Piroplasmosis Update: 20 Positive, Tracing Exposed Horses

Florida agriculture officials announced Sept. 8 that 20 horses have been confirmed positive for the foreign animal disease equine piroplasmosis, but even though this might sound grim, the news isn't all bad.

All of the positive horses have thus far been directly linked to one another, indicating that free-roaming insects have not played a role in the spread of the disease. According to Mike Short, DVM, equine programs manager for Florida's Division of Animal Industry, it looks like the investigation is beginning to wrap up, with investigators completing traceback and testing horses exposed to positive horses.

The disease is believed to have spread via management practices that resulted in the transfer of whole blood between horses (for example, shared needles). No foreign ticks have been found among the 60 that investigators from Florida's Department of Agriculture and Consumer Services collected and tested from positive or surrounding premises, according to a statement released by the department. Additionally, none of the domestic ticks they've captured have tested positive for Babesia caballi and B. equi, organisms that cause equine piroplasmosis.

Equine piroplasmosis was eradicated officially from Florida (and, thereby, the United States) in 1988, so one of the big questions when these cases popped up was that of its source. As none of the horses on the index premises (the first premises where positive horses were found) was imported, the source of the disease was unclear when the investigation began nearly a month ago.

But Short thinks investigators might have found the source. He said tracing from the index premises led investigators to a barn with two horses that came directly to Florida from Mexico in 2005. Three other horses lived at the farm with these two before they were dispersed to other properties.

"If it doesn't get a lot bigger, and we don't get a lot more positives, it'll all actually tie in fairly neatly to that original premises that those horses came to in 2005," Short said. "Time will tell--we're still investigating a few loose links."

In total, 20 horses in Florida have tested positive for piroplasmosis. Five have been removed, via euthanasia or transfer to the National Veterinary Services Laboratories in Ames, Iowa, for further study. The remaining 15 positive horses live on five premises.

Counties with positive horses include Manatee, DeSoto, Polk, Lake, and Dade.

According to Short, all of these horses are from the local-level "brush track" Quarter Horse racing circuit or are connected directly to that industry.

Because of its foreign animal disease status, the disease's presence in Florida creates a conundrum for other countries and states that typically closely regulate the movement of animals from affected nations. The United States has screened all imported horses for piroplasmosis for nearly 30 years.

While Short said he thinks the actual risk of disease to other horses in Florida is minimal, he said the reaction of other states and countries is "harder to predict."

To Short's knowledge, Canada is so far the only jurisdiction that has said it will not accept horses from Florida.

"Other states are watching very closely," Short added. "They're not going to take action at this point, but we're really going to stay in communication with them and let them know exactly what's going on. There's no indication, at least as of today, that they're going to make any increased restrictions or requirements on Florida horses."

About the Author

Erin Ryder

Erin Ryder is a former news editor of The Horse: Your Guide To Equine Health Care. She owns a portly gray gelding named Duncan and dabbles in several equestrian disciplines, with an emphasis on dressage.

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