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Exercise induced pulmonary haemorrhage (EIPH) or ‘bleeding’ is an important disease of exercising horses. Though it is a disease commonly identified by equine veterinary practitioners, there is a lack of information regarding the impact of an episode of EIPH to career after examination or whether occurrence of EIPH is predictive of a horse’s lifetime athletic potential. There also exists a lack of consensus as whether the commonly used treatment, frusemide (a loop diuretic) is an effective medication to reduce or prevent EIPH. This research project addresses these two questions, with the aim of producing high quality information which can be used to underpin evidence based clinical recommendations for EIPH in horses.

BACKGROUND: Warmblood Fragile Foal Syndrome Type 1 (WFFS) is an autosomal recessive disorder reported previously only in warmbloods and thought to be caused by a variant in the gene procollagen-lysine,2-oxoglutarate 5-dioxygenase 1 (PLOD1, c.2032G>A, p.Gly678Arg). Given the presentation of this Thoroughbred case, we hypothesised that a similar genetic mechanism caused this phenotype. OBJECTIVES: To describe the pathological and genetic findings on a foal presenting to a veterinary practice in the UK with skin lesions similar to other Ehlers-Danlos Syndromes, including those documented for warmbloods with WFFS. STUDY DESIGN: A single case report describing a genetic investigation. METHODS: A Thoroughbred foal presenting as dystocia was euthanised for multiple skin lesions and developmental abnormalities. DNA extracted from the foal was tested for the PLOD1 variant (c.2032G>A, p.Gly678Arg) using the commercially available assay. To confirm causality and further interrogate potential novel causes of Ehlers-Danlos Syndrome, 1799 functional candidate genes, including PLOD1, were analysed using whole genome sequencing data generated from DNA extracted from the foals muscle. These data were compared to 34 control samples from at least 11 other breeds. Variants were prioritised for further evaluation based on predicted impact on protein function. RESULTS: Post-mortem evaluation concluded that this foal suffered from a condition of collagen dysplasia. The foal was homozygous for the c.2032G>A PLOD1 variant. Only two other missense variants identified from whole genome sequencing data were also computationally predicted to be deleterious to protein function, (NPHP3 c.1253T>C, p.Leu418Pro, EPDR1 c.154G>C, p.Glu52Gln). Neither of these genes have been linked to similar phenotypes, or Ehlers-Danlos Syndrome in humans or other species and thus further investigation of these variants as the cause of EDS was not warranted. MAIN LIMITATIONS: This study is a single cas

Bone and joint injuries in Thoroughbred racehorses typically originate in areas of intense loading and are attributable to fatigue damage accumulated under repetitive cyclical loading. This thesis will focus on an epidemiological understanding of the bone fatigue process as it relates to Thoroughbred training and racing. Factors investigated include workload, stride parameters, speed and distance worked. Specifically, this included an investigation of racehorse management, training and rest compared to previously published risk factors and how they relate to performance, stride characteristics of galloping horses during racing and how varying strides and race factors influence the estimated accumulation of bone damage over race starts. It was hypothesised that (i) there would be a large variation between trainers in the training and rest practices; (ii) greater workloads in training would not be associated with superior race performance; (iii) speed would be correlated with stride parameters, increasing proportionally more with stride duration than the number of strides (and therefore stride length) at higher speeds; (iv) stride parameters would differ by horse-and race-level factors; and (v) a higher percentage of bone fatigue life would be used for longer distance races, firmer track surfaces and higher classed races. These hypotheses were investigated by conducting a semi-structured in-person interview of 66 registered Thoroughbred trainers in Victoria, Australia; by analysing GPS and accelerometer data including speed and stride data from 25,245 Thoroughbred race starts in Tasmania, Australia; and by generating a mathematical model of bone fatigue accumulation using information from the stride parameter data. Australian Thoroughbred training programs include high volumes of galloping with more than half exceeding previously reported risk levels for fracture. Older age and longer intended race distances were associated with higher galloping workloads, and there w

