Parasite Control On Thoroughbred Studs Thesis submitted in accordance with the requirements of the University of Liverpool for the degree of Doctor of Philosophy by Cara Louise Hallowell-Evans. June 2017 Author’s Declaration Apart from the help and advice acknowledged, this thesis represents the unaided work of the author ……………………………………………………………………………. Cara Hallowell-Evans June 2017 This research was carried out in the Department of Infection Biology and School of Veterinary Science, University of Liverpool i Acknowledgements I would like to begin by thanking the Horserace Betting Levy Board, especially Annie Dodd, for their support of this project financially and of me as a scholar. This incredible opportunity has developed me in so many ways, including allowing me to achieve both personal and professional goals, from writing for Horse & Hound to speaking at an international conference. I would like to express my sincere and unending gratitude to my supervisory team: Dr Jane Hodgkinson, Professor Jacqui Matthews and Professor Debbie Archer. Each have provided me with unique support and guidance, being consistently generous with their time and expertise. Jane especially has devoted an enormous amount of time, knowledge and patience to make this project a success. My thanks also go to the staff at the Moredun Research Institute who provided my training; my advisory team, Professor Diana Williams and Dr Nick Evans for their support and advice; Jan van Dijk and Gina Pinchbeck for their statistical guidance and the Donkey Sanctuary for providing samples. Thank you all so much – I am, as always, proud to have been a part of the University of Liverpool. In completing this work I have come to the firm, and evidence-based, realisation that no one is an island. There are countless other people without whom this work would not have been completed and I would not be where I am today. The expansive list of those others whose names should join mine on the cover begin with the stud vets, owners, managers and staff involved in all aspects of this project. I would like to express my heartfelt gratitude to you for your support, countless hours of sampling and liaising about test-and-treat plans, as well as explaining the vast lexicon of industry-specific terms and TB breeding ins-and-outs over coffee and cream-cake (special thanks to Jeanette and Tom). I have the utmost respect for your knowledge, skill, drive and the passion and dedication you show towards the sport and your horses. You are the driving force for this work and an inspiration to us all. Next are the fantastic Infection Biology group whose friendship, advice, moral and technical support, stats and R help, tolerance of “Rave Lab”, cake days and all-around overwhelming loveliness has been essential. In no particular order these amazing colleagues and friends, both past and present, are: Nicola, John, Patrick, Alison, Stephan, Juriah, Laura, Tess, Corrado, Christina, Paul, Jill, Charlie and, the undisputed queen of the lab, Catherine Hartley. Thank you all so much!!! Many more names should be on this list, I hope that those I have forgotten will accept my apologies and sincerest thanks. In moving to my next (ad)venture, I have had the pleasure of becoming part of the Reaseheath Animal Management family, who have made me feel truly at home. Over the past year, you have accepted me – indelicacy, wildness, peculiarities and all - with open arms, always encouraged me and made sure I’ve kept what little sanity I arrived with! Again, in no particular order, my unending thanks go to: Dan, Sarah, Lisa, Kate, Heather, Jordan, Val and the rest of the Animal Management and Canine teams. Special thanks are necessary, but nowhere near sufficient, for Elaine – who has urged me on, lightened my ii workload and supported me wholeheartedly while asking for nothing in return. Thank you all so much for your support and, most importantly, your phenomenal sense of humour - which has kept me laughing through the highs, lows and everything in-between! I adore you all. My thanks also go to Zoe and Sally who have supported me through many things from my first job as a new graduate to broken bones and career changes. All of my clinical knowledge and super-adaptable practical skills I owe to you. I am eternally grateful for your continued support, help and friendship. Last but definitely by no means least I would like to thank my incredible family. My parents, Rosanne and Roy, who put up with my juvenile delinquency to this day, show unshakeable faith and support for all of my endeavours – however bizarre! You are amazing and always inspire me to keep reaching for the stars. To my fabulous sister, Gayle, I extend my sincerest and most profound gratitude for your guidance, help and support. I am, as