A ranch in Kleberg County, Texas, is under quarantine after a 7-year-old Quarter Horse mare became ill and tested positive for equine piroplasmosis earlier this month. An additional 31 horses on the ranch have also tested positive. An Oct. 20 report issued to the World Organization for Animal Health by John Clifford, DVM, deputy administrator of the USDA’s Animal and Plant Health Inspection Service, gives new details on the situation.

The index mare was presented to a local veterinary hospital on Oct. 2, the reported noted. Veterinarians suspected a blood-borne pathogen and isolated the mare. Positive test results for equine piroplasmosis were received on Oct. 12. The following day, the Texas Animal Health Commission quarantined the ranch and tested 31 horses epidemiologically linked with the index animal for equine piroplasmosis. Investigators also collected ticks from five horses for testing and species identification.

On Oct. 19 investigators received positive test results for causative organism Theileria equi from the National Veterinary Services Laboratory on the 31 exposed horses, as well as the index case. An additional 96 horses were then tested, with results pending. Results of the tick investigation are also pending.

The report listed the origin of this infection as unknown or inconclusive