Bone and joint injuries in Thoroughbred racehorses typically originate in areas of intense loading. Despite the increasing understanding regarding the pathogenesis of bone fatigue, early detection prior to fatigue fracture is difficult. This thesis focuses on understanding equine behaviour and its potential to reflect orthopaedic pain to assist in the early identification of horses at risk of injury. Previous research suggests an association between facial expression and the presence of equine lameness. In cattle, motion sensors have been validated to record recumbency behaviour used to detect disease without the need for continuous observation. This thesis aimed to investigate monitoring of behavioural patterns as predictors of injury in racehorses. In the first study, Thoroughbred racehorses were monitored at rest with motion sensors placed on forelimbs. Sensor data was collected, and an algorithm developed to identify certain behaviours. Algorithms were validated through video observation and calculation of algorithm sensitivity and specificity. There was excellent agreement for standing, lying, and for stepping behaviour patterns suggesting potential for long term, objective, remote monitoring of horses in the stable environments. In the second study, previously validated facial grimace scales were used to score pain from photographs of Thoroughbreds, captured from video recordings during trot up examinations. This method demonstrated horses with moderate mouth strain (HGS) and tense and extended upper lip (FEReq) were associated with horses less likely to be lame. Exposed sclera was associated with lameness in hand, at the trot. Cohen's kappa was used to measure the proportion of agreement between raters, with behaviours scored to more than two categories the kappa was ordinal weighted. Mean inter observer agreement was moderate, and the sum of facial scores showed no difference between lame and sound horses. There were few associations between lameness status

Genom avel har hästar anpassats till olika syften ända sedan de domesticerades av människan. Detta har bl.a. resulterat i att hästar av olika raser skiljer sig i sin muskelfibersammansättning. Idag används hästar främst i sportsammanhang t.ex. galopptävlingar och dressyruppvisningar. Syftet med studien var att få en ökad kunskap och förståelse för musklernas uppbyggnad och ta reda på hur skillnaden i muskelfibersammansättning ser ut mellan dressyrhästar och galopphästar. I denna litteraturstudie har raserna fullblod och andalusier studerats och jämförts, genom ett t-test, då de är vanligt förekommande i de nämnda grenarna. Hästars skelettmuskler består av muskelfibrerna; typ I, typ IIA och typ IIX. Fibrerna producerar energi på olika sätt och beroende på intensiteten och varaktigheten av arbetet rekryteras fibertyperna efter olika mönster. Andalusier har högre andel typ I fibrer jämfört med fullblod. De förlitar sig därför mer på aerob energiomsättning. Andelen typ IIA fibrer var lika mellan raserna men andelen typ IIX skiljer sig då fullblod har visats ha en högre andel. Fullblod förlitar sig både på aerob och anaerob glykolys. Skillnader i fibersammansättning finns hos de olika raserna även om de inte genomgått någon träning., Horses have been bred for different purposes ever since the human domesticated them. As a result of that, horse breeds differ in their muscle fibre composition. Today, horses are used mainly in sports like horse racing and dressage shows. The aim of the study was to get more knowledge and understanding about the muscles composition and learn how the muscle fibre composition differs between dressage horses and racehorses. In this literature study, the breeds Thoroughbred and Andalusians have been studied and compared, with a t-test, since they are common breeds in the mentioned sports. Horse skeletal muscles consist of the muscle fibres; type I, type IIA and type IIX. The fibres produce energy either anaerobically or aerobically and depending on the intensity and duration of the work, muscle fibre recruitment differs. Andalusians have a higher amount of type I fibres compared to Thoroughbreds. They rely therefore more in aerobic glycolysis as an energy source. The amount of type IIA was the same between the breeds but the concentration of type IIX differed and the Thoroughbred had a higher amount. Thoroughbreds rely both in aerobic and anaerobic glycolysis. There are differences in muscle fibre composition between different breeds even if they haven’t gone through any training.

De paardenfokkerij in het Verenigd Koninkrijk heeft een lange en boeiende geschiedenis, die teruggaat tot de vroege Middeleeuwen. De paardenraces, in de vorm zoals we die vandaag de dag kennen, begonnen in de 16e eeuw in Engeland. Het jaar 1678 wordt algemeen erkend als het jaar dat met de fok van het moderne volbloedpaard werd gestart. Rond dezelfde tijd werden om reden van nationale veiligheid de eerste wetten ingevoerd, gericht op het verhogen van de kwaliteit van het Britse paard en om de uitvoer van de beste paarden te verbieden.

