Piroplasmosis In Missouri
Equine piroplasmosis, a foreign reportable disease, has been identified in a horse in Missouri. On June 2, the affected horse (a seven-year-old Quarter Horse) was presented to an equine hospital with signs consistent with a bloodborne disease (although the exact signs have not been reported). The horse was isolated because of the potential for piroplasmosis, and an investigation was started. The sick horse and other horses from the same farm were examined for ticks (the vector of piroplasmosis) and none were found. On June 10, the diagnosis of equine piroplasmosis was confirmed. The other 63 horses on the farm are currently being tested, the results are pending.
No source of infection has yet been suggested. The US was considered free of piroplasmosis after the last horse in a Florida outbreak cleared the infection earlier this year. This newly affected horse was apparently purchased six months ago, but no information was provided about where it came from. The lack of a clear source of infection is concerning because it could indicate that there are unknown cases somewhere else in the US.
Piroplasmosis is a tickborne disease cause by the protozoal parasite Theileria equi. It can cause signs of illness such as fever, anemia (decreased red blood cell count), jaundice, respiratory signs, reddish urine and weight loss. Up to 20% of affected horses may die. The parasite is naturally transmitted by ticks. It can also be transmitted through the re-use of needles or other blood-contaminated medical equipment, and perhaps through breeding if the semen contains blood. One problem with identification and control of piroplasmosis is that many infected horses show no signs of disease. Further, horses that recover can carry the parasite for prolonged periods of time and become long-term sources of infection for other horses, if the appropriate ticks are around to transmit the pathogen. Horses that are carrying this parasite therefore need to be strictly quarantined. Horses that become persistent carriers of piroplasmosis need to be quarantined for life, euthanized or sent to a country where the disease is endemic. More information about the source of infection in this case and how far it has spread is anxiously awaited.
