The young man's name was Hank Gathers, and he was 23 years of age. He was a basketball star at Loyola Marymount University in California. The year was 1990, and Gathers the year before had become only the second player in Division 1 history to lead the nation in both scoring and rebounding in the same season. He was on his way to another landmark season. It was West Coast Conference tournament time in the early stages of March Madness on March 4 and Loyola Marymount was playing Portland. Suddenly, during the game, Gathers collapsed, went into convulsions, and died. He was a victim of a rather mysterious sudden death syndrome that periodically strikes both human and equine athletes.

In most cases, no one has seen it coming. The athlete has been fit and healthy in all outward appearances and tests. In the Gathers case, there had been at least one warning. He had fainted at the free throw line the previous December. He was diagnosed with cardiac arrythmia, an abnormality of the heart rate, and he was placed on medication. He was held out of action for two games, then was allowed to return. He complained that the medication was making him sluggish, so it was reduced. It would later be learned that he also suffered from hypertrophic cardiomyopathy, a thickening of the heart muscle.

The death of Gathers created a controversy. Should he have been allowed to compete after suffering the fainting spell during a game? Should his medication have been reduced? As is often the case, there were more questions than answers.

The major question that surfaces in the wake of such an incident concerns the ability to detect or predict that sudden death might occur when certain conditions are combined with athletic exertion. In many cases, especially when horses are involved, it is impossible to predict.

Sometimes the death of a horse in competition isn't all that sudden, such as in the case of death during endurance competition where fatigue and terrain become factors. There were, for example, two horses that died during the 100-mile endurance race that was held as part of the World Equestrian Games in Spain in 2002. Later in this article we'll discuss what happened.

But there is more to the story than that. Sometimes horses die suddenly when they aren't involved in athletic competition. You walk out to stall or paddock one morning and your good trail horse or companion animal is lying dead, even though it had appeared normal and healthy when you fed the night before. Sometimes there is an easily recognized reason for the death; with others the reason remains a mystery.

Sudden Death in Athletes

The good news is that sudden deaths are rare, although they do occur in racing and other strenuous competitions, such as eventing and jumping. Most deaths on the racetrack are because of catastrophic musculoskeletal injuries that result in the horse being euthanatized, but some occur when a horse simply drops dead during a race or a training session.

Some of the sudden deaths in racehorses are never truly diagnosed. Others are apparent at necropsy, says Rick Arthur, DVM, former president of the American Association of Equine Practitioners (AAEP) and a racetrack veterinarian in California. "Most appear to be cardiac problems, either endocarditis (involving the membranes lining the cavities of the heart and the connective tissue bed on which it lies) or myocarditis (involving the muscular tissue of the heart)," he says.

There also have been instances of sudden death, Arthur says, as the result of major vessel ruptures. These ruptures would normally occur in the aorta or pulmonary artery.

"My impression is that those are less common today," Arthur says. "That is probably because of better deworming programs. Strongyles were thought to be a major cause as they migrated through arterial blood vessels, causing damage and vessel weakness. This is the same reason that colic is less common today at the racetrack."

The sudden death syndrome is not a new one and has been studied for some time, but the studies have produced as many questions as answers. Through the years, the syndrome has continued to baffle researchers, with some of the deaths never being explained in a satisfactory manner.

In one bit of research, the case records and necropsy reports were reviewed for 25 Thoroughbreds that died suddenly at three Chicago racetracks. The findings were published in the Journal of the American Veterinary Medical Association in 1985. The researchers found that 21 of the 25 horses died while either racing or on the training track. Sixteen were females and nine were males. The researchers found that only eight of the 25 horses had lesions sufficient to account for the cause of death. In six of those eight cases, death was caused by massive thoracic or abdominal hemorrhage. One of the horses died of severe pre-existing pulmonary (lung) disease, and another died of encephalitis and cardiac papillary muscle fibrosis.

That left 17 of the deaths unexplained. The researchers postulated that these unexplained deaths were a result of exercise-induced acute cardiovascular failure.

As already indicated, exercise-induced pulmonary hemorrhage (bleeding) is implicated in some of the sudden deaths. This was borne out by a study that is still under way in Australia. In 2001, Racing Victoria in Australia set up a mandatory post-mortem program for every horse that died while racing or training on metropolitan tracks. The post-mortem examinations are performed at the Veterinary Clinical Centre of the University of Melbourne. The program is under the direction of Lisa Boden, PhD, of the University of Melbourne.

In the first three-plus years the program was in place, 77 horses were examined. Sixty-one of them were from metropolitan tracks and 16 were from county or provincial racecourses. Of the 61 horses from metropolitan tracks, 46 were euthanatized for musculoskeletal injuries. The most common injury was fracture of a forelimb cannon bone. However, 15 of the horses died of other causes, with sudden death figuring into a number of them.

The most common causes of sudden deaths on racetracks, Boden reports, were exercise-induced pulmonary hemorrhage (bleeding into the lungs) and left-sided heart failure.

