The World Organization for Animal Health reported Wednesday that a 16-year-old Quarter Horse stallion from Woodford, Ky., tested positive for Taylorella equigenitalis.
The venereal infection, also known as contagious equine metritis, was last reported in the U.S. in December 2006.
Test results were confirmed by the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service, which submitted the information to the World Organization for Animal Health.
The stallion was identified as having contagious equine metritis during routine testing for export of semen. An early investigation indicated that the stallion was used for semen collection only and not used for live breeding to mares.
The affected premises has eight other horses, all of whom were reported as clinically healthy. Laboratory samples have been taken from these horses, but the results are pending.
The semen and premises are under an official state quarantine.
The source of the outbreak is under investigation. The Kentucky Department of Agriculture and USDA officials are tracing all shipments of semen from the stallion as well as all horses that visited the premises since the stallion's arrival.