Equine Piroplasmosis - Fact Sheet

What is equine piroplasmosis?

Equine piroplasmosis is a tick-borne disease, affecting all equine species, such as horses, mules, donkeys and zebras.

Is equine piroplasmosis a risk to human health?

Human disease due to equine piroplasmosis is very rare. Infected horses pose no risk to humans. Ticks infected with the parasite can spread the disease to humans through biting, although in healthy individuals, infections tend to be mild and self-limiting. Symptoms include tiredness, loss of appetite, general malaise, muscle aches and headaches.

What are the clinical signs of equine piroplasmosis?

The clinical signs of equine piroplasmosis are variable and often non-specific; the disease can easily be confused with other conditions. Equine piroplasmosis can occur in per-acute, acute, sub-acute and chronic forms.

Per-acute: In some per-acute cases, animals may be found dead with no previous signs of disease.

Acute: More often equine piroplasmosis is seen in the acute form characterized by fever, loss of appetite, sudden onset of immobility and reluctance to move, and severe depression. The fever may subside after one day and become intermittent. Other signs include anaemia, jaundice and an enlarged spleen and liver.

Sub-acute: Clinical signs in sub-acute cases are similar to acute cases except that affected animals may show weight loss and an intermittent fever.

Chronic: Chronic cases usually present non-specific clinical signs such as mild loss of appetite, poor performance and loss of body weight. Severe cases can result in death. In young horses and newborn foals the symptoms are more severe.

Where is equine piroplasmosis found?

Equine piroplasmosis has never been found in Canada. It primarily occurs throughout the tropics and subtropics.

How is equine piroplasmosis transmitted and spread?

Equine piroplasmosis is caused by two single-celled (protozoal) organisms, Theileria equi (T. equi) and Babesia caballi (B. caballi). The protozoa invade the red blood cells of infected animals, leading to disease.

The disease is not directly contagious. Rather it is transferred by blood from an infected animal to a susceptible animal or insect. Ticks are the main method of transmission as they are a natural host for the parasites. It can also be transmitted by contaminated needles and syringes. Foals can become infected while in the uterus, particularly with T. equi.

After recovery, horses can carry the parasite in their blood for a long time and can act as sources of infection for ticks. Introduction of carrier animals into disease-free areas, where ticks are prevalent, can lead to a large number of animals becoming infected.

Infection is seasonal and is most likely to occur shortly after peaks in the tick population. Of the climatic factors, temperature is the most important as higher temperatures increase tick activity.

The main risk factor for introducing equine piroplasmosis into Canada is through the importation of infected animals.

How is equine piroplasmosis diagnosed?

The disease is suspected in horses that have anaemia, jaundice or fever. Laboratory and blood tests are necessary for a definitive diagnosis.

How is equine piroplasmosis treated?

Equine piroplasmosis does not respond well to treatment.

While specific antibiotics have been used to treat B. caballi, the toxicity of the drugs may cause the horses to become quite ill during treatment. Side effects include colic, hypersalivation and death.

The currently available treatments are ineffective in clearing T. equi from carriers.

What is done to protect Canadian livestock from equine piroplasmosis?

The Canadian Food Inspection Agency (CFIA) imposes strict regulations on the import of animals and animal products from countries where equine piroplasmosis is known to occur. These regulations are enforced through port-of-entry inspections done by both the CFIA and Canada Border Services Agency.

Equine piroplasmosis is a "reportable disease" under the Health of Animals Act. This means that all suspected cases must be reported to the CFIA for immediate investigation by inspectors.

How would the CFIA respond to an outbreak of equine piroplasmosis in Canada?

Canada's emergency response strategy to an outbreak of equine piroplasmosis would be to:

  • eradicate the disease; and
  • re-establish Canada's disease-free status as quickly as possible.

In an effort to eradicate equine piroplasmosis, the CFIA may employ some or all of the following disease control methods:

  • the humane destruction of infected animals;
  • surveillance and tracing of potentially infected or exposed animals;
  • strict quarantine and animal movement controls to prevent spread; and
  • zoning to define infected and disease-free areas.

Additional information

Date modified: