Piroplasmosis in Horses

November 23, 2009 (published)

Today I am going to talk about a rare disease in horses called piroplasmosis; it is also called babesiosis. The reason I am even mentioning this disease is that several horses in Florida were recently diagnosed with the disease so it is possible we could see it in horses in Texas, especially since the horses in Florida were imported from Mexico. The disease is caused by the organism Babesia, which is a protozoan parasite that affects red blood cells.

In DVM Magazine, Dr. Donald Knowles indicates symptoms of the disease include fever, malaise, and anemia. Malaise is really a human term that means a general feeling of body discomfort, so in equine terms it describes a horse that just looks like he doesn't feel very well. Anemia is a decrease in red blood cells, which is caused by the parasite destroying the cells. Once infected, some horses may remain carriers for life even if they do not show any symptoms. The protozoans are transmitted by ticks but also can be transmitted from horse to horse by using the same needle for giving injections. This was the mode of transmission in some of the recent Florida cases. The United States, Canada, Australia, Japan, England and Ireland will not allow horses that are positive for piroplasmosis on the blood test to enter, but not all the tests are 100%. Although there is a drug to treat these horses, it is rare to completely clear the infection. Even though recovered horses are clinically normal, they are able to transmit the disease to other horses either through ticks or needles. This is just one reason to control ticks on your horses and to always use a new, sterile needle when giving an injection.

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