A tick-borne disease known as equine piroplasmosis has been confirmed on a ranch in South Texas. Additional testing is being conducted to determine the extent of infection. Horses on the ranch are quarantined to their premises, and a thorough disease investigation is underway.

Equine piroplasmosis can affect horses, donkeys, mules or zebras and cause clinical signs common to many diseases, including poor appetite and weight loss.

Death losses can occur. Some infected equine animals may exhibit few or no signs of disease. Those animals that survive the acute phase of infection may continue to carry the parasite, which has been identified as Theileria equi (formerly known as Babesia equi), for long periods of time.

“Although equine piroplasmosis is not considered to be endemic in the U.S., cases h ave been detected on occasion,” said Dr. Bob Hillman, Texas’ state veterinarian and head of the Texas Animal Health Commission, the state’s livestock and poultry health regulatory agency. “In June, equine piroplasmosis was detected in Missouri, with a related case found in Kansas. In 2008, the infection was detected in Florida. These cases have been closed.”

“As many as 15 tick species are capable of carrying and transmitting the blood parasite responsible for causing equine piroplasmosis,” Dr. Hillman explained. “At this time, we do not know which species of tick is responsible for transmitting infection on the South Texas ranch. Additional blood and tick samples are being collected and will be submitted for analysis to the National Veterinary Services Laboratory (NVSL) in Ames, Iowa.”

Dr. Hillman said there is no vaccine for equine piroplasmosis, and treatment generally is not effective against this tick-borne infection. To avoid spread of the disease, it is important to eliminate contact with ticks and to prevent the transfer of blood from one equine animal to another.

“Equine owners may want to consult with their veterinarians for recommendations on preventing tick infestation,” said Dr. Hillman. “If equine animals exhibit signs of illness, a veterinarian should be contacted, so appropriate samples may be collected for laboratory testing. Currently, we have no indication that this tick-transmitted disease has occurred at other sites in Texas, but maintaining vigilance for this blood parasite is necessary in determining the extent of this disease situation.”