Recently Catriona Lyle led a multicentre study in an attempt to gain a better understanding of the problem and find ways to reduce the risk of sudden death occurring. The work, funded by a Horserace Betting Levy Board scholarship, was undertaken at the Royal (Dick) School of Veterinary Studies in Edinburgh.
Lyle coordinated the study drawing information from racecourses in North America, Australia, Japan and Hong Kong. Post-mortem data from 284 cases over 20 years were studied. In the UK post-mortem examinations are not always carried out in cases of sudden death and so gaining access to these international records was essential.
She explains:“The study has shown that the cause of death can be quite variable, ranging from severe lung bleeding to a pelvic fracture that causes massive bleeding into the abdomen. But in approximately half the cases I studied, the pathologist was uncertain as to the cause of death. The most likely explanation for death in these situations is cardiac rhythm irregularities, but this is very difficult to prove.”
Following her analysis of these international data, Lyle then looked at cases of sudden death in British racehorses. She found that sudden death of horses during races is a very rare event. Over a seven year period, in 705,914 race starts, there were 201 sudden deaths on British racecourses. The same syndrome is known to occur in eventing, show jumping and hunting but statistics have not been established in these sports.
In the UK study, she found that increasing age is a risk factor, steeplechases posed more of a risk than flat races and racing during the summer was associated with a greater risk of sudden death. However, this should be put in the context that, on average, steeplechasers are older than hurdlers or Flat horses. Horses that had raced within the last 60 days were less likely to be affected.
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