At least 21 horses have died after coming down with a mysterious ailment moments before they were scheduled to compete in the prestigious U.S. Open polo tournament.
Though the Florida Department of Agriculture was conducting lab tests to determine the cause of death, veterinarians said they suspected the horses were probably killed by some sort of poison.
At least 14 of the horses from Venezuela's Lechuza Caracas team, worth an average of $100,000 each, died Sunday after several of the animals became dizzy and collapsed as they were being unloaded at the International Polo Club Palm Beach.
Seven horses died at the club; a total of 15 from the Venezuetan team died yesterday. The rest died overnight or early this morning as they were receiving medical care or en route to medical treatment, said Terence McElroy, a spokesman for the state's Department of Agriculture.
The results of lab tests to determine the cause of death could take up to a week, McElroy said.
Dr. Scott Swerdlin, one of the veterinarians who treated the horses, said they died after they developed pulmonary edema, a buildup of fluid in the lungs, which sent them into shock.
"I've never seen anything like this," Swerdlin said. "Not only is it frustrating, it's tragic. We're emotionally drained too. It was just horrible."
Swerdlin said it was likely that an unidentified toxin in the animals' feed, vitamins or supplements could have killed them.
Dr. Rob Boswell, another veterinarian at the Palm Beach Equine Clinic near the polo club, who did not treat the horses, also said "a toxic substance would be very high on your list" of possible causes of death.
"It's probably some sort of a toxin, a chemical, something that got into their system," he said. "It could be a food additive, something in the hay, it's hard to say at this time."
"I haven't seen anything like this in 25 years of practice."
A team veterinarian who was at the scene said tests will need to determine the trigger for what he believed was heart failure among the horses. The horses died "almost certainly of an intoxication of some sort that they consumed," Dr. James Belden told the Palm Beach Daily News.
Belden said it remains to be seen "whether it's something in the environment or something that the horses were exposed to," but added it was unlikely that the horses were given steroids or tainted medication.
Boswell also said that though competitive polo is less regulated than horse racing, he thought it was unlikely that the horses were given dangerous performance-enhancing drugs.
"There probably are things that are given to horses to enhance their performance. I'm just not aware of any in this situation," he said.
Two of the horses collapsed as soon as they were unloaded on the way to the field, said Tim O'Connor, a spokesman for the Polo Club. Soon several others showed signs of dizziness and collapsed. Veterinarians who were at the event tried to treat the horses, cooling them with fans and water, he said.
"Horses can collapse or have heart attacks but nothing like this has ever happened," O'Connor said.
The U.S. Polo Association, the sport's governing body, is reportedly expected to open an investigation. The association's president did not immediately return a call for comment.
McElroy said he could neither confirm nor deny whether a criminal investigation was underway. The Palm Beach County Sheriff's Office said it was not investigating the incident.