Texas is among 27 states tracing and testing horses that may have been exposed to contagious equine metritis (CEM), a highly contagious disease that can be transmitted during breeding or artificial insemination. CEM can cause temporary infertility of horses. The disease, not known to affect humans, was first detected in the U.S. in 1978, then again in l979. In both instances, the infection was eradicated.

In mid-December 2008, a CEM-infected quarter horse stallion was detected in Kentucky during routine testing for international semen shipment. The USDA and Kentucky animal health authorities quickly initiated an epidemiological investigation, leading to the testing of more horses. To date, seven infected stallions have been detected: four in Kentucky, and three in Indiana. The Indiana stallions had spent part of the 2008 breeding season on the Kentucky premises where the initial CEM case was detected.

As of January 2, 2009, 78 potentially exposed horses (nine stallions and 69 mares) in 27 states have been identified and located, and placed under hold order or quarantine by state animal health authorities, pending test results.

In Texas, veterinarians from the Texas Animal Health Commission (TAHC), the state regulatory agency for livestock health, have contacted the owners of 14 mares and a stallion with epidemiological links to the infected horses. Testing of the 15 horses in Texas will begin the week of January 5. Currently, Texas has no known CEM infection.

As the epidemiological investigation widens, at least 250 additional horses are being traced in more than 25 states.

Dr. Ellis, Texas’ assistant state veterinarian, stressed that CEM is spread by infected equine animals during breeding, not by casual contact or shared boarding facilities. CEM is a venereal disease transmitted by infected stallions either during natural service or through artificial insemination.

CEM-infected horses must be quarantined and treated with disinfectants and antibiotics over a period of several weeks. Following a course of successful treatment and re-evaluation, the animals may be certified CEM-negative and released from quarantine.