Equine Piroplasmosis is a blood-borne protozoal
infection of horses caused by Theileria (Babesia) equi
and/or Babesia caballi. Equine Piroplasmosis is
present in South and Central America, the Caribbean (including Puerto Rico),
Africa, the Middle East, and Eastern and Southern Europe. Only the United
States, Canada, Australia, Japan, and Iceland are not considered to be endemic
areas. Mortality rates for infected horses can reach
50%. Horses infected with EP can be
enrolled in a USDA-APHIS-approved EP treatment program which is frequently
successful at permanently eliminating the infection. EP has not been shown to be zoonotic. EP is considered a foreign animal disease in
the United States and any detection must be reported to the State Veterinarian
and/or the APHIS Veterinary Services Assistant Director.
There are at least 14 tick species in the genera Dermacentor, Hyalomma, Amblyomma, and Rhipicephalus that may be potential natural vectors for spreading T. equi and B. caballi. Ticks must feed on an EP positive horse in order to spread the organism and some tick species can serve as a reservoir transmitting the infection to future generations of ticks through its eggs. The disease can also be spread by iatrogenic means through blood and blood-contaminated equipment. The majority of cases found within the United States have been linked to the use of contaminated medical equipment (needles, syringes, IV sets, tattooing equipment, other medical tools) and/or blood products. Infection may be passed from mares to foals in utero.
Clinical signs are often non-specific and can include:
Horses found positive for Equine Piroplasmosis in the United States must be placed under quarantine and can either enroll in the USDA-APHIS-approved EP treatment program, remain under life-long quarantine, or be euthanized. The USDA-APHIS-approved EP treatment protocol uses high doses of imidocarb dipriopionate to permanently clear the organism from the horse. Treated horses are released from quarantine once all diagnostic tests return to a negative antibody status. Quarantines may last for one or more years as antibody titers take time to reach negative levels.
To prevent iatrogenic spread, never reuse needles, syringes or IV sets, use only new, clean needles with injectable medicines and use only licensed and approved blood products. Blood transfusions should be performed only by licensed veterinarians using donor horses tested negative for equine piroplasmosis and other blood-borne infections like EIA.
Reduce tick exposure by keeping pastures mowed, removing brush and weeds and using topical insecticides such as pyrethroid or permethrin products. There are no vaccines available for EP prevention.