On October 19th, the National Veterinary Services Laboratories (NVSL) confirmed Equine Piroplasmosis in 32 working Quarter Horses located on a ranch in Kleberg County, Texas. Since this event, the World Organization for Animal Health (OIE) has been coordinating follow-up investigations by the USDA Animal and Plant Inspection Service (APHIS) and is releasing a weekly report.
The latest weekly report has revealed that 357 horses which are directly linked to the "index premises" have been confirmed as being infected with the bacteria. These horses either currently live on the index premises or immediately adjacent to the premises, or boarded temporarily at the premises. The report confirms that infected horses are located across 13 states, including Texas, Alabama, California, Florida, Georgia, Indiana, Louisiana, Minnesota, North Carolina, New Jersey, Tennessee, Utah and Wisconsin. All known piroplasmosis-positive horses are now under quarantine.
The latest report has identified three confirmed cases which are not directly linked to the ongoing investigation. The horses were identified as a result of an enhanced screening program at race tracks in New Jersey, in which over 1000 horses have been tested for Equine Piroplasmosis. The horses in question were tested at Sunland Park Racetrack and were subsequently not allowed to enter. Initial investigation has concluded that transmission of the organism may have resulted from management practices (such as use of shared needles between horses) rather than by the more common tick vector, and that the infections are not epidemiologically linked to the Texas equine piroplasmosis outbreak.
Equine piroplasmosis is an infectious disease spread by ticks which transmit the protozoan parasites Theileria equi and Babesia caballi. Equine piroplasmosis affects all horse species including horses, donkeys and zebras and only a few countries are not considered endemically infected, including Canada, the United States, the United Kingdom and Ireland. The case fatality rate for piroplasmosis-infected horses can approach 50%, and the only treatment is a very stringent chemotherapy which can have serious side effects.