CEM Investigation: 23 Positive Stallions

A stallion in Wisconsin has become positive stallion No. 23 in an ongoing investigation into contagious equine metritis (CEM).

Wisconsin State Veterinarian Robert Ehlenfeldt, DVM, said this horse is considered part of the outbreak that was first discovered in 2008 because he has the same strain of causative bacterium Taylorella equigenitalis as the other horses associated with that investigation.

He said the horse was probably exposed to T. equigenitalis during collection at a Wisconsin artificial insemination station in 2008, but was just recently identified because the owner did not want the animal to be tested.

"He has been under quarantine for an extensive period with an owner who was reluctant to test him," Ehlenfeldt explained.

Other positive stallions had been collected at the same facility, so this positive case came as no surprise to public officials, said James Barrett, public affairs specialist at the USDA.

Barrett said the extensive outbreak was winding down. In addition to the 23 positive stallions and five positive mares, another 966 horses were exposed to T. equigenitalis (read more).

"We are down to a few horses that have yet to go through treatment or testing," Barrett said. "The majority of horses that were either positive or exposed have been tested and treated."

Georgia, Indiana, Iowa, and Kentucky, are now considered free of CEM because they have completed testing and treatment of all known positive and exposed horses, Barrett said.

CEM is a highly contagious venereal disease that can cause infertility and, in rare cases, abortion. It can also exist subclinically.

"It's a sneaky disease and it is difficult to detect and treat," Barrett said. "Luckily, both mares and stallions can be successfully treated with topical and systemic antibiotics."

Although the United States has suffered outbreaks and isolated cases, the country is considered free of CEM. Barrett said the next step was to test horses that have not been associated with the positive horses.

"We've been spending our time finding out which horses were exposed and which are positive," Barrett said. "Now, we are moving to horses that we know are not associated with these horses just to be sure it is not endemic in this country. We want to increase international confidence that we are CEM free."

Horses will continue to be tested upon entry into the Untied States following the existing standards for testing to prevent another outbreak from occurring, he noted.

About the Author

Marie Rosenthal, MS

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