUS is ques- tionable because they usually come from less acidic duodenal reflux Intermittent vs. Continuous Feeding and are non-ulcerogenic at a pH >4. Pepsinogen, which is cleaved Horses grazing at pasture have a decreased prevalence of to pepsin at a pH<4, might have a role in the development of EGUS. During grazing, there is a continuous flow of saliva and EGUS. This proteolytic digestive enzyme may act synergistically ingesta that buffers stomach acid, keeping stomach pH is > 4 for a with HCl to result in damage to the glandular and nonglandular large portion of the day. On the other hand, when feed is withheld mucosa. While HCl and stomach pH have been incriminated as the from horses, before racing or in managed feeding stables, gastric main culprits causing EGUS, it is likely that a combination of HCl, pH drops rapidly and the non-glandular mucosa is exposed to an organic acids, and pepsin act synergistically to break down the acid environment. Intermittent feeding has been shown to cause protective barriers in the stomach and cause EGUS. and increase the severity of gastric ulcers in horses and an intermit- tent feeding model has been used to consistently produce EGUS. Risk Factors The non-glandular mucosa is the most susceptible to ulceration in While acid injury has been implicated in the cause of EGUS, horses subjected to intermittent feeding due to its lack of mucosal several risk factors have been identified (Table 2). Recently a risk protective factors; however glandular number and severity might calculator was introduced for horse owners to see if their horses are also increase. at risk for gastric ulcers (Table 3). Diet Diet has been implicated as a risk factor for EGUS. Serum gastrin concentrations are high in horses fed high concentrate

The Clinician 17 THE CLINICIAN SUMMER 2018

(grain) diets. Also, high concentrate diets are high in digestible to Thoroughbred racehorse, which may explain the higher preva- carbohydrates (water soluble carbohydrate [WSC]). Water soluble lence of EGUS (93%) in racing and training Thoroughbreds. carbohydrates are fermented by resident bacteria, resulting in the production of VFAs, which in the presence of low stomach pH Stall Confinement (< 4), cause acid damage to the non-glandular squamous mucosa. Horses housed in pastures have a decreased prevalence of Furthermore, two studies in horses fed alfalfa hay with and without gastric ulcers, compared to horses that are housed in stalls. The grain (high protein and calcium) showed higher stomach pH and reason for this may be multifactorial, as horses that are stalled may lower ulcer scores compared to horses fed grass hay (brome grass or be fed intermittently and housed without exposure to other horses. Coastal Bermuda). Thus, feeding alfalfa hay has protective effects on the non-glandular mucosa in horses. Non-Steroidal Anti-Inflammatory Drugs Transport Stress Non-steroidal anti-inflammatory drugs (NSAIDs), phenylbu- Transportation of horses has been associated with dehydration, tazone and flunixin meglumine, have been shown to induce gastric increased threat of respiratory illness (pleuritis, pleuropneumonia), ulcers in horses. However, NSAIDs has not been shown to be a risk and immune suppression. When horses are being transported, factor for EGUS in multiple epidemiologic studies in race horses. In water and feed consumption is usually decreased which may cause one study NSAIDs did cause ulcers in the glandular mucosa and an increased incidence of EGUS. Transportation has been shown to increased the severity of ulcers in the non-glandular squamous increase the severity of gastric ulcers in horses. However, a recent mucosa. NSAIDs are thought to cause more severe ulcers in the endoscopic study in western performance Quarter horses subject to glandular stomach mucosa because of their effect on prostaglandin frequent travel and intensive training had a lower prevalence (40%) inhibition. Prostaglandin inhibition results in decreased mucosal of gastric ulcers than horses in race training, calling into question blood flow, decreased mucus production, and increased HCl the effect of these factors on the development of EGUS in this secretion. While prostaglandins are also important in the regulation group of Quarter Horses. The authors' speculated that demeanor of acid production and sodium transport, it may be their effect on played a role in the lower prevalence of ulcers in these horses. Quar- mucosal blood flow that is the most important. Adequate blood ter horses are calm and do not exercise intensively when compared flow is necessary to remove the hydrogen ions that diffuse through the mucus layer covering the glandular mucosa. Gastric mucosal

TABLE 3: EGUS RISK CALCULATOR FOR HORSE OWNERS (ADAPTED FROM BARAKAT C (2016) GASTRIC ULCER RISK SCORE 1 2 3 4 5 score 1. How many meals is your horse’s grain ration divided into per day? 3 or more 2 1 2. Ho much of the day does your horse spend grazing or eating hay? 75% 50% 75% 3. How many days in a row has your horse been on NSAIDs in the past 3 months? none < 10 days > 10 days 4. Over the past 3 months, which of the following apply to your horse? - Spend 1 day away at a show, clinic or other - Took a trailer ride - Attended competition or clinic at unfamiliar location - Sustained injury or developed illness 5. How many days per week is your horse in intense work? none 1 or 2 > 3 TOTAL: *Risk score: 0-5: Low risk 6-15: Moderate risk 15-25: High risk Barakat c. What’s your horse’s ulcer risk. Equus 2016, 464:68-77

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ischemia may lead to a hypoxia induced cellular acidosis, release of Currently there are no hematologic or biochemical markers to oxygen free radicals, phospholipase, and proteases, which may diagnose EGUS. However, O’Connor et al. recently evaluated the damage the cell membrane leading to necrosis and ulceration. potential of a sucrose absorption test to diagnose gastric ulcers. Helicobacter spp. Sucrose (table sugar) is a disaccharide broken down in the brush While Helicobacter spp. is an important cause of ulcers in border of the intestine to glucose and fructose. If absorbed by the other species, it has not been proven to be a cause of gastric ulcers body, it must be absorbed across damaged gastric mucosa. It is not in horses. Helicobacter-specific DNA was isolated from glandular metabolized by the body, and is excreted in the urine as intact and non-glandular mucosa of horses and a new species of Helico- sucrose. Urine sucrose increased in horses with experimentally bacter, H. equorium, was recently isolated from the feces of horses induced gastric ulcers. Initial evaluation of this test suggested that it and foals. The importance of this discovery is unknown and the holds promise to diagnosis EGUS, without the expense and role of Helicobacter spp. in EGUS remains speculative, in light of expertise of gastroscopy, but more research is needed to further several reports in which Helicobacter spp. were not seen in necrop- refine this technique. Also, sucrose can only be measured by HPLC, sy specimens from the stomach of horses with EGUS. However, which is expensive. colonization of gastric ulcers by resident stomach bacteria (E. coli, Because of the lack of any additional laboratory diagnosis, in etc.) may inhibit healing and studies have shown that treatment situations where ulcers are strongly suspected, but gastroscopy is with probiotics (lactobacillus spp.), antibiotics (SMZ), and antacids not available, it may be worthwhile to start empirical treatment and may facilitate healing of spontaneously occurring nonglandular observe for resolution of clinical signs. If the horse does not gastric ulcers in horses and other species. This might be true in respond to treatment, referral to a facility with a gastroscope is indi- horses with chronic non-responsive gastric ulcers. cated. This is especially recommended if a trial period of treatment does not alleviate clinical signs in a few days. CLINICAL SIGNS Clinical signs associated with EGUS are numerous, and often vague. Ulcers are more common in horses showing clinical signs (Table 2). In Thoroughbred horses in race training, gastric ulcers were associated with poor performance, poor hair coat, partial anorexia (picky eating), and colic. Of horses with a client com- Your time is best spent caring for your plaint of conditions associated with gastric ulcers, or showing patients, so we spend ours making subtle signs of poor health, gastric ulcers were identified in 88-92% the whole process easier, from compared to 37-52% identified in horses’ not showing clinical ordering to administration. signs. In addition to an increased prevalence of ulcers in clinically affected horses, the severity of ulceration may be correlated with the At Order.WedgewoodPetRx.com, severity of the symptoms. you have access to: • An easy medication search • A list of favorites that YOU DIAGNOSIS control While an appreciation of the basic anatomy and physiology of • Quick reordering from order acid production is important, it is equally important to be able to history identify horses which would benefit from anti-ulcer therapy (Figure • A price specials page 1). Gastroscopy is the only definitive diagnosis of gastric ulcers Trish, Account Manager, currently available. The procedure for gastroscopy has been with Warrick and Dunkin described in detail elsewhere, but requires at least a 2 meter endoscope to visualize the non-glandular mucosa and Margo plicatus and a 2.5m to 3m to visualize the pylorus and proximal duodenum in most adult horses. Once visualized, ulcers should be Create your free account today at scored for severity. Use of a scoring system allows the clinician to ORDER.WEDGEWOODPETRX.COM monitoring healing and evaluate efficacy of treatment.

The Clinician 19 THE CLINICIAN SUMMER 2018 NEAEP

Preventing and Managing Outbreaks of Infectious Diseases on the Breeding Farm Claire Card DVM PhD diplomate ACT Dept LACS, Western College of Veterinary Medicine University of Saskatchewan

Infectious diseases outbreaks on breeding farms are important CURRENT INDUSTRY PRACTICES causes of economic loss, and may harm the reputation of the farm There are a large number of mares bred on farms with: live and the business operation. Biosecurity practices are key to the cover, pasture breeding, fresh semen artificial insemination, cooled prevention of infectious diseases on breeding farms. However, transported semen and frozen semen. Gametes, particularly sperm disease outbreaks are not always preventable. Diseases may spread are routinely collected and shipped from stallions. Cooled and because of: direct horse to horse contact, aerosol transmission, cryopreserved embryos and semen may move between countries. ingestion, fomites, ticks/biting insects, venereal means, and assisted International horse movement and gamete shipments provide reproductive technologies. Horses maintained under good manage- opportunities for rapid dissemination of pathogens both within ment that have regular deworming, dental care, and core and risk and between countries. based vaccination are less likely to experience morbidity from Zoosanitary regulations are typically instituted by government infectious diseases. bodies that wish to minimize the risk of domestic disease spread, by Prevention and Management of Infectious Diseases is often regulating importation, or exportation of horses to avoid the based on Biosecurity Guidelines. Examples of Biosecurity Guide- introduction or spread of venereal pathogens. This may vary by lines include the Infectious Disease Outbreak Guidelines of the state or country and may change year to year, therefore it is prudent AAEP which may be found at https://membership.aaep.org/ to check the current regulations prior to each breeding season. iMISprod/AAEP/Sign_In.aspx?ReturnURL=/imisprod/securecon- This document on the Biosecurity Guidelines for the Equine tentsso/drupalsso.aspx al also the AAEP has guidelines on preven- Breeding Industry will discuss: General information on Biosecurity, tion of venereal disease at https://aaep.org/guidelines/infectious- Prebreeding / Breeding practices in farms, semen processing, disease-control/biosecurity-guidelines-control-venereally- shipment and handling, and signs of venereal diseases in horses. transmitted-diseases General practices in regards to horse movement onto a premise Biosecurity guidelines have been designed to be a management and the return home: Staff should be fully trained in the prevention tool for veterinarians and individuals involved in the equine breeding and recognition of various infectious diseases, including venereal industry. Biosecurity guidelines are however, only useful when they disease. Because the breeding industry involves the movement of are based on scientific evidence. Biosecurity guidelines are expected horses, semen, oocytes and embryos between farms, states, and to evolve and improve over time as new knowledge and tools countries there is ample opportunity to spread venereal pathogens. becomes available. Veterinarians, as part of their veterinarian-cli- Personnel should have standard procedures such as dedicated clean ent-patient relationship, should use evidence to reach their decisions clothing, hand wash and sanitizing protocols, and foot wear for an appropriate Breeding Farm Biosecurity program. There should washing, covers, instructions on no sharing of equipment when be a plan of action in an outbreak situation based on the unique ever possible, and disinfection protocols for shared equipment. circumstances such as the: risk, horse traffic, nature of the breeding Visitors should have access to only approved areas on the farm and operation, geographic location, horse density, horse demographics. their vehicles. Horse transporters should have designated areas for Having an effective means of assessing risk is a key component and parking loading and unloading. consideration of a biosecurity program. 20 www.theneaep.com 585-205-5122 THE CLINICIAN SUMMER 2018

