Fourth Wisconsin Stallion Tests Positive for CEM

A fourth stallion in Wisconsin has tested positive for contagious equine metritis, or CEM, a treatable reproductive disease of horses. One mare has also tested positive in the state. Nationwide, 12 stallions and three mares have been found to be infected.

The National Veterinary Services Laboratories in Ames, Iowa, reported the positive test result earlier this week. The stallion, a 26-year-old Saddlebred housed in Winnebago County, has been quarantined. Like the three stallions that tested positive previously, this one was exposed to the bacterial infection at an artificial insemination center. However, he was not exposed to the Outagamie County stallion that was the first to test positive in Wisconsin.

"While the source of the outbreak is still not known, some have presumed that Nanning, the first CEM-positive stallion we reported in Wisconsin, was the original source. This result makes it clear that he was not," said Wisconsin State Veterinarian Robert Ehlenfeldt, DVM. "This latest infection dates to 2006 and possibly 2005. The first CEM-positive stallion we reported was infected in a different insemination facility, and he was infected in 2007 or later, our investigation shows."


Watch a video interview on contagious equine metritis with Dr. Peter Timoney.
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State and federal animal health personnel have conducted the investigation by examining the breeding records and movement history of each infected horse to find other exposed animals. At each step, any exposed animals are quarantined, tested and treated. Owners of exposed animals are contacted by state or federal animal health officials. There is no need for them to have their animals tested if they have not been contacted.

There is no human health risk and no risk to horses in the general population.

The outbreak began in mid-December, when a Quarter Horse stallion on a Kentucky farm tested positive during routine testing for international semen shipment. Kentucky recently imposed stringent testing requirements for Wisconsin stallions imported for breeding. The investigation now involves at least 608 horses in 45 states, according to the USDA.

CEM is a contagious bacterial infection that passes between mares and stallions during mating. It can also be transmitted on contaminated insemination equipment. Stallions do not suffer any symptoms, but the infection causes inflammation in the mare's uterine lining. This may 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.

For more information about CEM, visit the USDA Web site.

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