Boden's research will continue through this year (2005) with a prime goal being to identify key risk factors associated with severe injury and death so that effective preventive measures can be implemented.

Gary Norwood, DVM, a track veterinarian in Louisiana and a former AAEP president, says he has had experience with the sudden death syndrome on the track, but that fortunately, it has been rare.

When deaths have occurred, he says, they primarily have been the result of either a heart problem or severe hemorrhaging in the lungs. In some cases, he says, it has been impossible to pinpoint the cause of the heart problem. The horse dropped dead during exertion, but no one could be certain why, even when a complete necropsy was performed.

When death is caused by massive hemorrhaging in the lungs, Norwood says, blood vessels simply burst during exertion and the horse quickly bleeds to death.

A more rare bleeding occurrence can involve the artery in the guttural pouch, he says. There have been instances where fungus has weakened the artery and caused bleeding that resulted in death.

The sudden death syndrome also has raised its head in three-day eventing and jumping competitions. Joseph O'Dea, DVM, who served as the U.S. Olympic team's veterinarian for 20 years and was involved in international competition even longer, says that most sudden deaths in competition that did not result from injury suffered in a fall (such as a broken neck) involved a ruptured aorta or stroke. (O'Dea also served as the 1970 president of the AAEP and authored the book Olympic Vet).

It has been virtually impossible to predict something as lethal as a ruptured aorta in a competing horse, he says. Perhaps, however, modern technology will arrive at that point one day. O'Dea is living proof that detection of a problem area on the aorta can save a life. He was diagnosed with having a weak spot on his aorta that had the potential of rupturing. At age 77, O'Dea agreed to surgery that involved inserting a "nylon sleeve" into the aorta to shore up the weak area. That was seven years ago, and O'Dea is still alive and active.

Catherine Kohn, VMD, of The Ohio State University, also has had experience--both firsthand and via accounts of colleagues--with the sudden death syndrome in three-day eventing. She is quick to say that there have been very few cases. Kohn serves as an adviser to the U.S. Equestrian Three-Day Event team and has worked as a veterinarian at many Olympic-level three-day events through the years.

In the cases of sudden deaths during events that have come to her attention, Kohn says it would have been virtually impossible to detect the condition or predict that sudden death would occur in any of the individuals.

One horse, for example, died as the result of an aneurysm in the abdomen and bled to death. Another, she says, also bled to death as the result of a hematoma on the pancreas. Still another event horse died as the result of hemorrhaging that involved the lungs.

In eventing, Kohn says, a strong effort is made to detect any problems that might affect the horse in advance of the competition as well as while the competition is occurring. To that end, each horse is given a thorough examination prior to the event and is examined again during the competition to determine its fitness in the wake of phases that could cause physical problems to develop.

All of the information learned about the horse during the examinations by the veterinary team, she says, is recorded and follows the horse through the competition.

In intense competitions like three-day eventing, Kohn says, the horse is performing at the extreme upper end of its capability and the potential for musculoskeletal injury--and even sudden death--is present despite the best efforts to detect and resolve problems in advance.

Long-Term Competition Deaths

We turn now to equine deaths that aren't all that sudden, but that result in part from the competition with which the horse is involved. The deaths of two horses in the 100-mile endurance race at the World Equestrian Games (WEG) in 2002, necropsies revealed, resulted from metabolic failure associated with fatigue.

One of the horses was a 9-year-old gelding named Floyd that was ridden by Malaysian competitor Nik Isahak Wan Abdullah; Floyd died during the race. The other horse, also a 9-year-old gelding, was named Sir Fire and ridden by Anna Maxenchs Serra of Spain. Sir Fire collapsed and died after the race.

The rules for the WEG endurance event stipulated that the competitors had to maintain a minimum speed as they covered the 100-mile course, which traversed rolling farmland. Along the route, the contestants were required to stop at four checkpoints for a pre-determined period of time so that the horse's pulse, respiration rates, and overall fitness could be evaluated. Normally, the horses would have been required to travel at the rate of eight miles per hour over the course, but because there had been a rainstorm the night before, turning the course into a quagmire, the required speed was reduced to six miles per hour. In addition, the rest time at the first two checkpoints was increased from 30 to 40 minutes. Of the 140 horses that started the race, 64 finished.

The judicial committee of the Federation Equestre Internationale (FEI) conducted an in-depth study into the two deaths. It reported its findings in April of 2003, declaring that the cause of death in each case was associated with fatigue and exhaustion. There were no sanctions against any individual or organization.

However, the committee did recommend that current rules and veterinary procedures should be reviewed.

Pleasure Horse Deaths

We have discussed the sudden deaths of horses involved in strenuous athletic competition, but what about the companion animal or trail riding mount that is found dead in stall or paddock? We turn to Jill Johnson, DVM, of Louisiana State University, who has given a number of presentations on the subject, in an effort to prepare veterinarians and horse owners to be good sleuths in helping to deduce what caused the death.

"Sudden death," says Johnson, "is defined as sudden and unexpected death in an apparently healthy horse occurring within 12 hours, often between periods of observation, such as overnight."

