What is Piroplasmosis?

Equine Piroplasmosis or Babesiosis is a protozoal disease that infects the red blood cells (RBC’s) of horses, donkeys, mules and zebras (please see figure 1). The disease is caused by two related organisms, Babesia equi and Babesia caballi. Protozoa are complex parasites andare primarily transmitted to  horses by ticks, but the organisms may be spread mechanically from animal to animal by contaminated needles. In addition, the disease can also be spread from pregnant mares to foals during pregnancy.

Signs and Symptoms

Clinical signs horses infected with Babesia spp. are related to a loss of RBC numbers and include:

  • Fever
  • Anemia
  • Jaundiced (yellow) mucous membranes
  • Distended abdomen
  • Labored breathing

These signs are extremely variable as some infected horses may show no signs of illness and while in other horses the disease may be fatal. The clinical signs of Piroplasmosis generally become evident within 7 to 22 days. In many cases the disease can be treated, but there is currently no cure for Babesiosis; horses remain infected for life. In addition, there is not a vaccine that will prevent the disease.

Geographical presence

Babesiosis is found most commonly in South and Central America, the Caribbean (including Puerto Rico), Africa, the Middle East, and Eastern and Southern Europe. At this time, the United States, Canada, Australia, Japan, England and Ireland are not considered to be countries with a significant amount of the disease within its borders. Piroplasmosis was eradicated from the US in 1988; however, approximately 2 years ago it was discovered in a herd of horses in South Texas. Since that time, horses with Piroplasmosis have also been identified in Kansas, Missouri, New Mexico and Florida. In Florida, the tick population has been screened for the disease and no ticks have been found to be positive for Babesia spp.

Investigators have identified that the greatest risk of a horse acquiring the disease is from contact with an infected horse during international equestrian competitions. During these events, the spread of this disease is prevented by properly cleaning and disinfecting equine medical equipment and providing tick and fly control on the premises and in the stable area.

If you concerned that your horse may have Babesiosis, your veterinarian can obtain a blood sample from your horse and submit it to a certified laboratory for analysis. Many states now require horses to be tested for the disease before they can be transported into or out of the state.

Figure 1

Figure 1 demonstrates the presence of the protozoa within the equine red blood cell.

Please contact you veterinarian for information about the transportation and testing requirements for Piroplasmosis if you are going to transport your horses out-of-state.

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