EQUINE VETERINARY EDUCATION / AE / MARCH 2016


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Highlights of recent clinically relevant papers


Risk. factors for injury in Swiss horse racing This retrospective study by C. Schweizer and colleagues in Switzerland aimed to evaluate the risk factors related to clinical injury in various horse racing disciplines in Switzerland. All race starts in flat, obstacle and trot racing over 4 years


were analysed. This included a total of 17,760 race starts in 1738 races at 10 racecourses. The age, sex, earnings, distance and time raced, place, jockey/driver, owner, trainer, track surface type and if grass, the surface conditions were recorded. Racetrack vets recorded clinical and nonclinical observations and recorded these with a standardised ‘Veterinary Code system’. At least one Veterinary Code was recorded for 525


horses: the most common was nonclinical one, i.e. Non- Starter. The highest incidence of Veterinary Codes was


associated with obstacle races (106/1000 starts), followed by flat races (27/1000) and then trot races (21/1000). Multivariable logistic regression models were used to


analyse risk factors in each discipline. Horses were more often recorded as fallen or pulled up in obstacle races than in other disciplines. Horses finishing over eighth place had a higher risk of clinical events than those placed 1–3in flat, obstacle and trotting races. In trot racing, gait abnormalities and lameness were the most common Veterinary Codes recorded and there was a lower risk of clinical events for runners on Porphyre sand than on grass. The risk was approximately doubled for those whose driver was also their trainer. The researchers speculated that this may be due to trainers feeling more able to take risks when driving their own horse. In flat racing, one racecourse had a higher risk of clinical


event than some of the others but no associations were found relating to the racecourse surface. Obstacle races of over 2401 m carried a lower risk of injury. The researchers pointed out that some confounding


factors may account for some of the associations found in this study, and that there is a need to improve the standardisation of event recording. However the study represents a positive initial step in identifying risk factors for racing injury that may allow steps to be taken towards prevention.


Predictor variables for strangles


In this retrospective case–control study, Lauren Duffee and colleagues in the USA evaluated predictor variables for and complications associated with Streptococcus equi ssp. equi infection (strangles) in horses. Medical records were reviewed and 108 horses with


strangles (cases) and 215 horses without strangles (controls) were identified. Cases were defined as horses with clinical signs of strangles (pyrexia, retropharyngeal lymphadenopathy, and mucopurulent nasal discharge) that were associated with aconfirmed strangles outbreak or had positive results for S. equi on PCR assay or bacteriological culture. Controls were defined as horses with pyrexia that did not meet the other criteria for cases. Data including signalment, clinical signs, diagnostic test results, and disease complications and outcome were compared between cases and controls. Variables were identified using logistic regression.


Clinical signs of strangles were not evident in 12 of 25


cases classified as S. equi carriers (infected >40 days). Predictor variables associated with strangles included mucopurulent nasal discharge and external abscesses in the pharyngeal region. Strangles was more likely to be diagnosed in the spring than in the summer. Cases with anaemia were more likely to develop purpura haemorrhagica than were cases without anaemia. No risk factors were identified for the development of guttural pouch empyema or metastatic abscesses. These results indicated that not all horses infected with S. equi develop clinical signs of strangles. Guttural pouch endoscopy and lavage with PCR assay of lavage fluid samples is recommended to identify S. equi carrier horses.


Radial fracture risk factors


The aim of this study by Suzanne Stewart and colleagues at the University of Pennsylvania, USA, was to determine survival to discharge of horses with radial fractures and also to determine risk factors affecting survival to hospital discharge in conservative and surgically managed fractures. Medical records and radiographs of horses admitted with


radial fracture were reviewed and horses with osteochondral fragmentation of the distal aspect of the radius or stress fractures were excluded. Evaluated risk factors were age, fracture configuration, surgical repair method, surgical duration, hospitalisation time, implant failure rate, and surgical site infection (SSI) rate. Of the 54 horses that met the inclusion criteria, overall


survival to discharge was 50%. Thirteen (24%) were subjected to euthanasia on admission because of either fracture severity, presence of an open fracture or financial constraints. Fourteen (26%) horses with minimally displaced incomplete fractures were conservatively managed and 12 (86%) survived to discharge. Twenty-seven (50%) horses had surgical treatment by open reduction and internal fixation (ORIF) and 15 (56%) survived to hospital discharge. Open fractures were significantly more likely to develop SSI, which also resulted in a 17-fold increase in implant failure. Of 8 surgically managed horses with an open fracture, 6 did not survive to discharge. Outcome was also adversely affected by age and surgical duration >168 min. Presence of SSI trended towards a decreased survival rate. Prognosis for survival to discharge with minimally


displaced incomplete fractures is good. Young horses have a good prognosis survival to discharge for ORIF, whereas ORIF in adult horses has a poor prognosis and SSI strongly correlates with catastrophic implant failure.


Gentamicin concentrations in hospitalised horses


The objectives of this retrospective study by J.R. Bauquier and colleagues in the USA and Australia were to determine the relationship between gentamicin dose and plasma concentration in hospitalised horses, and to identify a starting dose range to achieve peaks >32 lg/ml. Gentamicin is an aminoglycoside antimicrobial commonly


used in horses at 6.6 mg/kg i.v. once daily. Therapeutic drug monitoring (TDM) can confirm desired peak concentration is


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