Sudden Death in Sport Horses

Sudden death in sport horses is a rare, but traumatizing, tragedy. While it often gets significant media attention, particularly when it happens during high-level and/or international events, there’s been very little scientific study into these occurrences.

That’s why researchers in the U.S. and Switzerland recently teamed up with the Swiss Equestrian Federation to look into the statistics of sudden death in sport horses. Their overview of incident details, they said, is a good starting point for further research into the phenomenon in hopes of reducing the number of incidents.

“Sudden death is important because it affects not only the health of horses but also the safety of riders and the public perception of welfare during equestrian sports,” said Cristobal Navas de Solis, MS, PhD, LV, Dipl. ACVIM, of the University of Bern Vetsuisse Faculty, in Switzerland, and Texas A&M University College of Veterinary Medicine and Biomedical Sciences, in College Station, Texas.

In their study, Navas de Solis and fellow researchers, including Dominik Burger, DVM, also of the University of Bern, investigated the details of more than 50 sudden death cases in nine countries in North America and Europe. They specifically focused on sudden death in sport horses, excluding racehorses. They also did not include deaths related to musculoskeletal injuries (fractures, trauma, rotational falls, etc.). The horses had to have died during exercise or within an hour post-exercise to be included in the study.

The team gathered information through owner- and veterinarian-completed surveys. The researchers recruited these respondents through requests distributed by some national federations and select equestrian magazines, including on TheHorse.com. They received well over 100 reports but only investigated the cases that could provide enough relevant information for their study, they said.

Study Results

Thoroughbreds made up 40% of the cases the researchers investigated. Warmbloods made up another 20%. Quarter Horses and Paints represented 10% of the cases.

Twenty-three (40%) of the study horses were eventers. While many of those horses died during or within an hour of a competition’s cross-country phase, more than half died during or just after a training session outside of competition.

The remaining 34 horses included:

  • Nine leisure horses;
  • Eight show jumpers;
  • Five dressage mounts;
  • Four fox hunters;
  • Four polo ponies;
  • Three Western performance horses (cutters, ropers, and team penners); and
  • One endurance horse.

Deaths occurred at all levels, although they were more frequent in horses competing or training at more advanced levels. Respondents considered 24 horses “advanced,” 13 “intermediate,” and 15 “beginners.” Five horses’ experience level was unknown or not applicable.

The fact that there were more cases of advanced-level horses is particularly concerning since, generally, fewer horses compete at an advanced level compared to other levels, the researchers said. However, Navas de Solis stressed that it’s important to remember that any horse can die suddenly during or just after athletic activity.

“Some causes of sudden death are more common in high-level horses,” he said. “But sudden death definitely happens in pleasure riding horses, just as it does in humans who practice sports as a hobby.”

A third of the horses had previous medical problems, but few had issues such as heart conditions that would stand out as being risk factors for sudden death, the researchers said. And most of the horses showed no signs of problems before the sudden incident, except perhaps slowing down or disorientation in a few cases.
More than 70% of the horses died during exercise, the others collapsing within an hour after. Only 40% of the horses died during or just after a competition. Most died during (or just after) training or pleasure riding.

“Sudden death is an ethical concern, like many other diseases, as it is our responsibility to take care of our equine partners,” Navas de Solis said. “But sudden death also concerns the safety of riders.”

In about a quarter of the cases, riders sustained injuries, including concussions, sprained ankles, broken ribs, and a fractured femur. No human deaths were reported.

Looking for Answers About Sudden Death

Despite public complaints inferring that horses suffering sudden death might be mistreated, Navas de Solis said he doesn’t have this impression at all.

“I believe that the majority of owners, riders, and trainers were heavily invested in the well-being of their animals, perhaps more than loud organizations that claim to defend animal rights,” he told The Horse. “The letters that we received from many riders describing their feelings after the loss of their equine friends would bring tears to your eyes.”

Research into the issue could lead to a better understanding of why it happens, as well as how to prevent it, he said. It’s possible that better horsemanship and education in sports medicine and training could reduce the risks, but first the scientists need to identify what’s lacking. Their research could be improved through more collaboration, he added, as they met with some resistance during this initial investigation.

“Thankfully, many equestrian and veterinary organizations like US Equestrian, the United States Eventing Association, the American College of Veterinary Internal Medicine, the American Association of Equine Practitioners, The Horse, the Swiss Equestrian Federation, Swiss Eventing Club, and many other journals and organizations that are cited in our article, were very keen to collaborate and I want to thank them,” he continued. “The only way that we are going to solve this problem is if riders, trainers, veterinarians, and equestrian organizations work together in the same direction.”

As research continues, so does the chance to find answers, said Navas de Solis.

“If we can give horse owners, trainers, and riders reliable tools to prevent sudden death,” he said, “most of them would use them in a heartbeat.”

The study, “Sudden death in sport and riding horses during and immediately after exercise: A case series,” was published in the Equine Veterinary Journal.