Foreign Disease Equine Piroplasmosis Found in Five Florida Horses

Equine piroplasmosis was eradicated officially from Florida (and, thereby, the United States) in 1988. So it came as a shock to many people in the equine industry to hear that a horse in Florida was confirmed positive for the disease last week.

Now animal health officials are working to trace the source of this disease flare-up and contain it.

According to Mike Short, DVM, equine programs manager for Florida's Division of Animal Industry, one horse showing clinical signs of a "hemodynamic crisis" was admitted to an Ocala-area equine hospital last week. The horse was anemic, had low platelets, and was showing signs of kidney problems, depression, and weight loss. A veterinary resident there suspected piroplasmosis after examining a blood slide. Hospital staff isolated the horse and alerted state animal health officials, who are now investigating.

What they've found in tracing back the horse is a property in Manatee County, Fla., housing 22 horses. Four of these horses--animals that were kept in a barn with the affected animal--are positive for equine piroplasmosis.

The one animal that was ill has been euthanized.

So, why is this a big deal?

Equine piroplasmosis (EP) is a tick-borne disease caused by two parasites, Babesia caballi and B. equi. The parasites are able to hitch a ride on certain ticks, in which they can amplify, thus, creating the potential for spread to horses. The parasites can also be spread via shared needles.

Piroplasmosis occurs through much of the world. Areas not considered endemic include the United States, Canada, Australia, Japan, England, Iceland, and Ireland. Horses that get EP might have a fever, anemia, jaundice, hemoglobinuria (the presence in urine of a protein normally found in red blood cells), central nervous system disturbances, and they sometimes die. But some infected horses are less severely affected and might show few or no clinical signs. These horses have the potential to carry the parasites for prolonged periods, during which they are potential sources of infection.

To prevent EP from entering the country, the USDA currently tests all imported horses for antibodies during quarantine. Horses with antibodies to B. caballi and/or B. equi are not allowed entry into the United States.

The only current treatment is a potent type of chemotherapy that should eliminate clinical signs of disease; however, it won't necessarily eliminate the parasites from infected horses.

There are three big questions raised by the current cases: where did the disease come from, is it likely to spread, and what should be done with the positive horses?

Short said the question of where this came from could be difficult to answer, but animal health officials are working with the horses' owners to get solid information and a timeline on the horses' points of origin and dates of transport.

According to Short, the affected horses are Quarter Horses that run on local "brush tracks." Short said it appears they originally came from sanctioned Quarter Horse racing circuits, but the owners' records lack some details on when and from where each horse came to the property. Officials are working with the owners to try to trace the horses back to their origins.

Short said, based on testing, it appears two of the positive horses have been infected longer than the others.

"I don't know that we're ever going to figure out what the source was, but we might," Short said. "We're working on it."

At this point, it appears that the organisms are contained to the original farm. Tests on five horses on a neighboring property thus far are negative.

Because the parasites can be transmitted via shared needles or some species of ticks, animal health officials are monitoring and testing ticks on the affected property and in the area.

So far they have collected and tested 20 ticks. All the ticks they've found have been Gulf Coast ticks, which are a species not considered to be a competent vector to carry the causative organisms, Short said. Tick monitoring and eradication efforts are continuing.

According to Short, it seems most likely that the disease was passed on the affected property via shared needles and other management practices used there. "Some of the practices that we know have gone on (at the affected property) really would be prime to transmit the organism," Short said.

Florida animal health officials and the animals' owners are now faced with the question of what to do with the remaining four positive horses. "Certainly, they're going to be in long-term quarantine, depending on what the owner elects to do," Short said. "Euthanasia's an option. I don't think at this point we're going to require that, but treatment is difficult, it's expensive, and it can be hard on the horse--and there's no guarantee that it would even work. I'm not sure what the owner's going to elect to do, but no matter what it's certainly going to be a long-term quarantine."

With the exception of the quarantined premises, there are no equine movement restrictions in Florida or between Florida and other states. Horses entering Florida from other countries with equine piroplasmosis will continue to be tested prior to and following entry, in accordance with the current rule.

Horse owners are asked to report any unusual clinical signs to their veterinarians, and to use commercially available topical tick repellent products if your horse is in an area where ticks are a problem. Include an avermectin product in your deworming program to provide systemic treatment for ticks.

"We're going to really do a thorough job of tick trappings and tick drags and tick checks," Short said. "We've asked practitioners to report any clinical signs and to submit any ticks they find on horses. It'll be interesting to see what we get here in the next few weeks."

Horse owners are also reminded not to reuse needles among different animals while administering any medications or vaccinations.

The take-home message so far? Although it's surprising to see a disease that's been gone for 20 years pop up, it appears to be an isolated event.

"The positive news out of this is that so far we haven't found any exotic ticks or any ticks known to transmit the disease," Short said. "So far there's only one premises with positives or clinical signs.

"I think potentially this could have a decent ending, but we'll just have to see," he added.

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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