Two cases of contagious equine metritis (CEM) have been confirmed in the South African province of Gauteng, according to a report from the World Animal Health Information Database. The disease likely originated from an imported stallion released from the government quarantine facility on Feb. 11.

After being released from quarantine, the stallion was transported to a private collection facility, where swabs from him and a test mare were cultured. The U.K.’s Animal Health Veterinary Laboratory Agency confirmed that both swabs were positive for CEM.

A total of 20 horses who came in contact with the stallion are considered at-risk for contracting the disease, and all have been placed under quarantine. The report indicates that all susceptible horses will be monitored and treated, if necessary, for CEM.

Contagious equine metritis is a contagious venereal disease carried by stallions and caused by the bacterium Taylorella equigenitalis. The disease can cause massive economic losses as a result of its devastating effects on reproductive efficiency. These losses are related to affected mares’ inability to become pregnant, fetal loss, and costs related to testing, quarantining, and treatment