Cytotoxic T-lymphocytes (CTLs) are associated with protective immunity against disease caused by equid herpesvirus type 1 (EHV-1). However, the EHV-1 target proteins for CTLs are poorly defined. This limits the development of vaccine candidates designed to stimulate strong CTL immunity. Here, classical CTL assays using lymphocytes from horses of three defined MHC class I types that experienced natural infection with EHV-1 and a modified vaccinia virus construct containing an EHV-1 gene encoding the immediate-early (IE) protein are reported. Horses homozygous for the equine leukocyte antigen (ELA)-A2 haplotype, but not the ELA-A5 haplotype, produced MHC-restricted CTL responses against the IE protein. Previously, horses homozygous for the ELA-A3 haplotype also mounted CTL responses against the IE protein. Both haplotypes are common in major horse breeds, including the Thoroughbred. Thus, the IE protein is an attractive candidate molecule for future studies of T-cell immunity to EHV-1 in the horse.

Identification of risk factors which are associated with severe clinical signs can assist in the management of disease outbreaks and indicate future research areas. Pregnancy loss during late gestation in the mare compromises welfare, reduces fecundity and has financial implications for horse owners. This retrospective study focussed on the identification of risk factors associated with pregnancy loss among 46 Thoroughbred mares on a single British stud farm, with some but not all losses involving equid herpesvirus-1 (EHV-1) infection. In a sub-group of 30 mares, association between pregnancy loss and the presence of five common Thoroughbred horse haplotypes of the equine Major Histocompatibility Complex (MHC) was assessed. This involved development of sequence specific, reverse transcriptase polymerase chain reactions and in several mares, measurement of cytotoxic T lymphocyte activity. Of the 46 mares, 10 suffered late gestation pregnancy loss or neonatal foal death, five of which were EHV-1 positive. Maternal factors including age, parity, number of EHV-1 specific vaccinations and the number of days between final vaccination and foaling or abortion were not significantly associated with pregnancy loss. In contrast, a statistically significant association between the presence of the MHC class I B2 allele and pregnancy loss was identified, regardless of the fetus / foal’s EHV-1 status (p=0.002). In conclusion, this study demonstrated a significantly positive association between pregnancy loss in Thoroughbred mares and a specific MHC class I allele in the mother. This association requires independent validation and further investigation of the mechanism by which the mare’s genetic background contributes to pregnancy outcome.

Cytotoxic T-lymphocytes (CTLs) are associated with protective immunity against disease caused by equid herpesvirus type 1 (EHV-1). However, the EHV-1 target proteins for CTLs are poorly defined. This limits the development of vaccine candidates designed to stimulate strong CTL immunity. Here, classical CTL assays using lymphocytes from horses of three defined MHC class I types that experienced natural infection with EHV-1 and a modified vaccinia virus construct containing an EHV-1 gene encoding the immediate-early (IE) protein are reported. Horses homozygous for the equine leukocyte antigen (ELA)-A2 haplotype, but not the ELA-A5 haplotype, produced MHC-restricted CTL responses against the IE protein. Previously, horses homozygous for the ELA-A3 haplotype also mounted CTL responses against the IE protein. Both haplotypes are common in major horse breeds, including the Thoroughbred. Thus, the IE protein is an attractive candidate molecule for future studies of T-cell immunity to EHV-1 in the horse.

Hepatitis C virus (HCV) causes chronic and acute liver diseases in humans. This virus’s origin is unknown, and many research works into the design of a prophylactic vaccine have been inhibited due to the lack of a tractable model, partly due to its narrow host range (humans and chimpanzees). Equine Hepacivirus (EqHV) in 2011 was discovered in respiratory samples of dogs and found to be the closest genetic relative to Hepatitis C virus (HCV). This virus naturally infects horses and has several similarities to HCV, ranging from delayed onset of seroconversion, persistent infection, and liver pathology, thereby making it a potential experimental model to study hepacivirus infections in their natural host. This study investigated the prevalence of EqHV among Thoroughbred racehorses. Polymerase reaction (PCR) assays were designed to detect and quantify this virus in 66 Thoroughbred racehorses’ serum samples. Approximately 38% of these horses were positive for the virus with a viral load range between 6.19 x 102 – 1.26 x 107copies/mL. Using retrospective sera samples sampled at different time points, we further investigated this virus’s infection profile among Thoroughbred racehorses. The results showed, similar to HCV that EqHV causes acute and chronic infections and that infected animals are susceptible to reinfection with varying seroreactivity degrees. Further analysis of these sera showed diversification of these viral populations among Thoroughbred racehorses. Also, multiple signatures of vector-borne transmission and immune-mediated selection of viral variants were observed. Optimisation of an EqHV entry assay utilising retrovirus pseudotypes was performed. The stability of these virus particles was also investigated.

