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EQUINE VETERINARY EDUCATION / AE / JANUARY 2017


information gained from the blood smear review could not be captured by looking at only the white blood cell or neutrophil count. The microscopic review of blood smears from critically ill horses to detect band cells or neutrophil toxic change is valuable and could help in assessing disease severity and prognosis in adult equine emergency admissions.


Osteochondrosis in yearlings


The aim of this study by John Russell and colleagues in Australia and the UK was to determine the prevalence and genetic variability of osteochondrosis (OCD) lesions in yearling Thoroughbreds in Australia. Pre-sales radiographs of 1962 yearlings over an 8-year


period were obtained from clinical records at one veterinary practice. Environmental conditions varied between farms. A standardised set of 34 radiographic views were examined by two experienced orthopaedic clinicians, who were blinded to the horse’s clinical history. The prevalence of horses with OCD in at least one joint


was 23%. Lesions were found in the stifle in 10%; the lateral trochlear ridge of the distal femur was the most common site (6%). Lesions in the proximal interphalangeal (fetlock) joints were present in 8%, mostly dorsoproximal P1 fragments. Lesions in the tarsus were found in 6%; the distal intermediate ridge of the tibia was the most common site (4%). Estimates of genetic variability were low with large


standard errors, meaning none was significantly different from zero. This suggests that nongenetic factors have a more important impact on development of OCD. The low importance of heritability in OCD in Thoroughbreds has also been reported in other studies. However, some OCD lesions were associated with the dam’s environment in this study, suggesting that mares’ nutrition, housing, age or other factors possibly contribute to OCD in their offspring.


Risk factors for deep stromal abscesses


In this investigation Laura Proietto and colleagues in the USA aimed to identify potential environmental risk factors for the diagnosis of equine deep stromal abscesses (DSA) in the subtropical climate in Florida. Cases were selected from the University of Florida


Veterinary Medical Center medical record and imaging database, and included all cases of equine DSA diagnosed during a 22-year period. Date of diagnosis and atmospheric data was obtained for north central Florida for the corresponding time period. Univariate and multivariate general linear models were generated testing effects and interactions between environmental conditions. When year, sulfur dioxide (SO2) and wind were analysed


in the presence of each other, a one-mile per hour increase in wind significantly increased the number of DSA cases by 1.63 cases per year. When the influence of temperature was evaluated in conjunction with year and nitrogen dioxide (NO2), the number of cases decreased by 0.1534 per year for every degree increase in temperature (°C). Wind speed is the first significant atmospheric risk factor to


be identified for DSA formation in the horse. The importance of environmental variance in the incidence of DSA indicates that the pathogenesis of DSA formation may be multifactorial, interdependent and provides support in some horses for the micropuncture hypothesis of DSA formation


© 2016 EVJ Ltd


related to the involvement of environmental conditions causing precorneal tear film and epithelial damage.


Racehorse fatal injuries in the USA and Canada


This retrospective study by Stamatis Georgopoulos and Tim Parkin from the University of Glasgow identifies risk factors associated with fatal injuries in Thoroughbred racehorses competing in flat racing in the USA and Canada. Data for 1,891,483 race starts by 154,527 Thoroughbred


racehorses at 89 racetracks in the USA and Canada (2009– 2013) were extracted from the Equine Injury Database. Forty- four possible risk factors were evaluated by univariate then multivariable logistic regression to identify those that were significantly associated with fatal injury (death or euthanasia of a horse within 3 days after sustaining an injury during a race). Fatal injury ended 3572 race starts (period incidence rate


1.9 fatal injuries/1000 race starts). Twenty-two risk factors were significantly associated with fatal injury. Risk of fatal injury was greater for stallions than for mares and geldings, and increased as the number of previous nonfatal injuries and race withdrawals and level of competitiveness (e.g. horse’s winning percentage and race purse) of the horse or race increased. The risk factors associated with fatal injuries in Thoroughbred racehorses identified in this study can be used to help identify racehorses at high risk of sustaining a fatal injury and in the design and implementation of preventative measures to minimise the number of fatal injuries sustained by horses competing in flat racing in the USA and Canada.


S. WRIGHT EVE Editorial Office References


Georgopoulos, S.P. and Parkin, T.D. (2016) Risk factors associated with fatal injuries in Thoroughbred racehorses competing in flat racing in the United States and Canada. J. Am. Vet. Med. Assoc. 249, 931-939.


Johnstone, L.K., Engiles, J.B., Aceto, H., Buechner-Maxwell, V., Divers, T., Gardner, R., Levine, R., Scherrer, N., Tewari, D., Tomlinson, J. and Johnson, A.L. (2016) Retrospective evaluation of horses diagnosed with neuroborreliosis on postmortem examination: 16 cases (2004– 2015). J. Vet. Intern. Med. 30, 1305-1312.


Knowles, E.J., Harris, P.A., Elliot, J. and Menzies-Gow, N.J. (2016) Use of the oral sugar test in ponies when performed with or without prior fasting. Equine Vet. J. Epub ahead of print; doi: 10.1111/evj.12607.


Lambert, J.L., Fernandez, N.J. and Roy, M.-F. (2016) Association of presence of band cells and toxic neutrophils with systemic inflammatory response syndrome and outcome in horses with acute disease. J. Vet. Intern. Med. 30, 1284-1292.


McConachie, E., Giguere, S. and Barton, M.H. (2016) Scoring system for multiple organ dysfunction in adult horses with acute surgical gastrointestinal disease. J. Vet. Intern. Med. 30, 1276-1283.


Proietto, L.R., Plummer, C.E., Maxwell, K.M., Lamb, K.E. and Brooks, D.E. (2016) A retrospective analysis of environmental risk factors for the diagnosis of deep stromal abscess in 390 horses in North Central Florida from 1991 to 2013. Vet. Ophthalmol. 19, 291-296.


Russell, J., Matika, O., Russell, T. and Reardon, R.J.M. (2016) Heritability and prevalence of selected osteochondrosis lesions in yearling Thoroughbred horses. Equine Vet. J. Epub ahead of print; doi: 10.1111/evj.12613.


VanDierendonck, M.C. and van Loon, J.P. (2016) Monitoring acute equine visceral pain with the Equine Utrecht University Scale for Composite Pain Assessment (EQUUS-COMPASS) and the Equine Utrecht University Scale for Facial Assessment of Pain (EQUUS-FAP): A validation study. Vet. J. 216, 175-177.


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