Equine Piroplasmosis

Equine piroplasmosis (EP) is a tick-borne or blood-borne protozoal disease of equids (horses, donkeys, mules and zebras).

The etiologic agent is one of two protozoan parasites, Theileria equi or Babesia caballi. An organism related to T. equi was described in horses in 2018 and confirmed as a new species, Theileria haneyi. Its clinical significance is currently undetermined.

An equid that survives the clinical phase of the disease continues to carry parasites in red blood cells. These persistently infected equids pose a risk for infection to other equids. The parasites that cause EP are endemic in parts of Africa, the Middle East, Asia, Central and South America, Mexico, the Caribbean, and Europe. The United States is considered free of natural tick-borne transmission of the disease except on the islands of Puerto Rico and the U.S. Virgin Islands.