The goal is to allow only healthy horses on the farm. Horses perceived risk, before being allowed to mingle with other horses on that are brought to breeding farms should have had a health check, the farm. Visiting horses should have their identification recorded such as a certificate of veterinary inspection, within the last 2 weeks. such as colour and markings, brands, tattoos, microchip numbers, Coggin’s test results for Equine Infectious Anemia is within the last or neckband number. Horses returning home should be examined 6 months is recommended. The horse owner should be required to for any signs of illness or injury. Horses also be isolated for 3 weeks disclose if there has been any infectious diseases on the home farm, after their return and observed for infectious disease. If visiting or that the horse was exposed to infectious disease within the last 2 horses are comingled it is better to group the horses by age, and to months. Horses with evidence of infectious disease, or fever should keep group sizes to less than 20 horses. not be allowed entry. Core vaccinations and risk based are recom- mended for all horses coming to a breeding operation. Pregnant PREBREEDING MANAGEMENT mares should be kept separate from all other horses on the farm especially after the 5th month. They should be kept in small (8 – OF MARES AND STALLIONS: Mares that are to be breed should have an examination 10) stable groups. While venereal diseases (EVA, EHVIII, CEM) are Mares: performed of the reproductive tract. Uterine cytology and culture may an obvious risk on breeding farms, other infectious diseases such as be required for barren or all mares before arrival for live cover. The strangles and equine herpesvirus 1 are also risks. The AAEP cytology is used to assist in the interpretation of the culture results. To guidelines on vaccination are found at https://membership.aaep.org/ obtain the samples the mares should have their tail wrapped. The iMISprod/AAEP/Sign_In.aspx?ReturnURL=/imisprod/securecon- person washing the perineum should wear gloves. Mild soap is used for tentsso/drupalsso.aspx cleansing the perineum prior to obtaining a uterine sample or for Horses should be placed in a holding area and have a pre-entry breeding. A clean hand dirty hand method should be used. The clitoral health inspection. To prevent the introduction of infectious diseases sinus and fossae should be cleansed. Twitches, hobbles, breeding rolls all new horses should be isolated for 1- 4 weeks depending on should be disinfected between mares.

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The Clinician 21 THE CLINICIAN SUMMER 2018

Stallions: Prebreeding management of stallions may include a covered garbage container. The teaser stallion should be monitored yearly determination of a stallion’s Equine arteritis virus (EAV) for his health status. Dismount samples may be evaluated for the status. Positive stallions should be tested for semen shedding of presence of white blood cells in sperm or from the mare’s uterus. EAV prior to the breeding season. A semen evaluation should be performed prior to the breeding season with a test cooling. Health certificates or proof of freedom from venereal diseases such as BREEDING SHED MANAGEMENT Taylorella equigenitalis may be required each breeding season. FOR ARTIFICIAL INSEMINATION: Horizontal transmission of disease is a risk with shared spaces BREEDING SHED MANAGEMENT and equipment. Holding areas for stallions prior to collection may become highly contaminated with venereal pathogens and act as FOR LIVE COVER: fomites. Stallions may scent mark the stall with urine and manure, Disease transmission in breeding sheds may occur through: they may masturbate in anticipation of collection. It is recommend- direct horse - to - horse contact, contaminated holding areas, ed that each stallion has his own breeding halter and lead, bucket, shared equipment, and people. The physical space should be easy to artificial vagina (AV) and cover. A protocol should be devised to disinfect. Holding stalls and holding areas are excellent places for prepare and then disinfect the holding stall and phantom. The back pathogen transmission. This should be routinely disinfected. Dirt and sides of the phantom where the stallion’s penis contacts the floors should not be used in holding stalls. Stallions should have surface should be covered with disposable plastic wrap prior to their penis washed by a person wearing gloves using warm water collection, which is discarded after each collection, the phantom and cotton and then dried before breeding each mare. The use of should be disinfected or a phantom cover should be used. After individual buckets or bucket liners is recommended. Personnel collection disinfectants, such as soap and water may be used on the assisting in directing the stallion’s penis into the mare, or collecting phantom, and 70% alcohol may also be used. a dismount sample should also wear disposable gloves. Gloves and Following semen collection the AV should be rinsed in very breeding roll covers should then be immediately discarded into a hot water to remove all debris, then treated with alcohol and rinsed with distilled water and treated again with 70% isopropyl alcohol and hung to dry in a non-dusty cabinet, out of direct sunlight. The cover of the AV should be wiped down with water and then wiped down with alcohol. The sink should be cleansed. We recommend for stallion’s that have regular semen collections that they each have their own AV and wash bucket. Semen Processing: Semen should be collected into a sterile bag. The semen should be filtered to remove debris and extended at least 1:1 with a semen extender containing sufficient quantities of an antimicrobial additive, such as antibiotics, to limit bacterial growth. Semen that is being shipped should be diluted a minimum of 1 part semen to 3 parts extender. Personnel should wear gloves. The working area, including counters and sinks, should be regularly disinfected. If a disease is suspected a sample should be obtained for culture or PCR prior to extending the semen. Following semen processing clean and disinfect the laboratory area and the stocks and flooring where the mare was bred. Personnel should wash hands when done. Semen is transported in a variety of containers that are meant to be disposable but are frequently recycled. These containers and their contents, such as ice packs should be disinfect- ed if reused. The containers that are designed to be reusable, such as Equitainers™ are easier to clean. We often advise owners to purchase a disposable container, or to purchase a shipment container that is sent back to them through surface mail for re-use.

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In situations where there is risk, such as during an outbreak, only form of the virus has an aerosol means of transmission. There is the new containers should be used. potential to cause disease outbreaks in immunologically naïve On Farm Handling of semen shipments: Semen shipments populations of horses such as at racetracks. Mares bred with EAV are a potential source of transmission of pathogens. The contents of positive semen could spread the infection to in contact pregnant the shipment should be considered as potentially infectious. All ma- mares. This is the reason they should be isolated after breeding. The terials used for AI should be properly disposed of. Shipping venereal strain however seldom causes abortion. Rarely EAV containers should be segregated. Dry shippers should be disinfected infection of pregnant mares has been associated with fatal viral after returning to the farm. Fresh nitrogen should only be used in pneumonia in newborn foals. dry shippers. Immunologically naïve mares bred with EAV infected semen Vaccines: A risk assessment for a farm is needed to devise a may experience a transient viremia and shed the virus, thus management strategy, as there are a variety of infectious diseases propagating the infection horizontally on a farm through the that affect horses and vaccination may be part of the management respiratory route, and through uterine secretions, or urine. The vast strategy. The AAEP guidelines on vaccination are found at: https:// majority of mares bred with infected semen are asymptomatic and membership.aaep.org/iMISprod/AAEP/Sign_In.aspx?ReturnURL=/ seroconvert. imisprod/securecontentsso/drupalsso.aspx EVA Pregnant Mares: Naïve pregnant mares infected with a virulent EAV strain will show typical flu-like signs, keratoconjuncti- VENEREAL PATHOGENS OF HORSES: vitis, limb edema, urticaria, or wheals. It has been reported that Equine Viral Arteritis: Equine Virus Arteritis (EVA) is caused some strains of EAV in immunologically naïve mares may result in by an arteriveridae, equine arteritis virus (EAV) which is an RNA abortion from 2 months to term, and occurs 3 – 13 days after acute virus. Seroprevalence to the EAV varies by bred: Standardbreds 70% exposure. Viral induced myoendometritis and vasculitis is present exposure, Thoroughbreds 2% - 10% exposure. Warmbloods are along with varying degrees of fetal autolysis. The equine arteritis also exposed. In most jurisdictions EAV is a reportable disease, and virus is isolated from fetal lungs and liver, and may be identified there have been outbreaks. This disease caused an outbreak in the with immunofluorescent staining for viral antigens. Clinical signs USA in 2006 that was spread by shipped semen [1]. are insufficient for diagnosis and paired serology or PCR of nasal The virus may be spread through direct contact with contami- swabs is needed for confirmation. Acute and convalescent serology nated equipment or by exposure to common holding stalls for with complement fixation will show evidence of infection. stallions, illustrating the importance of biosecurity measures. There EAV Sta llions: stallions are often infected near the time of is a more virulent respiratory form of EVA that causes a flu-like puberty. They are the natural reservoir of the virus. A proportion of illness with: mild upper respiratory disease, fever, depression, infected stallions become lifelong viral shedders. Virus is located in keratoconjunctivitis, limb and ventral edema, urticaria, or wheals. the accessory sex glands, especially in the ampullae. Shedding is The disease is manifested in horses largely as a subclinical dependent on testosterone. The stallions are usually carriers for life. disease, which is spread venereally. Equine viral arteritis is spread Recommend a pre-vaccination serology, followed by vaccination for venereally through semen from persistently infected stallions. The prevention. Negative serologic status or in positive stallions a venereal form of the disease was described in 1984, and subsequent negative virus isolation for EAV from semen, is required for export research identified non-sick chronically infected stallions, that to some countries. persistently shed EAV in their semen through their ampullary glands. The semen from these EAV shedding stallions readily infects EVA CONTROL MEASURES mares, even when present in small amounts in cryopreserved Natural infection: natural infection results in life long semen. Additives such as extenders with antibiotics and the routine immunity in the majority of mares, geldings, and stallions. Con- methods used to process semen for cryopreservation do not trolled exposure to EAV is sometimes used. eliminate the virus. Gradient separation and washing sperm to Modified Live Vaccine “Arvac” produced by Fort Dodge: remove the seminal plasma are needed to remove the virus. The An initial vaccination is followed by annual booster vaccinations. virus may also be spread through direct contact with contaminated Vaccinates or naïve mares bred to positive stallions should be equipment or by exposure to common holding stalls for stallions, isolated for at least 3 weeks, so any natural or vaccine strain virus illustrating the importance of biosecurity measures. Flu-like will not infect others. Sero-positive mares should be kept away from epidemics caused by EAV have also been reported. The flu-like others for 24 hours post mating. Pregnant mares in late gestation in

