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VET FORUM: THE EXPERT VIEW By ROB PILSWORTH, MA VETMB BSc CertVR MRCVS
Death in the afternoon The cause and prevention of sudden collapse of racehorses on the racecourse
Why do apparently fit athletes collapse and die? It seems inconceivable that ‘super-fit’ elite athletes should be susceptible to sudden death during competition, either in the human field or in horseracing but sadly this is just the case. In 2013, Fabrice Muamba famously collapsed and technically ‘died’ during a Premier League football match at Tottenham’s White Hart Lane ground. Rapid attention by paramedics and the medical team in attendance allowed him eventually to make a full recovery. In the same year, an Italian footballer Piermario Morosini, who was only 25, collapsed during an Italian football match and died. Both of these players suffered heart attacks, despite being supremely fit, lean and young. So do all of our unexpected equine fatalities fit into the same category? To answer this, Lyle and her team collated data from six racing jurisdictions around the world. These included horses from California and Pennsylvania in the USA, Victoria and Sydney in Australia, Hong Kong and Japan. Because unexpected death in the racehorse is a
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rare event, it was necessary to collate data from so many training centres in order to get statistically reliable information. Pulling together data from so many different sources allowed the team to examine a total of 268 fatalities and find out why they died.
Cause of death The first interesting finding was that the definitive diagnosis of the cause of death was only made in just over half of the cases. A presumptive cause of death was established in a further 25% but this left nearly a quarter of the horses investigated lacking any evidence at all to explain why they died. The most frequent reason for fatal collapse was failure of the heart, or lungs, or both and these comprised over half of the definitively diagnosed cases. Of these cases of heart/lung failure, the majority involved massive pulmonary haemorrhage (bleeding into the lungs) and only a fifth to primary heart failure. Interestingly, in the horses that died of acute lung ‘bleeds’, when the lung tissues themselves were examined in depth under the microscope, the type of cell which indicates an on-going history of ‘bleeding’, the haemosiderophage, was rarely encountered. This seems to indicate that when lung bleeding occurs to the degree of severity to cause death, it is probably for different reasons than the low-grade lung bleeding commonly encountered in training and racing. The horses that died of pulmonary haemorrhage in this study do not appear to have been long-standing ‘bleeders’.
Blood loss which we can’t see The second biggest group of horses with a definitive cause of death comprised cases of haemorrhagic shock. These made up just over a quarter of the positively identified cases. This haemorrhagic shock usually occurred as a result of profuse bleeding, either from a blood vessel which had spontaneously ruptured, or from laceration to large blood vessels in the hind legs by the sharp edges created in a displaced fracture of the pelvis, a relatively common athletic injury. Unfortunately, because the bleeding takes place internally, these horses give no clue to the existence of a serious problem until the blood pressure drops below a minimum threshold at which point the horse collapses. By then any chance of saving the horse’s life with transfusion or intravenous fluid therapy is unfortunately long-gone. In nearly half of the cases subjected to post-mortem in which there was a large amount of blood free in the abdomen, the exact site of the ruptured blood vessel was never found. Interestingly, rupture of the aorta, the massive vessel leading from the heart, (the socalled ‘ruptured aortic aneurysm’) which is often anecdotally suspected to be the cause of sudden death during or immediately after racing, was only found in two horses in the whole study. Just over a tenth of the cases with a defined cause of mortality were attributed to trauma to the central nervous system. These included cases of spontaneous fracture of the vertebrae that resulted in spinal cord trauma or skull fracture with associated brain trauma. While
GEORGE SELWYN
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he loss of a racehorse through injury or death is always a bitter blow. Thankfully, unexpected death during competition is a rare event, but it does happen regularly enough to be of concern to those involved in the industry, and importantly impacts on the public’s perception of racehorse welfare. Events like the collapse and death of the 11-year-old Battlefront in the Foxhunter Chase at last year’s Grand National meeting lives on in the mind of the viewing public, despite the fact that 95 other horses racing on the same day finished in one piece. Fatalities like this have a disproportionate impact on the public’s perception of racing so how common are they, what causes them, and is there anything we can do about them? These questions have recently been addressed by a large research effort, funded by the Horserace Betting Levy Board, and involving workers from the Royal (Dick) School of Veterinary Studies in Edinburgh, the Animal Health Trust in Newmarket, the School of Veterinary Medicine of the University of Glasgow, with collaboration from the British Horseracing Authority. Catriona Lyle has been the lead research worker coordinating studies both in the UK and internationally on the causes and frequency of unexpected sudden death in the equine athlete.
The great Persian Punch collapsed during the running of the Sagaro Stakes at Ascot
THOROUGHBRED OWNER & BREEDER INC PACEMAKER