Piroplasmosis is a tick-born disease of horses caused by the protozoan blood parasites Babesia equi and Babesia caballi. It is present in tropical and subtropical areas such as South America, parts of Africa, and Asia. Presently, the U.S. requires negative tests before allowing the import of horses.
Once infected, a horse can take 7 to 22 days to show signs of illness. Signs are variable. Horses that contract the disease for the first time as adults are more seriously affected. Fever, depression and weakness are common signs. Jaundice and blood splotches on the gums, conjunctiva and vulva, and bloody urine are often seen. Most horses recover from the acute stage to develop an immunity and become carriers of the parasite.
In those areas where the disease is permanently present, foals are born with passive immunity which protects them from the acute disease. However, they become infected and become carriers. The carrier animal remains in normal health unless stress, either of travel or competition type, causes the acute disease.
Diagnosis is made through a microscopic examination. In acute stage the goal is to reduce the fever and prevent any further destruction of the red blood cells. There are several anti-protozoan drugs that can be used for this purpose. It is more difficult to eradicate babesia from the system in the chronic carrier case. Imidocarb dipropionate appears to be effective in eliminating the Babesia infection. Some horses treated with imidocarb dipropionate and a blood transfusion often recover from the blood crisis. If a horse develops serious complications such as hepatitis, pancreatitis,, acute kidney failure, and extensive blood clotting the prognosis is poor.