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a recent study had 3/19 vaccinates aborting, therefore in the face of from the Canadian Food Inspection Agency [3]. an outbreak vaccination is sometimes recommended [2]. Embryo CEM stallions and mares: The bacterial organism Taylorella transfer may also be a source of spread when embryos from donors equigenitalis colonizes the stallion’s penis, sheath, urethral fossa, bred with EAV positive semen are transferred to negative mares. urethra, and possibly accessory sex glands. Stallions do not show Colts are vaccinated at 6-9 months of age. Before vaccination of clinical signs. When infected stallions breed mares, the mares stallions or colts their seronegative status should be established. develop a mucopurulent cervicitis / endometritis that is usually self-limiting. Infection does cause transient infertility and thus CONTAGIOUS EQUINE METRITIS interferes with pregnancy in the cycle mares are infected. It may or Contagious Equine Metritis; Contagious Equine Metritis is may not require treatment, and on some occasions it may persist in caused by a Gram negative bacterial infection with Taylorella the uterus and the organism has been recovered from a placenta equigenitalis. The organism is usually spread by venereal means. The and fetus. It may be spread vertically from the dam to her offspring organism is present in horses in Europe, North America, South at birth or in utero. The organism colonizes the mare’s clitoral America, Asia and Africa. It has periodically resulted in outbreaks, region such as her clitoral sinuses and clitoral fossa. While this with a large outbreak in 2008 in the USA that involved trace backs to organism is at highest risk of spreading through live cover, the 2008 over 1100 horses in 48 states, and was estimated to cost $415 million outbreak was spread between stallions through fomites associated dollars. The CEM outbreak resulted in the detection of 28 infected with artificial insemination, such as the equipment, tease mares, horses in 8 states, and the USDA regulation of semen shipments from holding stalls, breeding phantoms, artificial vaginas etc. Artificial the USA to Canada through the process of Export Health Certificates, insemination using semen extenders with sufficient antibiotic and the Canadian mare owner’s requirement for an Import Permit concentrations have the capacity to decrease the spread of the disease. However, use for breeding of on farm collected semen and

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cooled semen that had antibiotics in the semen extenders still cleansed daily with 4% chlorhexidine and then packed with resulted in infections. This was an instructive lesson in how the nitrofurazone, or silversulfadiazine. Repeated negative cultures over biosecurity practices used were inadequate. Most disinfectants such different heats are needed to truly establish that a previously as chlorhexidine, ionic and nonionic detergents, and dilute bleach Taylorella equigenitalis infected mare has been cleared of the are effective in killing the organism [4,5]. infection. Clitorectomy is seldom used as there is doubt concerning Detection of Taylorella equigenitalis is through culture and the efficacy of the procedure. There is no vaccine available. Surveil- samples must be sent in Amies medium with charcoal to an lance of stallions and mares is the best means of detection and accredited laboratory and shipped overnight at 4°C. Suspect or control in advance of the breeding season. Negative cultures are newly imported stallions are bred to two mares to establish their required in some jurisdictions prior to breeding or for animal CEM status. The mare’s cervix is sampled on days 1, 3, 6, and 9 post movement. Suspect mares or stallions should be reported to the mating and if negative a complement fixation test is performed on USDA. Mares or stallions that have a previous history of Taylorella day 15. Additional measures include washing the stallion’s erect equigenitalis infection are considered high risk. Mares or stallions penis with 2% chlorhexidine solution for 5 days daily and then after that have been on a premises where CEM was detected are consid- each cleaning the penis is treated topically with nitrofurazine ered high risk [4,5]. ointment. A PCR test is available in some countries. There is a Equine herpesvirus-3 (EHV-3): Equine herpesvirus-3 is a similar organism called Taylorella asigenitalis that has been venereal disease sometimes called equine coital exanthema. This identified in donkeys and is non-pathogenic. It must be differenti- disease is not currently a reportable disease in the U.S. or Canada. ated from Taylorella equigenitalis through laboratory means [4,5]. Equine herpesvirus-3 is highly contagious and is typically spread by Taylorella equigenitalis infected mares are treated symptomati- coitus or by the use of infected semen for AI, however it may also be cally such as with uterine lavage and or systemic antibiotics. The passed between horses by nose-to-nose contact and by contaminat- perineal area and vaginal vestibule including the clitoral area is ed fomites. Disinfection of AV’s with alcohol is used to prevent

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spread of the virus. Stallions or mares with lesions should not be positive samples are confirmed using an AGID test (the “Coggin’s used for natural breeding. Stallions should be rested from semen test). These tests are used to detect carriers. There is no treatment collection until the lesions have fully resolved. The virus causes skin and no vaccination for the disease. This is a reportable disease and lesions that erupt in 5-10 days, which affects the perineum of the infected horses are usually euthanized. Therefore requiring a mare and results in lesions on the penis of stallions. The skin lesions negative test prior to entry at shows, sales, breeding farms is the best form blisters and then turn into scabs. When healed the herpes prevention strategy along with annual testing of all horses on a sores form raised whitish areas on the penis (not to be confused premises. A short EIA publication online with this information and with precancerous squamous cell carcinoma). Systemic signs of more on the disease may be found at http://publications.gov.sk.ca/ infection are rare. Reactivation of latency can occur under condi- documents/20/89130-Equine%20Infectious%20Anemia_June%20 tions of stress even years later, where new blisters form and may 2016.pdf result in a stallion refusing to serve an artificial vagina. This herpesvirus has not been associated with abortion. Diagnostic FOREIGN ANIMAL Testing is not usually performed as the lesions are very characteris- tic. If needed a diagnosis of EHV-3 may be confirmed by the VENEREAL DISEASES: Trypanosoma equiperdum, is a protozoal organism following methods: virus isolation, PCR from active lesions, Dourine: that causes dourine. This disease was formerly in the USA and was negative contrast electron microscopy of the lesions, and possibly spread predominately by infected carrier stallions breeding mares. by testing paired serum samples for a rise in neutralizing antibody The disease causes chronic fatal debilitation. It is still present in titers to EHV-3. For more information see https://aaep.org/ Africa and parts of the Middle East. The World Health Organiza- guidelines/infectious-disease-control/biosecurity-guidelines-con- tion ofr animals has additionation information found at trol-venereally-transmitted-diseases/equine-herpes-virus-3-ehv-3 http://www.oie.int/fileadmin/Home/eng/Animal_Health_in_the_ Biosecurity Guidelines: Dedicated artificial vaginas, barrier World/docs/pdf/Disease_cards/DOURINE.pdf procedures, disinfection protocols and gloves used in semen collection should be successful in preventing horizontal transmis- sion and contamination of breeding equipment in latent carriers or NON - VENEREAL INFECTIOUS stallions discovered to have lesions after collection. Stallions DISEASES THAT POSE A MAJOR needing tease mares for phantom collection of semen should be BIOSECURITY RISK ideally handled to avoid nose-to-nose or nose-to-vulva contact with Equine herpesvirus – 1: Equine herpesvirus-1 (EHV-1) is an theses mares. False mounting tease mares should be avoided. Tease alpha herpesvirus. Similar to other herpesviruses, EHV-1 infection mares should be visually inspected for EHV-3 lesions at each use. results in high proportion of horses developing life - long latent The virus is easily destroyed by common disinfectants such as infections, in addition there are reported breed differences in alcohol, heat, sunlight and drying. susceptibility. Latent EHV-1 carrier horses intermittently shed the This disease is also called Equine Infectious Anemia: virus. Latent virus may be detected in: CD8+ T cells, trigeminal “Swamp Fever” as the insect vectors favour wetland environments. ganglia, and submandibular lymph nodes of horses. Primary The virus causes high fevers, edema, lethargy, depression and EHV-1 infection or recrudescence of the infection is reported to sometimes death; and it may progress to a chronic debilitating form cause: respiratory disease, abortion, weak neonates and myeloen- where anemia is a prominent feature. Equine infectious anemia cephalopathy, which may occur as an outbreak. The genome of virus is a lenti virus that is spread by Tabanid flies such as horse flies EHV-1 is 152bp and a single nucleotide polymorphism (SNP) in and deer flies. These flies mechanically spread the virus through ORF 30, resulted in an amino acid substitution from asparagine their bites. It may also be spread by using common needles and (N752) to aspartic acid D752 in the DNA polymerase of the virus syringes or through fomites such as castration equipment or tooth [6]. The N752 strain is associated with clinical signs such as floats. Hence this disease poses a risk to all horses on a breeding respiratory disease and abortion, while the D752 strain is more farm. There is some information that a horse that is acutely commonly associated with neurologic disease. Animals such as clinically affected with equine infectious anemia virus may transmit donkeys (Equus asinus), onagers (Equus hemionus) and zebras the virus through blood associated with breeding and possibly (Equus burchellii, Equus grevyi) experience silent infections and may through semen. Antibodies to the equine infectious anemia virus serve as reservoir hosts. Cross species infections of the D752 strain in: are detected in serum samples using a c-ELISA test and then black bears (Ursa americanus), Thomson’s gazelles (Eudorcas

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thomsoni), guinea pigs (Cavia porcellus) have been fatal. Llamas in horses, and ability to infect other species, means most herds of (Lama glama), alpacas (Vicugna pacos), and blackbucks (Antelopa horses have previously exposed, latently infected members, such cervicapra) have also been infected. This is relevant in zoologic that a vaccine induced herd immunity, before natural infection, is collections where these animals should not be located near horses [7]. not achievable. A number of authors point to the need to induce Time of first infection: Colostral antibody levels against herd immunity through vaccination, based on the results of EHV-1 do not prevent EHV-1 infection in foals. Horses are infected experimental studies, which they recommend may be achieved by with EHV-1 early in life, presumably through contact with latently repeatedly priming the horse’s immune system with antigens. infected intermittently shedding equine carriers, which may include Because of the time frame for infection vaccination would have to their dams [8]. During competitions where large numbers of horses be started in neonatal foals, which is impractical. Challenge assemble, it is estimated that around 5% of show horses are actively experimental infections with a low amount of EHV-1 virus do not shedding virus [9]. Clinical signs of respiratory disease usually appear appear to mimic natural exposure levels. In challenge infections within 3 – 6 days of exposure. Horses are particularly at risk of vaccine induced antibody formation may assist in limiting viremia spreading the contagion if they are immunologically naïve or in the by binding to free virus, and vaccination under these circumstances early phase of EHV-1 infection, where viral shedding largely coin- has been shown to lower nasal shedding of virus [10]. The immune cides with the high fever. Current experimental infection models system responds to the frequency, amount and the character of the likely do not mimic the natural ecology of the virus where the virus is antigen exposure. Frequent vaccination using killed vaccines against shed from multiple horses for multiple days. It has been reported that EHV-1 may bias the immune response towards an antibody rather previously EHV-1 exposed horses in challenge studies, using low than a cell mediated immune response, which is associated with doses of virus experience less clinical disease and shed less virus in a protection [11]. Vaccination against EHV-1 has been suggested to subsequent low doses viral challenge infection [10]. be related to increased susceptibility to neurotropic EHV-1 [11]. Herd Immunity: The endemic presence of EHV-1 infection Studies on the performance of killed and modified live virus

