University of Florida Vet Faculty Work to Solve Polo Pony Mystery

Postmortem testing conducted by University of Florida College of Veterinary Medicine pathologists and toxicologists on a group of prized polo horses that collapsed and died April 19 in Wellington, Fla., drew international attention, with riveted members of the public and the press wanting answers about the mysterious cause of death.

Blood and tissue samples were gathered from 15 horses on which UF pathologists conducted necropsies. Six other horses had been sent to the Florida Department of Agriculture and Consumer Services' diagnostic laboratory in Kissimmee, Fla., for postmortem examinations. The necropsies of all 21 horses yielded no answers, nor did subsequent microscopic examinations. Even the UF Racing Laboratory, which routinely conducts toxicology screening tests of racehorses in the state, revealed nothing initially that could explain the horses' sudden deaths.

Subsequent tests conducted by UF toxicologist David Barber, however, verified the presence of life-threatening concentrations of selenium in the horses' blood and liver samples. The concentrations were found to be 10 to 15 times higher than normal in the blood and 15 to 20 times higher than normal in the liver.

"Our role in testing was key, not only because we were able to verify the toxic levels of selenium found to be present in the blood and liver of these horses, but also because through additional testing conducted at our Racing Lab, we were able to rule out the presence of common performance-enhancing drugs," said Dr. John Harvey, the college's executive associate dean and a board-certified clinical pathologist.

"This is significant, because in ruling out other drugs that could have killed these horses, we essentially were able to corroborate the assessment that indeed these deaths were likely caused by an accidental overdose rather than due to malicious or criminal intent."

UF received 15 horses for necropsies around 3 a.m. Monday, April 20. The first group of six horses had been taken to the state diagnostic laboratory in Kissimmee, filling it to capacity.

An eight-person UF pathology team led by Dr. Lisa Farina and Dr. Jeff Abbott, both board-certified anatomic pathologists, immediately set to work conducting the necropsies of eight of the 15 horses. The task was completed at approximately 5 p.m. Monday. Soon after, a request came to necropsy the remaining seven horses. All of the necropsies, including those performed at UF and those conducted at the state's diagnostic lab, were complete by day's end on Tuesday.

Wednesday morning, Farina and her colleague, Dr. Michael Dark, an assistant professor of anatomic pathology, began examining slides with tissue samples under the microscope while a CNN reporter videotaped them at work.

By this time, reports had surfaced that individuals associated with the polo team had admitted giving vitamin supplement shots to the horses shortly before they died. Speculation intensified as to what exactly had been administered and whether any of the ingredients in the supplement injections could have caused the horses' deaths.

Meanwhile, blood samples taken from some horses before they died had arrived at UF and were being tested at the UF Racing Lab, under the direction of Dr. Richard Sams. Pathologists and toxicologists remained puzzled, as nothing conclusive had yet emerged.

On Thursday, April 22, the focus of the story took a dramatic shift when a spokesperson for a private pharmacy said that the horses had received an incorrect dose of one of the ingredients used in a vitamin compound with which the horses had been injected (read statement). Because of ongoing law-enforcement and other investigations, the pharmacy did not initially release the name of the specific ingredient.

On the basis of this information, Dr. David Barber, an associate professor in the Center for Environmental and Human Toxicology in the college's department of physiological sciences, worked until late Thursday night conducting analysis of inorganic components of the vitamin supplement.

Testing was performed on samples from affected and an unaffected horse. Barber was not informed which horse was the "control" horse, he guessed the obvious after completing the testing. The unaffected horse was the only horse among those tested that showed normal levels of selenium in its blood, compared with very elevated levels detected in the blood of other horses tested. A pharmacy spokesperson later confirmed that selenium was incorrectly dosed.

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