Identification of risk factors which are associated with severe clinical signs can assist in the management of disease outbreaks and indicate future research areas. Pregnancy loss during late gestation in the mare compromises welfare, reduces fecundity and has financial implications for horse owners. This retrospective study focussed on the identification of risk factors associated with pregnancy loss among 46 Thoroughbred mares on a single British stud farm, with some but not all losses involving equid herpesvirus-1 (EHV-1) infection. In a sub-group of 30 mares, association between pregnancy loss and the presence of five common Thoroughbred horse haplotypes of the equine Major Histocompatibility Complex (MHC) was assessed. This involved development of sequence specific, reverse transcriptase polymerase chain reactions and in several mares, measurement of cytotoxic T lymphocyte activity. Of the 46 mares, 10 suffered late gestation pregnancy loss or neonatal foal death, five of which were EHV-1 positive. Maternal factors including age, parity, number of EHV-1 specific vaccinations and the number of days between final vaccination and foaling or abortion were not significantly associated with pregnancy loss. In contrast, a statistically significant association between the presence of the MHC class I B2 allele and pregnancy loss was identified, regardless of the fetus / foal’s EHV-1 status (p=0.002). In conclusion, this study demonstrated a significantly positive association between pregnancy loss in Thoroughbred mares and a specific MHC class I allele in the mother. This association requires independent validation and further investigation of the mechanism by which the mare’s genetic background contributes to pregnancy outcome.

Cytotoxic T-lymphocytes (CTLs) are associated with protective immunity against disease caused by equid herpesvirus type 1 (EHV-1). However, the EHV-1 target proteins for CTLs are poorly defined. This limits the development of vaccine candidates designed to stimulate strong CTL immunity. Here, classical CTL assays using lymphocytes from horses of three defined MHC class I types that experienced natural infection with EHV-1 and a modified vaccinia virus construct containing an EHV-1 gene encoding the immediate-early (IE) protein are reported. Horses homozygous for the equine leukocyte antigen (ELA)-A2 haplotype, but not the ELA-A5 haplotype, produced MHC-restricted CTL responses against the IE protein. Previously, horses homozygous for the ELA-A3 haplotype also mounted CTL responses against the IE protein. Both haplotypes are common in major horse breeds, including the Thoroughbred. Thus, the IE protein is an attractive candidate molecule for future studies of T-cell immunity to EHV-1 in the horse.

Identification of risk factors which are associated with severe clinical signs can assist in the management of disease outbreaks and indicate future research areas. Pregnancy loss during late gestation in the mare compromises welfare, reduces fecundity and has financial implications for horse owners. This retrospective study focussed on the identification of risk factors associated with pregnancy loss among 46 Thoroughbred mares on a single British stud farm, with some but not all losses involving equid herpesvirus-1 (EHV-1) infection. In a sub-group of 30 mares, association between pregnancy loss and the presence of five common Thoroughbred horse haplotypes of the equine Major Histocompatibility Complex (MHC) was assessed. This involved development of sequence specific, reverse transcriptase polymerase chain reactions and in several mares, measurement of cytotoxic T lymphocyte activity. Of the 46 mares, 10 suffered late gestation pregnancy loss or neonatal foal death, five of which were EHV-1 positive. Maternal factors including age, parity, number of EHV-1 specific vaccinations and the number of days between final vaccination and foaling or abortion were not significantly associated with pregnancy loss. In contrast, a statistically significant association between the presence of the MHC class I B2 allele and pregnancy loss was identified, regardless of the fetus / foal’s EHV-1 status (p=0.002). In conclusion, this study demonstrated a significantly positive association between pregnancy loss in Thoroughbred mares and a specific MHC class I allele in the mother. This association requires independent validation and further investigation of the mechanism by which the mare’s genetic background contributes to pregnancy outcome.