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vaccines against EHV-1 are far from convincing in terms of vaccine should have a communication, isolation and quarantine contingen- efficacy in protecting against abortion [12-14]. There is no report cy plan in the event of an EHV-1 outbreak. of a natural outbreak where vaccinated horses appeared to be Prevention: Appropriate biosecurity provisions in breeding protected from either abortion or herpes myelitis. Horses may be facilities should be used. Prevention of EHV-1 induced abortion infected by more than one herpesvirus strain, such as D752 and includes having mares in small groups that are sorted by age and N752 and there appears to be no cross protection between strains. pregnancy status, and prevention of new introductions into the In abortion outbreaks mares that do not abort may deliver foals mare groups after the 5th month of pregnancy. Mares, or mares and that are infected, weak and perish or that survive and shed virus in foals arriving at breeding facilities should have their temperature the first few days of life [15]. pulse and respiration taken, and mares with fevers or signs of EHV-1 infection results in mild respiratory infection and neurologic disease or mares whose foals have fevers should not be abortion from 1 week to several months after infection. Thus rising off loaded or brought to the breeding shed. Horses returning from titers to EHV-1 are not always present. The strong social ordering of show or competitions should be kept separate from other horses. horses means that large groups (<20 horses) or new introductions The benefit of vaccination of horses against EHV-1 in experi- that cause a reordering are stressful for horses and may result in mental low dose challenges has been established, but under field viral recrudescence [16]. Older mares usually rank high in the social conditions the vaccine may not be effective, and no vaccination will order and management practices that group mares by age are be able to compensate for poor management practices. Clinical advisable [17]. In the 5th month of pregnancy mares become cases of EHV-1 and EHM should be isolated, treated symptomati- susceptible to abortion caused by EHV-1. The majority of the cally and the farm voluntarily quarantined for at least 14 days after abortions associated with EHV-1 are in late pregnancy. The prompt the last detection of viral shedding. Further research in EHM is isolation of aborting mares, removal of the products of abortion, clearly needed. and disinfection of the area is helpful in preventing or limiting Summary: Horses are infected with EHV-1 as foals and the transmission. Under ideal conditions EHV-1 may survive for up to majority become chronic latent carriers of the virus. Equine herpes- 35 days in the environment. virus-1 vaccines do not reliably prevent: infection, development of EHM: Equine herpes myelitis (EHM), usually appears within viremia, cross protection against other strains, nor do they prevent 2 weeks of respiratory disease and is recognized by “dog sitting” the establishment of latency. There is no vaccine with a label claim where the horse is able to rise up on the front end but the hinds against the neurotropic strain of EHV-1. Outbreaks of EHV-1 limbs are paralyzed, and recumbency, decrease anal tone, and related disease continue in vaccinated horses. More information is bladder paralysis may be present [18]. Lameness and hind end available at https://aaep.org/guidelines/infectious-disease-control/ weakness have also been reported. The odds of developing neuro- equine-herpesvirus-resources The EHV-1 Consensus statement is logic disease following EHV-1 infection was 162 times more likely available at http://onlinelibrary.wiley.com/ with the neurotropic strain than with the non-neurotropic strain doi/10.1111/j.1939-1676.2009.0304.x/pdf [20]. [18]. The optimal treatment and risk reduction therapy are still a Other noteworthy biosecurity risks include Strangles: work in progress, and currently non-exposed horses should be Strangles is an infectious Gram positive bacterial disease caused by considered for vaccination with a modified live EHV-1 vaccine if Streptococcus equi. It may be introduced through carrier animals they are on the premises or must enter the premises and have not who shed the organism into the environment. This disease is been vaccinated in the previous 90 days, but exposed horses should generally found to cause acute fever followed by mucopurulent not receive a booster with a modified live EHV-1 vaccine. The case nasal discharge that may progress to lymph node enlargement and fatality rate and loss of function of many horses infected with the abscess formation. Affected and exposed horses should be isolated. neurotropic strain of the virus is significant, and any horse exhibit- There is a MLV Strep equi vaccines available that may be used in ing signs of EHM should be immediately quarantined. No farms with endemic problems. Sweeney et al. 2005 authored a equipment or personnel movement between the quarantined area position statement on Strangles [21]. with affected horses and the other portions of the property should occur. If testing is not available for EHV-1 from nasal swabs or References: blood the affected horses should be monitored and kept separate 1. Timoney P, Creekmore L, Meade B, et al. 2006 Multi-state for 21days after clinical signs have stopped [18, 19]. Each farm occurrence of EVA, in Proceedings. 110th Annual meeting of the United States Animal Health Association 2007, p.354–362.

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2. Erdman M, Creekmore L, Fox P, et al. Diagnostic and 16. Curry MR, Eady PE, Mills DS. Reflections on mare epidemiologic analysis of the 2008 - 2010 investigation of a multi-year behaviour: social and sexual perspectives. J of Veterinary Behavior: outbreak of contagious equine metritis in the United States. Prev Vet Clinical Applications and Research. 2007. 2(5):149-157. Med 2011;101:219–28. 17. Heitor F, do Mar Oom M, Vincente L. Social relationships in 3. Luddy S, Kutzler M. Contagious Equine Metritis Within the a herd of Sorraia horses: part I. Correlates of social dominance and United States: A Review of the 2008 Outbreak. J Eq Vet Sci 2010: contexts of aggression. Behavioral Processes. 2006. 73(2): 170-177. 30(8): 393-400. 18. Kohn CW, Fenner WR. Equine herpes myeloencephalopathy. 4. CEM OIE manual https://web.oie.int/eng/normes/MMANU- Vet Clinics of North America. Equine Practice. 1987. 3(2):405-419. AL/2008/pdf/2.05.02_CEM.pdf 19. Perkins GA et al., Investigation of the prevalence of a 5. CEM Fact sheet Iowa State http://www.cfsph.iastate.edu/ neurologic equine herpes virus type 1 (EHV-1) in a 23-year retrospec- Factsheets/pdfs/contagious_equine_metritis.pdf tive analysis (1984-2007). Veterinary Microbiology. 2009. 6. Allen, GP. Epidemic disease caused by equine herpesvirus-1: 139(3/4):375-378. recommendations for prevention and control. Equine Veterinary 20. Lunn DP, Davis-Poynter N, Flaminio MJBF, et al. Equine Education. 2002.14(3):136-142. Herpesvirus-1 Consensus Statement. 2009. J Vet Internal Med 2009. 7. Wohlstein P, Lembecker A, Spitzbarth I, et al. Fatal epizootic 23:450-461.http://onlinelibrary.wiley.com/ equine herpesvirus I infections in new and unnatural host. Vet doi/10.1111/j.1939-1676.2009.0304.x/pdf Microbiol 2011. 3/4: 456-460. 21. Sweeney C, Timoney JF, Newton JR, et al., Streptococcus 8. Gilkerson JR, Whalley JM, Drummer HE et al. Epidemiologi- equi infections in horses; Guidelines for treatment Control and cal studies of equine herpes virus-1 (EHV-1) in thoroughbred foals. A Prevention of Strangles. J Vet Internal Med 2005. 19:123-134. review of studies conducted in the Hunter Valley of New South Wales between 1995 and 1997. Vet Microbiol. 1999. 68:16-25. 9. Perkins GA, Goodman LB, Dubovi EJ, et al. Detection of equine herpesvirus-1 in nasal swabs of horses by quantitative real time PCR. Improving the life of your Journal of Veterinary Internao Medicine. 2008. 22(5):1234-1238. horse is a JOINT EFFORT. 10. Kydd JH, Townsend HGG, Hannant D. The equine immune response to equine herpesvirus-1: the virus and its vaccines. Veterinary Immunology an Immunopathology 2006. 111(1/2): 15-20. 11. Paillot R, Case R, Ross J, et al. Equine Herpes virus-1: virus, immunity, and vaccines. The Open Veterinary Science Journal. 2008. 2:68-91. 12. Henninger RW, Reed SM, Saville WJ, et al Outbreak of neurologic disease caused by equine herpesvirus-1 at a University Equestrian Centre. Journal of Veterinary Internal Medicine. 2007. 21(1):157-165. 13. Burgess BS, Tokateloff N, Manning S, et al. Nasal Shedding helps maintain joint mobility and flexibility of equine herpesvirus-1from horses in an outbreak of equine herpes for horses. EQUISTRO® has been a trusted myeloencephalopathy in Western Canada. J of Vet Internal Medicine. brand of equine products available throughout Europe for 2012. 26:384-392. over 30 years and used by the top riders in the world. Once- daily administration promotes cartilage development and joint 14. Bürki F, Rossmanith N, Nowotny N, et al Viraemia and health at the immunologic level. abortions are not prevented by two commercial equine herpesvirus-1 Enhance the body’s normal repair of cartilage and joints vaccines after experimental challenge of horses. Veterinary Quarterly. Help maintain joint mobility and flexibility 1990. 23 (2): 80 -86. Help support the structural integrity of joints 15. Gardiner DW, Lunn DP, Goehhring LS, et al., Strain impact Support a healthy inflammatory response on equine herpesvirus type 1 (EHV-1) abortions models: Viral loads in Contact your distributor today to purchase. fetal and placental tissues and foals. Vaccine. 2012. 30:6564-6572. 1.800.267.5707 www.vetoquinolusa.com

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Neonatal Problems in the Draft Horse Melissa Restifo, DVM, DACVIM (LA) Brandon Equine Medical Center