In some cases, the cause of death is obvious, such as the horse being electrocuted by an exposed high-voltage electrical wire, and in others it remains a mystery, even after necropsy.

Johnson's goal is to guide horse owners and veterinarians in being good detectives so that the cause of death can be determined and can be eliminated for other horses on the premises.

While a part of her presentation is geared toward veterinarians, concerning the types of samples to be taken for later examination, a portion of what she says also applies to owners. Here, in summary form, is what she suggests as a beginning investigative approach--one that also could apply to owners who would pass the information on to the examining veterinarian in the wake of a horse's sudden death:

  • Determine when the horse was last observed alive, thus setting the outside limit for the time of death.
  • Be aware of the horse's previous medical history. Previous episodes of fainting, for example, might suggest hyperkalemic periodic paralysis, organic neurologic lesions, or intermittent cardiac arrhythmias. Late pregnancy or early postpartum mares might be at risk for such things as hypocalcemia (lack of calcium), uterine torsion, or uterine vessel rupture.
  • Determine whether the horse had received medication that might have caused a lethal reaction or perhaps was improperly administered.
  • Determine whether the horse had been involved in recent physical activity, such as racing or breeding, that could have resulted in trauma.
  • Determine whether there was potential for malicious mischief on the part of someone who had access to the horse.
  • Examine the environment where death occurred for evidence of environmental hazards, such as toxic agents, poisonous plants, exposed electrical wiring, empty chemical containers, electrical appliances such as water heaters and lights, plastic bags, syringes, and needles.
  • Determine what the horse had been eating.
  • Examine the source of water, especially groundwater.

Take-Home Message

The sudden death of a horse is a traumatic event, whether on the field of competition or in the home paddock or pasture. While there are answers for some sudden deaths, others remain a mystery and demand continuing research. If your horse dies suddenly, investigate thoroughly; it might prevent other horses from being lost.

CALIFORNIA STUDY: UC Davis Researches Racehorse Deaths

A study launched by the California Horse Racing Board (CHRB) in 1991 and carried out by pathologists on the staff of the University of California, Davis, has resulted in some interesting statistics and information concerning the sudden death syndrome. The study involves performing a necropsy on every horse that dies on a California racetrack or training track where the racing board has jurisdiction. One of the prime goals of the study is to determine how and why a horse suffers a catastrophic injury while racing or training. The ultimate goal, of course, is to determine ways to prevent those injuries.

However, catastrophic injury is not all that is being studied. Researchers are trying to get a handle on other causes of death, such as the sudden death syndrome.

Alex Ardans, DVM, is director of the California Animal Health and Food Safety Laboratory Systems, which is a part of UC Davis and whose five laboratories are responsible for the necropsy work. He says since the study began in 1991, there have been 3,463 equine deaths during racing and on training tracks under the jurisdiction of the CHRB. The majority of the deaths, he says, have resulted from catastrophic injury, but 215 of them have been attributed to sudden death syndrome.

Of the 215, Ardans says about 20% have been the result of pulmonary hemorrhage--severe bleeding in the lungs that occurred during or in the immediate wake of strenuous exercise, such as a race.

A portion of the sudden deaths have been attributed to cardiovascular problems. Ironically, Ardans says, one horse necropsied shortly after the death of Hank Gathers was suffering from the same malady that was blamed for that stellar athlete's death. There was thickening of the heart muscle, he says, but a portion of the heart also was distended and flabby, as was the case with Gathers.

Some of the sudden deaths, Ardans says, have been the result of arteriosclerosis--hardening of the arteries. In some of the horses necropsied, the disease was so advanced that very little blood was getting through and it was a mystery how the horses could function, much less race.

Other sudden deaths might have been related to influenza. There have been cases, Ardans says, where inflammatory lesions in the heart caused death. It is suspected, he says, that the lesions were the result of inflammation brought on by influenza. The influenza virus is a potent one, and there is much to be learned about the devastating effects it can have on human and equine bodies.

A few of the sudden deaths in California, Ardans says, have been attributed to toxicosis, resulting when the horse ingested a toxic substance in its feed.

In some cases, determining the cause of sudden death takes extensive sleuthing. Ardans recounts one incident where a horse dropped dead on the track and didn't move. There was nothing in the heart and lungs that would indicate cause of death. However, it was discovered that the horse had fractured a sesamoid and when it flipped over as a result of the injury, he landed in such a way that he fractured his neck, severing the spinal cord.

There is much to learn about sudden death syndrome, but the accumulation of data at places like UC, Davis, are steadily--albeit slowly--making progress in solving at least some of the mysteries.

"The more we look, the more we are going to find," Ardans says.--Les Sellnow

About the Author

Les Sellnow

Les Sellnow is a free-lance writer based near Riverton, Wyo. He specializes in articles on equine research, and operates a ranch where he raises horses and livestock. He has authored several fiction and non-fiction books, including Understanding Equine Lameness and Understanding The Young Horse, published by Eclipse Press and available at or by calling 800/582-5604.

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