05/03/2025
Equine piroplasmosis.
Equine piroplasmosis (EP) blood-borne disease caused by protozoal parasites Theileria equi or Babesia caballi. The disease is spread primarily by ticks. It can affect horses, donkeys, mules, and zebras. Mortality rates for infected horses can reach 50 percent. EP is a foreign animal disease. All detections must be reported to State and Federal animal health officials.
EP is endemic in tropical and temperate areas of the world with ticks capable of carrying the disease, including South and Central America, the Caribbean, Africa, the Middle East, and Eastern and Southern Europe. Horses presented for import into the United States must test negative for T. equi and B. caballi. In the United States, EP is endemic in Puerto Rico and the U.S. Virgin Islands. Isolated outbreaks have occurred on the U.S. mainland.
In most cases, an EP-infected horse can take 10 to 30 days to show signs of the disease. It may not affect all horses equally.
Horses with a mild case of EP typically have:
Reduced appetite or lack of appetite
Weakness or exercise intolerance
Horses with more severe cases may have:
Fever
Anemia
Jaundice (yellow discoloration of mucous membranes)
Weight loss
Labored breathing
Swollen abdomen
Colic
Sudden death
Horses that survive the initial signs of the disease become chronic lifelong carriers and may show no further signs.
How It Is Treated
Historically, EP-infected animals were euthanized, exported from the United States, or quarantined for the rest of their lives. Today, APHIS offers a treatment program for EP-infected horses. An accredited veterinarian performs the treatment, with oversight from State and Federal animal health officials. This program has been successful in clearing most horses of infection over time. Treated horses are released from quarantine once they test negative for EP.
How To Prevent This Disease
EP is most often spread in the United States through blood and blood-contaminated equipment. Certain species of ticks can also spread EP, particularly in countries where the disease is widespread. Ticks become infected when they ingest blood from infected equines. The ticks then spread it by biting uninfected equines.
There is no vaccine. To prevent the spread of EP:
Never reuse needles, syringes or IV sets.
Only use new, clean needles with injectable medicines.
Only use licensed and approved blood products.
Make sure blood transfusions are performed only by licensed veterinarians using donor horses that have tested negative for EP and other blood-borne diseases like equine infectious anemia.
Regularly check your horses for ticks. If you are in a tick-infested area, use tick repellant products to protect your horses.
Reduce tick exposure by routinely mowing pastures and removing brush and weeds.
Dr. Muhammad Rome
Dvm RVMP.