ABNORMALITIES OF DRAFT MARE already predisposes mares to dystocia, and mares with dystocia Prior to covering the problems known to affect draft foals, it is already have an increased rate of incidence of retained placenta relevant to briefly consider some of the many pregnancy related (65% and 79% in different studies). No specific genetic, metabolic, problems that are reported to occur more commonly in draft or fetus-related etiology elucidated in any breed, except the Friesian, mares. These including poor fertility, pre-pubic tendon rupture, where at least one publication has suggested inbreeding as a twinning, dystocia, and retained placenta. contributing factor to retained placenta. One study did examine the Of these, the most potentially catastrophic is frequency of placentas of draft mares, and histologically compare those that were twinning in draft mare, with up to 25% double ovulating and retained with those that passed normally. This revealed that providing the potential for a twin pregnancy. In addition, given the retained fetal membranes were associated with adhesion of the large uterus of the draft mare, they are more likely to carry twins to allantochorion to the endometrium in 88% of the mares, and that late into gestation, with many cases only being recognized at the this adhesion depended upon a number of factors. These included time of foaling. Delivery is often complicated in this situation, with fibrosis of the lamina propria of the allantochorial villi and the dystocia all but guaranteed. Draft mares are already considered high allantochorial stromal connective tissue, overdevelopment of the risk for this complication due to size and an apparent increase in allantochorial stromal connective tissue, oversized allantochorial the proportion of malpositioned foals. Twinning also has signifi- epithelial cells, and sparser and less-branched allantochorial villi. cant implications for the foals, should they survive, as they are often Uterine atony and over-rapid involution of the uterus were also born premature and are at high risk of failure of passive transfer, recognized as rarer causes of retention of the fetal membranes in orthopedic dysfunction, and neonatal maladjustment syndrome, this population. Also of interest is that draft mares are anecdotally among several other problems. It is critical to assess mares at 14-16 at higher risk of laminitis related to retained placenta, which has days of gestation in order to best assess for the presence of twins, been historically attributed to their weight placing more strain on and reduce one if the pregnancies are adequately separated. A the bony column when the laminae are weakened. One publication detailed discussion of twin reduction is beyond the scope of this was able to show an increase in the incidence of metritis-related discussion, however relevant information about the management post-partum fever in draft mares compared to light breeds, with a of critically ill foals (such as a twin) will be covered in the discus- relatively high incidence of laminitis within that population. sion of neonatal maladjustment syndrome. Luckily, should both Idiopathic Hyperthermia (IH) survive, the draft mare is known for her overzealous milk produc- IH is a poorly documented syndrome thought to preferentially tion and excellent maternal instincts, and is often capable of affect draft breed foals, and is characterized by an elevated body supporting both foals to weaning, given her nutritional status is temperature (>102̊ F; often up to 104̊-105̊) with no apparent well managed. cause. Affected foals are often also tachypneic, but otherwise bright While a retained placenta does not have a direct impact on the and apparently normal with good nursing behavior. Treatment of foal, certainly the health of the mare does. It has been well estab- this condition is typically symptomatic, including evaporative lished that draft mares are predisposed to retained placenta, with as cooling of the foal via ice/alcohol baths and the use of fans, many as 54% of mares affected. This is not surprising when you administration of chilled intravenous fluids, and body clipping if consider that the size of draft foals and frequency of malpositioning the coat is heavy. Most foals recover without incident in 1-2 weeks,

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but must be monitored closely and kept out of the heat and optimal perfusion, which leaves other organs such as the GIT, humidity in the interim. This is not to be confused with hyperther- kidneys, heart, and lungs, more susceptible to insult. In addition, mia associated with macrolide administration, often recognized these foals are often recumbent with compromised immune during treatment of Rhodococcus equi, which we now know is systems, and so secondary infections and complications related to related to the induction of anhidrosis in treated foals. nursing care are common. Possible complications include pneumo- nia, umbilical problems (patent urachus, oomphalitis), renal NEONATAL MALADJUSTMENT dysfunction, ileus, septic joints, pressure sores, uroperitoneum, and MODS. Drafts in particular seems pre-disposed to pressure sores SYNDROME (NMS) and uroperitoneum, both of which are related to their large size, NMS occurs in approximately 3-5% of live births, and is and the latter of which is likely related to the foals’ lack of enthusi- considered one of the most common diseases affecting neonatal asm when being assisted to rise. foals in the first several days of life. Draft foals in particular appear Much recent research on NMS has focused on whether oxygen to be more susceptible to this condition, with many large breeders deprivation really plays a dominant role in the condition in all foals. anecdotally reporting more than one case in a breeding season, for While histopathology in some foals is consistent with cerebral multiple seasons in a row. In addition to NMS, the disease has been hemorrhage, edema, and hypoxia and/or ischemia, others do not referred to as neonatal encephalopathy, hypoxic-ischemic encepha- exhibit any of these changes, and a subset of affected foals even have lopathy, perinatal asphyxia syndrome, and dummy foal syndrome. Affected foals are largely normal for hours to days (<72 hours) after birth, at which time a variable number of clinical signs, largely defined by central nervous system (CNS) dysfunction, may develop. Owners of mildly affected foals may describe a poorly defined change in nursing behavior or demeanor, aimless wandering, “losing” the udder, and licking inanimate objects, while more severely affected foals may exhibit alterations in consciousness, head pressing, auditory or dermal hypersensitivity, weakness or incoordination, or even generalized seizures. The disease has been historically linked to cerebral hypoxia or ischemia in the perinatal period, which causes neuronal cell energy depletion and death. Risk factors for such an event are recognized in several periods: pre-partum (related to the mare), or peri- or post-natally related to parturition or the foal itself. Risk factors related to the mare includes anything that causes decreased blood flow or oxygen delivery to the uterus, such as anemia, cardiovascu- lar or respiratory disease, general anesthesia, placental abruption or dysfunction, placentitis, and SIRS. Parturition related factors include dystocia, red bag delivery, prematurity, cesarean section, and uterine intertia. Risk factors in neonates are related to any cause of illness or compromise, such as neonatal isoerythrolysis, umbilical hemorrhage or infection, generalized sepsis, cardiovascu- lar or respiratory disease, hypothermia or starvation, or concurrent CNS disease/infection (among others). Why draft foals are particu- larly predisposed has not been specifically investigated, however their large size and the propensity for peri-partum complications in draft mares (dystocia, placentitis) is certainly suggestive. The sequelae to NMS can vary from mild to severe, depending on the severity of the disease. Many result from redirection of blood away from the "less vital" organs in order to provide the brain with

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a normal birth, with a relatively quick and complete recovery from of the disease, all that may be needed is assistance and encourage- the condition. And so, in addition to ischemic disease, we must also ment to nurse, sometimes with colostrum administered enterally. consider postnatal persistence of, or reversion to, an inhibited fetal However severe cases may require frequent tube feeding, nursing state of cortical function (consciousness) as a contributing factor. It care, fluid resuscitation, respiratory support (oxygen, stimulants, this group of neonates that has been the focus of research out of mechanical ventilation), and seizure control. Of course, depending UC Davis which suggests that abnormal levels of neurosteroids on concurrent conditions, other supportive care such as anti-in- – naturally occurring chemicals that keep the foal quiet in the flammatories, corticosteroids, antimicrobials, and vasopressors may womb – may be a potential cause of NMS. These neurosteroids can be indicated as well. cross the blood–brain barrier and have neuromodulatory effects, Recent data on the outcome of foals with NMS revealed that and it is suspected that a subset of foals with signs of NMS may not 79.8% survival to hospital discharge, but that hospital stays were actually be the result of hypoxia, but rather an increased level of long (averaging 7-10 days), and that survival was associated with these neurosteroids. several clinical and hematologic parameters, as well as therapeutics. It is thought that the stress experienced by the foal during These included the use of pressors, recumbency, co-morbidities, normal parturition, which includes the pressure of passing through and some blood parameters (high calcium and low ALP). Interest- the pelvic canal, signals a decrease in these neurosteroids. When this ingly, non-survival was not associated with maternal factors such as stress is not present or not effective, as with cesarean sections or dystocia, caesarian section, and placentitis, although these were when a foal travels abnormally through the birth canal, these associated with the likelihood of disease. It is important to consider neurosteroids remain activated, keeping the foal in a quiescent that this data was obtained over a number of years from a referral “dummy” state. One study found sedative neurosteroids persist and institution, and may not be directly applicable to an ambulatory are often elevated in the bloodstream of dummy foals, and another population. The take home from this group was that supportive found that a healthy foal infused with allopregnanolone (a neuros- nursing care is the therapy most essential to a positive outcome. teroid metabolite) exhibited obtundation, lack of affinity for the mare, and decreased response to external stimuli. Refereneces: Part of the solution for this subset of foals, is to mimic the Aleman M, Pickles KJ, Conley AJ, et al. Abnormal plasma pressure experienced during normal parturition using a simple neuroactive progestagen derivatives in ill, neonatal foals presented to rope harness (the “Madigan Squeeze”). This procedure uses the neonatal intensive care unit. Equine Vet J 2013 Nov;45(6):661-5. assertive tactile stimulation to elicit locus coeruleus-noradrenaline Aoki T, Kimura Y, Oya A, et al. Hematologial and biochemical mediated neuroactivation, which is normally stimulated during features of postpartum fever in the heavy draft mare. J Equine Sci parturition. In this procedure, pressure is applied with a rope 2016;27(1):13-16. around the thorax, causing the foal to lie down and appear to fall Diesch TJ, Mellor DJ. Birth transitions: pathophysiology, the asleep. Approximately 20 minutes later, the rope pressure is released onset of consciousness and possible implications for neonatal malad- and in some cases improvements have been immediate and justment syndrome in the foal. EVJ 2013;45:656-660. dramatic, with foals standing and nursing within minutes. Another Frazer GS, Perkins NR, Blanchard TL et al: Prevalence of fetal therapeutic which has not yet been investigated in NMS but could maldispositions in equine referral hospital dystocias. Equine Vet J be a focus of future research, is the use of neuroactivators such as 1997;29:111-116. estradiol 17β in affected foals. Only once study has been performed Hurcombe, SDA: Emergency Problems Unique to Draft Horses. in animals, however it showed that the drug promoted behavioral In: Orsini JA and Divers TJ (ed): Equine Emergencies: Treatment arousal and breathing in lambs delivered via hysterectomy which and Procedures (ed 4). St. Louis: Elsevier Saunders, 2014;652-655. had been inactive and “flat” post-delivery. Ishii M, Shimamura T, Utsumi A, et al. Reproductive perfor- Prevention of NMS is not possible, however many breeders mance and factors that decrease pregnancy rate in heavy draft horses will prophylactically hyper-oxygenate foals in the first 10-15 bred at the foal heat. J Equine Vet Sci 2001 Mar 31;21(3):131-6. minutes post-partum, and feel it does have an impact for those Ishii M, Aoki T, Yamakawa K, et al. Relationship between the without risk factors for ischemia or hypoxia (i.e. those with a placental retention time and the reproductive performance at the foal normal birth), causing them to stand and nurse more rapidly than heat in the thoroughbred mare and a comparison with heavy draft. J foals not treated with oxygen. Otherwise, management of NMS Equine Sci 2013;24(2):25-29. foals is largely supportive in nature, and often involves round the Kimura Y, Aoki T, Chiba A, et al. Effects of dystocia on blood gas clock intensive care. Depending on the individual and the severity parameters, acid-base balance and serum lactate concentration in

