Equine piroplasmosis

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Equine Piroplasmosis

Babesiosis, Equine Bilary Fever, Horse Tick Fiver

Equine piroplasmosis (EP) is an infectious, noncontagious, tick-borne disease of horses and other Equidae species. EP is caused by two intra-erythrocytic hemoprotozoans, Babesia caballi and Theileria equi (formally Babesia equi). These hemoprotozoan parasites are found throughout tropical and subtropical areas, and some temperate zones worldwide. Infections with B. caballi are usually less severe than when associated with T. equi. These parasites attack the horse's red blood cells (RBCs) and lymphocytes, leading to hemolytic anemia and associated systemic illness. Anemia is the hallmark manifestation associated with EP in horses. Incidences of EP have been documented worldwide, likely attributed to the frequency of international horse travel.

EP is diagnosed in horses through the use of microscopic examination, indirect immunofluorescent antibody test (IFAT), enzyme-linked immunoassays (ELISA), and polymerase chain reaction (PCR). Two competitive-ELISAs (cELISA) were produced for detecting the antibody to T. equi and B. caballi.

B. caballi and T. equi are transmitted by multiple Ixodid ticks of the genera Boophilus, Dermacentor, Haemaphysalis, Hyalomma and Rhipicephalus. In Europe, Dermacentor reticulatus tick species is the biggest vector of piroplasmosis. Horses are infected through the tick's saliva as it bites down and penetrates the skin to feed on the animal's blood. Another important way horses can become infected with either of the parasites is through blood contaminated needles and syringe reuse, or blood transfusion. Outbreaks have been documented in Germany, Switzerland, and Australia that were caused by contaminated medical equipment.

When horses are infected and later recover from an acute episode of EP, that horse will remain a carrier of the parasite for up to 4 years with B. caballi and for life with T. equi.

Incubation Period
The incubation period for the acute form of the disease by B. caballi infection is 10–30 days and 12 to 19 days for T. equi infection.


Red urine
Weight loss
Loss of appetite
Labored or Rapid breathing
Elevated heart rate
Pale mucous membranes
Leg swelling


  • History - of international travel and tick infestation or blood transfusion.
  • Clinical signs
  • PCR assay
  • cELISA - Considered to be the official test for EP.
  • Complement fixation test (CFT) - Was considered the previous official test for EP, prior to replacement by the cELISA, which is considered to be more reliable.
  • Giemsa-stained blood smear



Report diseaseEP is a reportable disease, meaning that if you suspect that your horse has this disease, by law you need to report it to your veterinarian, or a state or federal veterinarian.
Imidocarb dipropionate (Carbesia)2.2-4 mg/kg administered IM at varying intervals, depending on the parasite the horse is infected with, and whether sterilization is required. The use of this drug is delisted for horses in Europe due to regulations involving horse meat residues. The drug should be used with caution in donkeys, which are susceptible to adverse reactions during treatment.M Meijer
Diminazene aceturate therapy (Berenil)11 mg/kg administered deep IM injections at varying intervals. The use of this drug is only used for the treatment of B. caballi, and has had variable success.M Meijer
Supportive treatmentConsists of administering of IV fluids, blood transfusions, and anti-inflammatory drugsM Meijer


  • Frequently inspect the skin and hair coat of horses for ticks
  • Biosecurity procedures
  • Apply tick repellents to horses


The disease is fatal in up to 50% of previously unexposed animals.

Scientific Research

General Overviews

  • Babesia equi icon
  • Babesia equi icon

Risk Factors

  • International horse travel
  • Living in endemic areas
  • High prevalence of ticks

Causative agent