It is not usual to see a horse collapse during or soon after an athletic event, but it does happen. A study evaluated the frequency of this occurrence, which can provide sound advice for clients engaged in equestrian activities [de Solis, C.; Althaus, N.; Basieux, F.; Burger, D. Sudden death in sport and riding horses during and immediately after exercise: A case series. Equine Vet J, 2018].
Of 57 cases, event horses topped the statistics with 40.4% sudden deaths. The most common breed was the Thoroughbred. Collapse in these cases occurred during exercise in nearly 72% of the time and soon after exercise in another 28%.
Death occurred during or near the time of competition in 42% with the other 58% dying during or near the time of a pleasure or training ride. Because sudden death is known to occur after exercise stops and/or not always during competitive events, it is likely that the incidence of equine sudden death are underestimated due to lack of reporting.
About one-third of the 57 cases were strongly suspected or diagnosed on post-mortem as having a fatal cardiovascular event. Nearly 23% of riders on these horses were injured, particularly in their extremities.