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heavy draft newborn foals. J Equine Sci 2017;28(1):27-30. Sabbagh M, Danvy S, Ricard A. Genetic and environmental Lyle-Dugas J, Giguère S, Mallicote MF, et al. Factors associated analysis of dystocia and stillbirths in draft horses. Animal 2014 with outcome in 94 hospitalized foals diagnosed with neonatal Feb;8(2):184-91. encephalopathy. Equine Vet J 2017 Mar;49(2):207-210. Sevinga, M, Barkema HW, Stryhn H, et al. Retained placenta in Madigan JE, Haggettt EF, Pickles KJ, et al. Allopregnanolone Friesian mares: incidence, and potential risk factors with special infusion induced neurobehavioral alterations in a neonatal foal: is this emphasis on gestational length. Theriogenology 2004;61(5): 851-859. a clue to the pathogenesis of neonatal maladjustment syndrome? Sevinga M, Vrijenhoek T, Hesselink JW, et al. Effect of inbreed- Equine Vet J Suppl 2012 Feb;41:109-12. ing on the incidence of retained placenta in Friesian horses. J Animal Miller A, Woods GL. Diagnosis and correction of twin Sci 2004 Apr 1;82(4):982-6. pregnancy in the mare. Vet Clin North Am Equine Pract 1988 Toth B, Aleman M, Brosnan RJ, et al. Evaluation of squeeze-in- Aug;4(2):215-20. duced somnolence in neonatal foals. Am J Vet Res 2012 Rapacz A, Paździor K, Raś A, et al. Retained fetal membranes in Dec;73(12):1881-9. heavy draft mares associated with histological abnormalities. J Equine Vet Sci 2012 Jan 31;32(1):38-44.

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Making Rehabilitation “REAL” for your practice: Rehab Basics Katie Seabaugh, DVM, MS, DACVS, DACVSMR College of Veterinary Medicine and Biological Sciences Colorado State University

INTRODUCTION maintained on strict stall rest. Research has shown that immobili- The interest in equine rehabilitation has grown in recent years. zation results in decreased bone mineral density, degeneration and Much has been focused on musculoskeletal rehabilitation and that resorption of articular cartilage, muscle atrophy, synovial mem- is largely what will be discussed here but rehabilitation for neuro- brane atrophy, increased stiffness in peri-articular tissues and logic disease, wounds, and even abdominal surgery should not be decreased maximum load to failure in ligaments.(1) More severe overlooked. The importance of rehabilitation following injury has changes occur with strict immobilization (i.e. cast placement) but been known in the human realm for many years. Canine rehabili- similar changes should still be expected with strict stall rest. tation has also gained in popularity and in many ways is more Free choice turnout is another recommendation that should be advanced than what we know in equine rehabilitation. avoided. Horses are not known for taking good care of themselves. That may be what got them to visit you in the first place. Turnout does keep the horse active but we cannot control their activity level. THE BASICS Repeatedly, horses that have been turned out for a period of time are The basics of equine rehabilitation are based on decades of still lame when they are re-evaluated. Now it is 6 months later and equine musculoskeletal injuries. That being said, it wasn’t always we are still at square one or even worse, we have a more severe injury referred to as equine rehabilitation. This information was obtained than we did originally. There are select injuries that do better with from years of experience of getting horses back to work after injury. increased turnout but those are the exceptions rather than the rule. So why the interest and focus on rehabilitation now? With ad- vancements in imaging and therapeutics, including biologic therapies, a greater expense is being put forth to diagnose and treat WHAT TO INCLUDE injuries. Now that we can accurately diagnose and treat an injury Things that should always be included in a basic rehabilitation how can we support those modalities and get the horse back to plan are scheduled rechecks, which may or may not include work? Lets start out by keeping it simple: what to avoid and what imaging, detailed expectations, explicit instructions. If owner’s are to include. aware from the beginning that imaging will be repeated they are more likely to be willing to pay for it. Also, if they know they will have to return for re-evaluation they are being held partially WHAT TO AVOID accountable for the rehabilitation protocol. Detailed expectations There are two things that should be avoided when creating an may keep your owner’s anxiety reduced. If the owner understands equine musculoskeletal rehabilitation program: strict stall rest and that they horse may still be lame at the 2 week recheck then it isn’t a free choice pasture turnout although there are exceptions for each. surprise when the horse is still lame. Also, if they owner knows that Strict stall rest still has a place in regards to equine injuries. the horse will not return to work for 6 months, they won’t be Obviously, a horse that has a third metacarpal fracture repair is disappointed when the horse is still tack walking at 3 months. going to be placed on stall rest. That being said, there are some Lastly, providing explicit instructions allows owners to stay focused. rehabilitation modalities that can still be used even when a horse is It is better to error on too specific then to leave details out that may stall bound. Aside from fracture repair, horses should not be have been followed.

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BASIC REHABILITATION EXERCISES Surgical site massage Deep massage of the surgical site should be performed daily Making the owner an active participant after sutures have been removed. This may help to decrease It is important that, as veterinarians, we establish our role in adhesion formation at the incision site. the diagnosis of lameness. Our education and experience is valuable. Getting the owner, however, involved in a rehabilitation Obstacles plan is also important. The veterinarian should make the specifics When tack walking is re-introduced into a rehabilitation of the rehabilitation plan but additional strengthening exercises can program, you can also incorporate low strain obstacles to keep the be added to the plan to allow the owner to choose other strengthen- owner and horse focused. Ground poles provide the horses ing exercises. Frequently, horses went from a minimum of 45 something to focus upon and also increase active range of motion. minutes of exercise a day to stall rest and 5-10 minutes of hand- Patterns can improve balance and proprioception. As the rehab walking. There can be a variety of additional exercises that you can program progresses you can increase to raised cavalettis. recommend to the owner to fill that additional 35-40 minutes that they would have spent riding their horse. CONCLUSION There are other more injury specific exercises that can be Range of motion exercises included, such as lateral tail pulls, pelvic tilt, back flexion and When a horse is placed on a controlled exercise program extensions and more. These will be discussed in more detail in the following injury we significantly reduce their activity level. With lecture. Overall there is a wide range of basic rehabilitation this exercise reduction we may also reduce range of motion. Simple exercises that can be offer to horses and their owners. Creating the range of motion exercises can be recommended to the owner to try right plan for each horse can take time and patience but the end to minimize stiffness in peri-articular tissues. result is worth it. Pull at the toe for maximum flexion Push at the toe for maximum extension References 1. Paulekas R, Haussler KK. Principles and Practice of Stretching Therapeutic Exercise for Horses. J Equine Vet Sci. 2009;29(12):870-93. Prior to each ride stretch the upper body muscles of each front leg. This is achieved by pulling the leg forward and holding it for 5 seconds and then pulling the foot backward and holding for 5 seconds. Repeat 5 times for each leg. “Carrot stretches” are another stretching exercise that can be done to strengthen the muscles of the horse’s core while they are rehabilitating an injury. This will help stabilize the back and abdomen. It may appear that the horse is only moving his neck but you will see that they are flexing and extending their back as well. The following exercises should be performed ~ 3 times a week. Each stretch should be performed for 5 repetitions. The goal is to get the horse to hold the stretch for 5 seconds initially and slowing increasing the duration that the horse has to hold the stretch. 1. Extension a. Nose is up and forward as high as the horse can go 2. Flexion a. Chin to chest b. Chin to carpi c. Chin to fetlocks 3. Lateral Flexion (to each side) a. Chin to girth b. Chin to stifle c. Chin to hock or hind fetlock (* only if well tolerated) The Clinician 35 THE CLINICIAN SUMMER 2018 NEAEP

Imaging of the Equine Axial Skeleton Sarah M. Puchalski, DVM, DACVR Circle Oak Equine Sports Medicine

• Complex anatomy and size of the horse make of Increasing exposure time can mitigate the problems of underexpo- the axial skeleton imaging challenging sure but results in greater motion artifact. Furthermore, images • Variable clinical manifestations made on small detectors intended for extremity work can be • Consider the limitations of each imaging technique confusing to interpret as the images often display few vertebrae or at the outset intervertebral articulations. Thus DR images must be subjected to critical assessment of quality prior to their use as a diagnostic tool. Diagnostic imaging of the axial skeleton in the horse remains a High quality radiographs of the cervical vertebrae provide a challenge for equine practitioners. Vast improvements in our wealth of information about vertebral morphology.1,2 However, collective understanding of the anatomy, pathology, and clinical latero-lateral radiographs have several limitations including: manifestations of disease, along with tremendous advances in superimposition of the bone over the soft tissues of the spinal cord diagnostic imaging technology have overcome some of the difficul- and articular process joints, a lack of orthogonal projections, and ties posed by the large size and complex anatomy. that they are generally taken with a fixed or stationary head An improved understanding of the complex intersection of the position. These limitations can be partially alleviated through nervous and musculoskeletal systems has provided background quantification of the sagittal diameter ratios, the use of oblique and information to understand numerous, relatively novel clinical /or positional projections and complementary imaging techniques manifestations of axial skeleton dysfunction. Pain and stiffness of such as ultrasound, and the use of contrast media (myelography). the axial skeleton, typically leading to decreased performance, are Thoughtful consideration of the limitations and their respective clinical signs that are well accepted. Abnormal head carriage, solutions should enter into the clinicians’ rationale early in the inflexibility, unilateral forelimb lameness, bilateral forelimb discourse. When quantification of sagittal diameter ratios and lameness, fixed (locked) head or neck position, neurological myelography are employed, it is important to remember that even dysfunction, abnormal unilateral or bilateral hind limb gait, poor these techniques are faulted. Inter- and intra-observer variability in lumbosacral extension, among other clinical complaints are better ratio measurement make the use of this technique somewhat understood with greater knowledge and useful ante-mortem questionable except in very positive or very negative cases.3 diagnostic imaging techniques. Similarly, myelography, though for a time considered to be gold Digital radiography (DR) has improved the utility of routine standard for the identification of spinal cord compression, is radiographs in the standing horse. While the lumbar spine still fraught with false negative and false positive results. Even with these proves challenging due to the anatomic shape of the region and limitations, radiographs are still useful for the evaluation of the overlying soft tissues, high quality radiographs of the cervical and shape, size, alignment, symmetry, opacity, and number of vertebrae most of the thoracic spine can be acquired in most adult horses. giving good information about many disease processes. Caution is urged for some anatomic regions when utilizing portable Ultrasound is invaluable for the assessment of the vertebral radiography equipment. Most portable x-ray generators intended surfaces and associated soft tissues, and for its role in ultrasound for extremity use lack the tube output needed for proximal guided or ultrasound assisted interventions. In general, ultrasound appendicular and axial skeleton radiographs. Underexposure does not provide useful information for the assessment of the manifests as image noise in DR and detracts from image quality. central nervous system. Evaluation of the nerve roots can be

