State and federal agriculture officials are investigating a case of contagious equine metritis (CEM) in a Quarter Horse in Central Kentucky.

The 16-year-old stallion tested positive for CEM during routine testing on Dec. 10. The test was performed by the University of Kentucky Livestock Disease Diagnostic Center as a preliminary step to shipping frozen semen to the European Union. Samples were sent to the National Veterinary Services Laboratories in Ames, Iowa, which confirmed the diagnosis on Monday.

The index horse and all exposed horses are under quarantine and undergoing testing protocols. The index horse is being treated, and exposed horses have been tested to see if they are infected.

The index horse was moved to Kentucky in February from Texas, where he had been located for his entire breeding career. All breeding was done artificially with no history of natural service.

During the 2008 breeding season, 22 stallions from various states were bred on the farm. Thirteen of the stallions were relocated to other states, and one was relocated to another facility in Kentucky. The index stallion was bred to 44 mares both on the farm and by shipped semen.

Contagious equine metritis (CEM) is a transmissible, exotic venereal disease in horses. It usually results in infertility in mares and, on rare occasions, can cause mares to spontaneously abort. Infected stallions exhibit no clinical signs but can carry the CEM bacteria for years. CEM is commonly transmitted during sexual intercourse but also might be transmitted indirectly through artificial insemination or contact with contaminated hands or objects.

There is no evidence that CEM affects people.

CEM can be treated with disinfectants and antibiotics. In Kentucky, CEM-positive mares and mares from CEM-positive countries are required by state regulations to go through a treatment protocol and remain in quarantine for no less than 21 days. Stallions in Kentucky that have CEM or come from a CEM-positive country also are required to remain quarantined until a treatment protocol is completed and they test negative for the disease.

The first cases of CEM in the United States were diagnosed in central Kentucky in 1978. Another outbreak occurred in Missouri in 1979. The disease was eradicated rapidly in both outbreaks.

Kentucky’s horse industry has a total estimated economic impact of $4 billion a year, according to a 2005 study by the American Horse Council. The horse industry generates an estimated 80,000-100,000 jobs, and another 14,000 jobs come from tourism businesses related to the horse industry. Kentucky farm cash receipts for equine, including stud fees, are estimated at $900 million for 2008