Arizona Stallion Reported Positive for CEM

The Arizona Department of Agriculture (ADA) announced today (July 26) the quarantine of five horses on a Maricopa County premises after a stallion tested positive for contagious equine metrititis (CEM), a sexually transmitted disease. The disease can cause spontaneous abortion and infertility in mares.

"This disease can be carried by stallions and mares, and transmitted even through modern breeding practices of artificial insemination and embryo transfer," said John Hunt, DVM, ADA associate director for animal services. "Because many animals don't show symptoms, CEM can be difficult to detect and control."

The state is working with federal partners to trace mares that were bred to the positive stallion--a 4-year-old Arabian--this breeding season. Farm records indicate that the stallion's semen was shipped to three states (at press time the three states had not yet been reported). The stallion was tested as part of a protocol to allow international shipment of semen. All semen collection has been suspended from the quarantined stallions and all currently frozen semen has been quarantined, as well.

A highly contagious venereal infection of all equids, CEM is caused by the bacterium Taylorella equigenitalis and 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. The disease is commonly transmitted during sexual intercourse but also might be transmitted indirectly through artificial insemination or contact with contaminated hands or objects.

The disease can be spread among stallions if strict cleanliness standards are not maintained during the collection of semen. The disease can be treated with antibiotics, and there is no evidence that CEM affects people.

Infected and exposed equine animals are being held under movement restrictions by state animal health authorities until they complete veterinary evaluation and treatment and are certified as CEM-negative. will continue to update the situation as more information becomes available.

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