Key result
Sudden racehorse death linked to severe myocarditis possibly secondary to an infected castration wound.
Why the study?
Exercise-associated sudden death is a major racing industry concern, and cases presumed to be cardiac often yield unrewarding necropsies without microscopic lesions.
Case Report (n=1)
No
This case report highlights the utility of a standardized cardiac examination protocol in identifying severe microscopic cardiac lesions in racehorses with exercise-associated sudden death that appear grossly normal.
May link infected castration wounds to fatal equine myocarditis; leaves open whether wound protocols or cardiac screening reduce sudden death risk.
Exercise-associated sudden death (EASD), defined as acute collapse and death in an apparently healthy racehorse during or within ~1 h after exercise, is currently among the top concerns in the racing industry. Cases of EASD with no cause of death identified at necropsy are frequently presumed to be of cardiac origin. In such cases, in addition to a regular necropsy, a cardiac examination protocol is performed that includes a detailed gross examination and microscopic evaluation of 11 regions of the heart. Very often this protocol is unrewarding because there are no microscopic lesions to explain the presumed cardiac event. Here we describe the necropsy of a 3-year-old, Thoroughbred gelding that collapsed a few minutes after a workout. The heart was grossly unremarkable, but significant histologic lesions that included multifocal to diffuse cardiomyocyte degeneration and necrosis, lymphoplasmacytic myocarditis, and myocardial fibroplasia were found, particularly in the right and left ventricular free walls and in the interventricular septum. Other lesions included severe pulmonary edema and congestion, splenic congestion, an open castration wound with localized suppurative inflammation and bacteria in the scrotum, and lymphoplasmacytic interstitial nephritis. We believe that the cardiac lesions were severe and extensive enough to have contributed to death. A cause for such lesions was not definitively identified, but it is possible that the infected castration wound predisposed to myocarditis. This case serves as an example of the use of the cardiac examination protocol to map and evaluate lesions in EASD cases.
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Acevedo et al. (2026) conducted a case report in Exercise-associated sudden death (n=1). Infected castration wound was evaluated on Cardiac lesions and cause of death. A 3-year-old Thoroughbred racehorse that died suddenly after a workout exhibited severe cardiac lesions, including myocarditis and myocardial fibroplasia, possibly secondary to an infected castration wound.
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