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performed in the lumbosacral region on per-rectal ultrasound vertebral morphology but more limited information about the examination providing some information about these structures. spinal cord and nerve roots. CT myelography allows for indirect Ultrasound is complementary to radiographs for evaluation of the assessment of central nervous system in a cross sectional manner. nuchal ligament and bursa, articular processes and joints of the Lesions of the central nervous system and vertebrae identified on cervical, thoracic and thoracolumbar spine, the supraspinous CT and CT myelography include extra-dural spinal cord compres- ligament, the interspinous ligaments and spacing of the thoracic sion, intra-dural, extramedullary lesions, intervertebral foramenal and lumbar dorsal processes. In the thoracic and thoracolumbar stenosis due to articular process joint enlargement or periarticular spine, ultrasound of the dorsal aspect of the spinous processes and new bone proliferation, intervertebral disc pathology, osseous supraspinous ligament can be very misleading for the diagnosis of pathology of the vertebral bodies or processes, and skeletal trauma spinous process impingement and should always be used in concert among other conditions. This allows for the evaluation of many with radiographs. Ultrasound alone can be used for evaluation of conventional and non-conventional clinical manifestations of axial the pelvis and sacroiliac region including the associated soft tissues, skeleton dysfunction. but is often more useful when in conjunction with nuclear scintig- Diagnostic imaging of the axial skeleton should be considered raphy. Ultrasound is often used to guide intra- or peri-articular for a broad range of disorders. All imaging techniques can be used injections of the intervertebral joints or sacro-iliac regions, or to clinically and as research tools to further the collective understand- sample CSF from various locations. ing of this loose assortment of highly varied conditions. Advances Nuclear scintigraphy is a mainstay diagnostic technique for in this field should be forthcoming as imaging techniques such as many disorders of the axial skeleton. This technology provides CT and robotics become more available to practitioners. important information for difficult anatomic regions, particularly when used in concert with radiography or ultrasound. Scintigra- Recent Related Publications: phy aids in the determination of lesion activity through mapping 1. DeRouen A, Spriet M, Aleman M: Prevalence of Anatomical areas of osseous turnover and should be considered critically Variation of the Sixth Cervical Vertebra and Association with important in the assessment of skeletal trauma including stress Vertebral Canal Stenosis and Articular Process Osteoarthritis in the fractures, articular process osteoarthritis, dorsal spinous process Horse. Vet Radiol Ultrasound 57:253-258, 2016. impingement, and most disorders of the pelvis. The accumulation 2. Santinelli I, Beccati F, Arcelli R, et al: Anatomical variation of of the radiopharmaceutical in damaged muscle groups can also aid the spinous and transverse processes in the caudal cervical vertebrae in the characterization of myositis or large muscle tears. and the first thoracic vertebra in horses. Equine Vet J 48:45-49, 2016. Magnetic resonance imaging (MRI) is the gold standard 3. Hughes KJ, Laidlaw EH, Reed SM, et al: Repeatability and technique for the central nervous system. Major limitations exist intra- and inter-observer agreement of cervical vertebral sagittal precluding the common use of this technology in adult horses. diameter ratios in horses with neurological disease. J Vet Intern Med When possible, MRI provides detailed information about the spinal 28:1860-1870, 2014. cord parenchyma, nerve roots and dura, the intervertebral disc, the 4. Janes JG, Garrett KS, McQuerry KJ, et al: Comparison of osseous structures including the vertebral bodies and processes and magnetic resonance imaging with standing cervical radiographs for the joints of the articular processes. Several recent publications have evaluation of vertebral canal stenosis in equine cervical stenotic described the use of this technology in clinical cases and use this myelopathy. Equine Vet J 46:681-686, 2014. technology as a tool to advance the collective understanding of 5. Janes JG, Garrett KS, McQuerry KJ, et al: Cervical Vertebral vertebral canal stenosis and vertebral stenotic myelopathy.4-6 Lesions in Equine Stenotic Myelopathy. Vet Pathol 52:919-927, 2015. Major advances in x-ray based diagnostic imaging technologies 6. Mitchell CW, Nykamp SG, Foster R, et al: The use of have occurred recently. Computed tomography (CT) and other magnetic resonance imaging in evaluating horses with spinal ataxia. x-ray based, tomographic projection 3-D imaging (robotics) have Vet Radiol Ultrasound 53:613-620, 2012. been introduced into equine practice and will likely come into more common use. Large bore conventional CT scanners (Philips Big Bore, Samsung BodyTom) can accommodate adult warm blood horses to the level of the cranial thoracic spine, depending on table configuration. Robotic imaging is in its infancy but will theoreti- cally provide large part cross sectional imaging in the standing, sedated horse. CT scanning provides excellent information about

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Enhancing Your Radiographic Technique Sarah M. Puchalski, DVM, DACVR Circle Oak Equine Sports Medicine, Petaluma, CA

• Digital imaging has improved the capabilities hoof and sole. When making foot radiographs, consider packing of equine practitioners material for the sulci of the frog. • Digital radiographs introduce many opportunities Each radiograph is one component of a complete examination along with novel pitfalls and a one-view study is almost always inadequate for assessment of • Artifacts of acquisition: digital artifacts, processing, any region. Each radiograph should be made keeping patient positioning can lead to misdiagnosis positioning with respect to beam center and angle in mind. The • Opportunities are afforded by: digital image individual horse should be assessed for limb conformation in order transfer, teleradiology and ease of consultation to determine beam angle and center. For example, is the horse toed with specialists out, or does it have fetlock varus, does it have a straight hock? These conformational abnormalities will dictate beam angle at the time of acquisition. Positioning aids such as blocks to position the INTRODUCTION front feet in an even weight bearing position or to house the The common use of digital diagnostic radiography in equine detector while the horse stands on the ‘tunnel’ remain critical tools practice has opened a world of opportunities and challenges with for the acquisition of good quality radiographs. regards to image quality, interpretation, medical record keeping, Exposure factors were a critical factor with film screen image transfer and storage. radiography and most digital systems have a much greater margin of error. However, exposure factors still influence image quality. IMAGE QUALITY Underexposure results in grainy images or images with poor signal In the day when the specific cost per radiograph could be to noise ratio that can render the image of lesser diagnostic quality calculated and double exposures or patient motion were not even if the ‘brightness’ is reasonable. Overexposure can result in identified until returning to the radiograph processor, it is arguable clipping artifact whereby thin anatomy or the soft tissues are that practitioners took greater care in the preparation for and ‘clipped’ from the image. Meaning, the trochlear ridges for example acquisition of field radiographs. With the widespread use of DR are not recorded in the digital images. They are not visible and systems, repeating radiographs has a much less tangible cost then it cannot be recovered through digital enhancement techniques. once did. This is a great advantage in almost all situations, however, Digital markers are frequently inadequate. Most digital every practitioner should reflect upon the tenets of quality radio- radiography systems do not ‘require’ than an external radiopaque graph production prior to commencement of radiograph acquisi- marker be applied to the detector at the time of acquisition. It is tion. One must pay attention to patient preparation, positioning, strongly recommended that metallic markers still be used in a exposure factors, beam center and angle, collimation, distance from manner consistent with traditional radiography. The marker the generator to the subject and from the subject to the detector. should denote left versus right, front versus hind and be projected Patient preparation should include assessment of the physical to the lateral or the dorsal aspect of the anatomy being imaged. area for equipment set-up, patient restraint including the use of Radiation safety should be of great concern to equine practi- sedation, the limbs should be clean and dry and the hoof prepared tioners. Most digital systems require higher exposure factors than by removal of the shoe (when possible) and trimming of excess film screen combinations. The greatest increase in radiation

The Clinician 39 THE CLINICIAN SUMMER 2018 exposure to equine practitioners is the frequent re-takes and the INTERPRETATION common attempts to radiograph large parts. Repeating radio- ‘You must know where to look and what to look for’ says Dr. graphs is a clear example of doubling or tripling the dose. Large Tim O’Brien father of modern equine radiology. This adage part radiography requires very high exposure factors, long exposure remains true. Understanding the anatomy and the anticipated times, hand holding the generator and large amount of scatter pathology is critical to accurate assessment of radiographs. radiation coming back towards the person taking the radiograph Digital imaging is also fraught with another set of complicat- and the holder. Decreasing exposure time, increasing distance from ing factors than can impact accuracy in interpretation. Image the radiation and shielding remain the most important factors in quality should be maximized and artifacts minimized. Image radiation safety to recall at the time of radiograph acquisition. interpretation should be performed in an appropriate environment Artifacts play an important role in digital radiography. Some on a computer monitor of adequate quality. A viewing station artifacts such as motion manifest similar to film screen as image located in an area with controlled, indirect ambient lighting is blurriness. Other artifacts are specific to digital technologies. critical. Monitors should be 3-5megapixel for medial image Artifacts related to equipment malfunction or damage can be interpretation. This is not always possible and in order to work varied and must be recognized on a case-by-case basis. Equipment around a lower quality laptop image, the observer should use the care (cords, connections, detector surfaces, tunnels) is critically digital tools available through viewing software. Artifacts associat- important. Artifacts associated with processing can be more ed with digital image processing should be recognized as such. difficult to identify and manage. Edge enhancement is one example Digital displays have lower luminance (brightness) than view that can result in overshoot artifact or a crisp black line running boxes and radiographs. Monitors with high luminance and large parallel to high-density surfaces such as cortical bone or metal. contrast ratios are best. However, low luminance is a contributor to This artifact can mimic fracture lines or render it impossible to observer fatigue. General fatigue is also a contributor to observer assess metallic implants in bone for peri-implant lysis. fatigue as seen during image interpretation. Fatigue will result in

