The Arizona Department of Agriculture (ADA) has quarantined five horses to a Maricopa County premises after a stallion tested positive for contagious equine metrititis (CEM), a sexually transmitted disease. 

CEM 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, 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 bred to the positive stallion this breeding season. Farm records indicate that semen was shipped to three states.

The four-year-old Arabian 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 frozen semen has been quarantined.

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. There is no evidence that CEM affects people.

Infected and exposed equine animals are being held under movement restrictions by Arizona animal health authorities until veterinary treatment is completed and are certified as CEM-negative.