SummaryReasons for performing study: To improve the understanding of exercise related sudden death in Thoroughbred racehorses.

SummaryReasons for performing study: Sudden death adversely affects racehorse welfare, jockey safety and the public perception of horseracing. Objective: To describe the risk of racing-associated sudden death in Thoroughbred racehorses in the UK from 2000 to 2007, to identify whether there were risk factors uniquely associated with sudden death and to improve the understanding of the pathogenesis of racing-associated sudden death by identification of risk factors for such cases. Methods: A sudden death was defined as an acute collapse and death, in an apparently healthy Thoroughbred racehorse, during or immediately after racing, in the absence of clinical data indicative of a catastrophic orthopaedic injury. The retrospective study included 201 case race starts and 705,712 control race starts. Univariable and multivariable logistic regression were used to identify risk factors for sudden death at any one start. Results: In the multivariable model, age, distance, race type, season and number of starts in the 60 days prior to the race were associated with sudden death. Conclusions:The risk factors identified in this study are not uniquely associated with sudden death and have been also been identified in studies using all causes of fatality as the outcome. These data suggest that a generic approach to reduce fatal musculoskeletal injury and sudden death may be possible. Potential relevance: The identification of risk factors allows speculation on the underlying mechanisms of sudden death in racing. This may stimulate hypothesis-led investigations into the pathogenesis of exercise-related arrhythmias, exercise-induced pulmonary haemorrhage and blood vessel rupture.

Background: Episodic collapse in horses has equine welfare and human safety implications. There are, however, no published case series describing this syndrome. Objectives: To characterize the cause and outcomes for horses referred for investigation of episodic collapse. Animals: Twenty‐five horses referred for investigation of single or multiple episodes of collapse. Methods: Retrospective study. Clinical records from the Dick Vet Equine Hospital, University of Edinburgh from November 1995 to July 2009 were searched using the following keywords: collapse, collapsing, fall, syncope. Collapse was defined as an incident in which the horse lost postural tone with or without progression to recumbency and with or without loss of consciousness. Long‐term follow‐up information was obtained by telephone conversation with the owner. Results: A final diagnosis was reached in 11 cases, namely cardiac arrhythmia (4), right‐sided heart failure (1), hypoglycemia (2), generalized seizures (2), and sleep disorder (2). A presumptive diagnosis was reached in 8 cases, namely neurocardiogenic syncope (5), exercise‐induced pulmonary hemorrhage (2), and generalized seizures (1). No diagnosis was reached in 6 cases despite comprehensive investigations. Three horses were euthanized at presentation. Treatment was attempted in 9 horses with 6 cases having successful outcome before discharge. Follow‐up information was available for 14 of 19 horses discharged from the hospital. Only 1 of these horses was observed to collapse after discharge. Conclusions and Clinical Importance: Definitive diagnosis was more likely to be reached in cases with multiple episodes of collapse. Horses in which 1 episode of collapse occurred did not necessarily collapse again.

EQUINE grass sickness (dysautonomia) is a neurological disease associated primarily with degeneration of neurons in the autonomic nervous system (including the enteric nervous system), although involvement of the somatic nervous system has also been widely reported. It affects all Equidae, is usually fatal and has an approximate incidence of 1 per cent in some parts of the UK. This article discusses the clinical aspects of the disease and summarises the findings of recent research into the aetiology and epidemiology of the condition.