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longer times to make a decision and decreased accuracy in lesion StateAndLocal/Pages/sr-confidentiality-patient-records.aspx). identification and assessment. Furthermore, bias, in various forms, Digital image storage and transfer has opened up the industry can also play a role in inaccurate image interpretation. For of veterinary consulting. Easy image transfer has facilitated the example, a known relatively common bias is something called global industry of horse sales and allowed for easy access to ‘satisfaction of search’ whereby the viewer finds a lesion of impor- diagnostic imaging consultants, and allows veterinarians to monitor tance for the clinical picture and overlooks smaller or unrelated and manage their patients when the are away from home. Many (often important) other lesions. digital management products are available to facilitate transfer between veterinarians, between veterinarians and clients. Small IMAGE MANAGEMENT clinics and solo practitioners can easily add veterinary specialists to Digital file management is a challenge for all health care their team regardless of location, thereby improving the products professionals. Diagnostic imaging file management is further and service they can provide and potentially improving patient care complicated by the large size of the individual files, most notably and outcome. radiographs. Digital Imaging and Communications in Medicine or DICOM is a standard for medical image files. This format, in SUMMARY general, preserves the size of the original image with the DICOM Digital diagnostic imaging presents opportunities and chal- header information that includes patient name, date of birth, lenges that did not previously exist. Understanding the technolo- equipment, clinic, date of acquisition and other critical informa- gies and potential pitfalls aid in the interpretation of images tion. This information can be retrieved from any DICOM file in an ultimately improving the quality of service and patient care. Digital appropriate viewer. These files tend to be very large (5-10MB per imaging poses challenges associated digital file management that radiograph) and unwieldy and generally speaking, difficult for can also be views as great opportunities for opening doors to clients to view. However, they are secure and stable and allow for outside consultation and opinions. accurate transmission of the meta-data from one observer to another. No other file format should be considered adequate for diagnostic evaluations. Image storage and ownership reflect the rules laid out histori- cally for radiographs. In California, the radiographs should be kept for 3 years and remain the property of the veterinary facility that originally made them. Radiographs should have permanent identification that includes the hospital, client, patient, and date the radiographs were made. Radiographs can be transferred from one to another veterinarian upon authorization by the client. Long term and secure options for image storage are available through many sources including many different cloud based servers in addition to hardware kept onsite. A solution for each clinic / practitioner exists, but there will be a cost associated with most options. When stored as DICOM images, if the information was accurately input at the time of acquisition (usually before the study is closed) the requirements for labeling should be included. Image transfer is an important, often complicated problem. Legally, image transfer should go from the clinic making the study to another veterinarian only with consent of the client. This is very easily managed at the point of first transfer. What is less clear is how images are managed and permissions given after they are digitally released. With all things in a digital age, once they are out in the world, they are difficult or impossible to recall. More information can be found o the AVMA website (www.avma.org/Advocacy/

The Clinician 41 THE CLINICIAN SUMMER 2018 NEAEP

Is Nuclear Scintigraphy Still Alive? Sarah M. Puchalski, DVM, DACVR Circle Oak Equine Sports Medicine, Petaluma, CA

• Performance problems in the sport horse have beam CT, and cone beam x-ray technology combined with robotics many different presentations and flat panel detectors. • Accurate diagnosis critical As a general rule, all diagnostic imaging modalities add • Scintigraphy is an important diagnostic and information to any work up, the question becomes whether or not management tool that information is adequate to identify and define the important abnormalities and fully characterize the problem at hand. Further- INTRODUCTION more, most of the modalities have very specific limitations that may make the choice clear. Logistics and physical limitations may limit As our knowledge of equine sports medicine advances the list the practical choices but notwithstanding these aspects, the choices of differential diagnoses causing performance problem lengthens. should be made with an understanding of the method of acquisi- A careful and thorough clinical examination, including static and tion of the imaging modalities. dynamic manipulation, diagnostic aids for assessment of locomo- tion, diagnostic anesthesia and diagnostic imaging techniques are all important components in the evaluation of horses with lower NUCLEAR SCINTIGRAPHY than expected performance. In some instances ‘the problem’ can be Racetrack and sport horse practitioners have good familiarity distilled down to a single pathologic entity and in these situations with this technique and there is a good and lengthy history of litera- one should consider oneself lucky. More often than not, the adult ture documenting its clinical utility. This technique requires sport horse is a complicated interaction of different problems of specialized facilities with appropriate licensing, trained personnel variable importance. These abnormalities may even arise from and is moderately expensive. The horses must be housed in different body systems. For example, many sport horses will have licensed facilities with proper disposal of their waste (bedding, lameness in more than one limb, or lameness in one limb in urine and feces) until the horse’s radioactivity decays to a safe addition to axial skeleton dysfunction. Diagnostic imaging is an (legal) level. important piece of a complete work up that can be overwhelming The radionuclide (Technetium-99m) is attached to a phos- to sort through. In choosing an advance imaging technique, logistic phate analogue, usually methylene diphosphonate (or hy- considerations are almost always a factor regardless of the horse’s droxymethylene diphosphonate). The radioactive component location and the owner’s budget. Which modalities are available decays, emitting gamma rays that are captured by the gamma when and how far away? How does the show / competition camera and used to form an image. The MDP binds to hydroxyap- schedule influence availability? Is there a budget? Should one atite crystals in bone matrix or in mineralizing soft tissues. Thus, problem be prioritized over another? together they provide localization of radiopharmaceutical at sites of Currently, many advanced diagnostic imaging modalities are increased bone turnover. This is seen in normal and pathologic available and several more are visible on the horizon. Nuclear processes and the interpretation of scintigraphy images hinges on scintigraphy, magnetic resonance imaging, and computed tomogra- knowledge of normal patterns of uptake. The timing of image phy are mainstay techniques that have seen great advances. Novel acquisition relative to the time of injection of the radiopharmaceu- modalities include newer nuclear techniques (PET scanning), cone tical determines the focus of the study.

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Scintigraphy, in the way that it is commonly performed in gamma rays to differentiate the lesion from background. Overall equine practice, can be evaluated during three time frames. skeletal metabolism and body size heavily influence the ability to Vascular phase images are made to demonstrate blood flow in detect lesions. Young horses and horses in training with very active vessels. Vascular images are challenging to acquire because images bone metabolism image better than older horses. Thin horses must be made in a dynamic fashion (one frame every second or image better than fat horses. Blood flow to the extremities, every other second) while the pharmaceutical is intra-vascular commonly diminished in cold climates, also influences uptake. (0-3min after injection). This can be useful for certain rare clinical Thus an older, fat Warmblood that has not been in work, imaged conditions such as vascular thromboembolus. Soft tissue images in the middle of winter will provide the lowest amount of are slightly less particular but still require images to be made within discernable uptake. minutes of injection. Soft tissue abnormalities, when identified, are Nuclear scintigraphy is excellent for certain clinical scenarios. dependent on extravasation of the radionuclide into the interstitial Horses, particularly younger horses, with stress induced or training space or hyperemia of the injured tissue. The pooling of the related skeletal remodeling image very well with this technique, radiopharmaceutical is transient and can be confusing to interpret allowing for the identification of lesions in multiple limbs or in the due to overlapping with late vascular phase and early bone phase axial skeleton. This applies not just to the racehorse but also to uptake. Furthermore, the emitted radioactivity is attenuated in young Western performance horses and Warmblood sport horses tissue with half of the radioactivity being attenuated every 7cm of alike. In these situations, multiple limb lameness, poor perfor- tissue. Thus, soft tissue phase imaging (relatively low uptake) is mance, decreased enthusiasm for work, or a lameness that cannot best limited to peripheral or superficial soft tissue regions. General- be localized by diagnostic anesthesia may be present. Bone phase ly speaking, soft tissue scanning of large parts such as the back, scintigraphy also provides incredibly useful information for pelvis or stifles is of limited value. Serious muscle injury, tears or lameness conditions that are localized but are associated with exertional rhabdomyolysis are often demonstrated on delayed or minimal or no radiographic or ultrasonographic findings. For bone phase images due to pooling of radiopharmaceutical in the example, lameness localized to the fetlock region with a low four torn or damaged muscle tissue. point nerve block with normal radiographs may show up as Lesion detection on bone or delayed phase scintigraphy is marked subchondral bone remodeling, likely training related, in dependent on the gamma camera ‘seeing’ an adequate amount of both race horses and sport horses.

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Nuclear scintigraphy is very good for certain complicated INTERPRETATION OF RESULTS clinical scenarios. In the adult sport horse, the horse in which we Nuclear scintigraphy, MRI and CT provide an incredible expect pathology to accumulate in multiple sites, scintigraphy can amount of information. The quantity of information can be yield important information about the whole horse that would overwhelming to both the veterinarian and the horse owner. Careful otherwise be difficult or impossible to garner. For example, a consideration of the findings with the clinical examination must be fourth level dressage horse with osteoarthritis in the neck, fetlocks, undertaken in order that the information is used to its fullest extent hocks, and sacroiliac joints and mild dorsal process impingement. but not over interpreted. Without interpretation relative to the In some instances, scintigraphy can be arguably used as tool to clinical picture, horses can be unfairly labeled as unfit or unsound. It tweak management of upper level performance horses. can be useful to divide the imaging findings into major and minor Nuclear scintigraphy is a critical component of axial skeleton findings and to assess etiopathogenesis (as best as current knowledge and large part imaging. Because of the limitations presented by the allows) and chronicity of the lesions. Major findings should be large size of the horse, scintigraphy, an emission imaging technique treated respectfully regardless of their present clinical significance. is an important element in evaluation of the upper portions of the Degenerative lesions may warrant different consideration than a appendicular and the axial skeleton. For example, pelvis or lumbar tissue that is torn due to supraphysiologic forces. spine evaluation is very difficult or impossible with routine radiographic techniques. Furthermore scintigraphy can be used to further clarify or assess the significance of radiographic abnormali- COMBINATION OF TECHNIQUES Multiple techniques, used in parallel or in series can provide ties. For example, marginal sclerosis as identified on radiographs of important complementary information that increases the overall the dorsal spinous processes of the thoracic spine can be of highly diagnostic yield for the patient and compensates for the shortcom- variable significance. Scintigraphy can be used to assess the current ings of each techniques. For example, computed tomography will level of active remodeling, a feature that may be useful in the not identify the so-called bone contusion or edema. However, CT assessment of the radiographs. will identify bone trauma including very small, incomplete Nuclear scintigraphy is a good screening test. In general, fractures. Both scintigraphy and MRI can provide information that screening tests should have high sensitivity with variable specificity. will complement the detail provided by CT. Scintigraphy will show In order to categorize the (diagnostic) test (high versus low if and demonstrate how pronounced the regional remodeling. MRI sensitivity or specificity) the abnormality for which it is testing of the same region may show intra-osseous fluid accumulation that must be qualified. For example, is the test sensitive for the identifi- provides similar but slightly different information that scintigraphy. cation of tarsal bone remodeling? Thus, in the way that scintigra- phy is commonly used in equine practice, it is screening for any number of different abnormalities, at many anatomic sites, of SUMMARY variable incidence within the population. In some clinical condi- All modalities provide information about the musculoskeletal tions, scintigraphy has lower sensitivity but actually a high level of system that can be useful to the assessment of the equine athlete. specificity. For example, the hind proximal suspensory attachment, Logistical and monetary constraints play a big role in the decisions this site that is often normal even in horses with proximal suspen- made in equine veterinary practice. Trade-offs exist for every sory pain and lameness (false negative). However, when the decision. An open discussion with an imaging specialist prior proximal, plantar third metatarsal bone has abnormally increased choosing a technique may be the best way to insure the best uptake, it is a very important and specific finding that confirms outcome for your client. proximal suspensory desmopathy / enthesopathy. Similarly, uptake in the medial femoral condyle is rare but when present, is most often associated with medial femoral condyle or medial femorotibi- al joint pathology.

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