always, in awe of you. Lastly is Craig, my amazing and extremely long-suffering husband – it has been a roller coaster of a ride as always! You have endured this journey with me, providing love, support and grounding when I needed it most. I am, as always, so grateful to have you by my side and couldn’t have done it without you. I consider myself extremely lucky to have had this opportunity, although my dad would say that you make your own luck in life. Be this as it may, the help and support of superiors, colleagues, friends and family is what pushes us to make the most of each chance we are given…and allows us to have fun with it along the way! Thank you all so much. iii Abstract Parasite Control on Thoroughbred Studs Cara Hallowell-Evans Gastrointestinal parasite infections impact on the health and welfare of Thoroughbreds (TB). The parasites of concern include the strongyles; cyathostomins and Strongylus vulgaris, Parascaris equorum and Anoplocephala perfoliata. In addition, there is increasing recognition of liver fluke infections in horses. Life-long parasite control is needed and use of anthelmintic drugs is the major approach, but decades of intensive anthelmintic usage has promoted widespread resistance particularly in cyathostomins and Parascaris equorum. Intensive anthelmintic usage is defined as the administration of an anthelmintic drug at set intervals, based on the original egg reappearance period (ERP) of the pioneer product, with the aim of egg output suppression; following the recognition and widespread nature of anthelmintic resistance targeted selective treatment regimens are now being advocated. Targeted selective treatment is defined by the American Association of Equine Practitioners (AAEP) as basing treatments during high transmission periods on diagnostic testing and identification of high egg shedding individuals in order to reduce pasture contamination while leaving a parasitic population in refugia, due to the current limitations in detection whole herd moxidectin and praziquantel treatments are still advocated annually as a minimum, with frequency dependent on a risk analysis and utilisation of available assays. The aim of this project was to identify parasite control practices on UK TB studs, determine drug efficacy on a subset of TB studs and evaluate the diagnostic potential of faecal diagnostic tests. Faecal diagnostic tests for F. hepatica and A. perfoliata were examined. A McMaster-based short method for F. hepatica was applied to known positive donkey (n=18) and horse (n=1) samples which were simultaneously evaluated with the standard sedimentation method. Mean egg per gram (epg) count was 21.0epg (0.2-138epg) and 31.0epg (0.4-202epg) for the short method and standard sedimentation, respectively. The centrifugal flotation (CF) method was investigated for detection of A. perfoliata eggs and compared to the validated double sugar flotation (DCF) test. In total 140 samples were tested. Of these, 25.7% (±7.2%, n=36/140) tested positive using CF and 22.1% (±6.9%, n=31/140) using DCF. Nine TB studs have undergone drug efficacy testing based on their anthelmintic use, control strategies and clinical disease concerns, mebendazole was tested on one stud, pyrantel on five studs; ivermectin on three and moxidectin on two. Tests were conducted for adults and youngstock independantly. The CF faecal egg count (FEC), sensitive to 1epg, was used to detect strongyle-type, Parascaris spp and A. perfoliata eggs. On studs where >10 animals showed >50epg (strongyle), faecal egg count reduction tests (FECRT) were performed to determine resistance status. ERP was defined as when group arithmetic mean FEC post-treatment exceeded 10% of group FEC arithmetic mean pre-treatment. Larval culture and morphological identification of strongyle third-stage larvae were also performed. On stud B, youngstock [YS] (n=7) PYR efficacy was 98.5% (97.9-99.0%), ERP = 3 weeks, and 93.2% (91.9-94.3%) in mares (n=8), ERP = 4 weeks; stud D only YS (n=31) showed resistance to PYR (reduction = 58.8% (57.6-60.0%)), sensitivity to IVM (100.0% (99.9-100.0%)) but borderline efficacy to MOX (94.5% (93.9-95.1%); ERP 4 weeks); stud F showed PYR resistance (n=23 YS, n=13 mares) with 0.1% (0.0-0.7%) and 69.5% (67.0-71.8%) reductions, IVM and MOX efficacy were 100.0% (99.9-100.0%) but ERP shortened to 6 iv weeks (IVM) and 8 weeks (MOX) in YS; stud G YS showed PYR resistance (n=18, 67.5% (64.9-69.9%) reduction). One stud (stud E) was referred to the project due to high levels of tapeworm-related disease in broodmares (~60-70% of mares affected per year). All stock were tested using the CF and DCF faecal methods and University of Liverpool (UofL) serum ELISA (adults, n=86; YS, n=64). For adult stock 74.4% (±9.7%, n=58/78) recorded negative A.