Wisconsin Friesian Stallion Positive for CEM

A stallion quarantined in Outagamie County, Wis., has tested positive for contagious equine metritis (CEM), a contagious but treatable reproductive disease of horses.

The National Veterinary Services Laboratories in Ames, Iowa, reported the positive test result Monday afternoon, Jan. 12. The stallion, a 13-year-old Friesian, has been quarantined since Jan. 5, when state animal health authorities learned he had been at a Wisconsin artificial insemination center at the same time as a stallion that later travelled to the index farm in Kentucky.

State and federal animal health personnel will examine the stallion's breeding records and movement history to trace what mares may have been exposed via natural breeding or artificial insemination, and what stallions may have been exposed via shared artificial insemination equipment. Any exposed animals, in Wisconsin or other states, will be quarantined for testing.

Wisconsin State Veterinarian Robert Ehlenfeldt, DVM, stressed that there is no risk to horses in the general population. "There is no reason for horse owners to get horses tested on their own. If our investigation shows that a horse has been exposed, we will notify the owner," he said.

Mare CEM video

Watch the CEM testing and treatment protocol for mares and stallions.

Ehlenfeldt quarantined 17 horses on 11 farms Jan. 5 because they had been exposed to one of seven infected stallions in Kentucky and Indiana. The other 16 are mares. All remain under quarantine, and further testing is pending.

Nationwide, the CEM investigation involves at least 272 horses in 38 states, according to the USDA. The outbreak began in mid-December, when a Quarter Horse stallion on a Kentucky farm tested positive during routine testing for international semen shipment. The initial disease trace found that three more stallions in Kentucky and three in Indiana that had spent time on the original farm were also CEM-positive. The continuing trace has found 23 more stallions in 10 states that had been exposed, and 242 mares in 36 states.

CEM is a contagious bacterial infection that passes between mares and stallions. It can also be transmitted on contaminated insemination equipment. Stallions do not display and clinical signs, but the infection causes inflammation in the mare's uterine lining. This might prevent pregnancy or cause the mare to abort if she becomes pregnant. The disease is treatable with disinfectants and antibiotics.  

CEM is considered a foreign animal disease in the United States. It was first discovered in Europe in 1977, and has appeared in the United States only twice outside quarantine stations where stallions are required to be tested and treated before being released into the country. In 1979, there was an outbreak. In 2006, three Lipizzaner stallions imported into Wisconsin from Eastern Europe tested positive after their arrival, but before they had been used for breeding.

More than 20,500 premises with horses are registered in Wisconsin.

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