What is Contagious Equine Metritis? (CEM) is a non-systemic, venereal disease of equines that causes short-term infertility in mares and rare abortion. The etiological agent is a bacteria, Taylorella equigenitalis transmitted during live cover or artificial insemination. CEM is not endemic in the United States and imported horses are required to test negative prior to importation.
On May 23, 2024, the National Veterinary Services Laboratories (NVSL) in Ames, Iowa, reported confirmation by bacterial culture a positive case of Taylorella equigenitalis, the causative agent of contagious equine metritis (CEM), in an 11-year-old domestic pony mare in central Florida. The mare had been bred by live cover on May 10th to a 3-year-old pony stallion. After breeding, the mare had retained free fluid in her uterus and was treated by uterine lavage on May 13th. The uterine fluid was collected and sent for routine bacterial culture, which ultimately yielded the confirmed positive results for T. equigenitalis. The mare and the stallion are both being held under state quarantine in Florida and the stallion has been sampled for testing at NVSL with results pending. Traceback and epidemiological investigation is ongoing and additional updates will be posted under the “Confirmed CEM Cases in the United States” tab: https://www.aphis.usda.gov/livestock-poultry-disease/equine/contagious-equine-metritis as they become available. Additional resource USDA CEM Factsheet: https://www.aphis.usda.gov/sites/default/files/fsc-cem.pdf;
Clinical Signs
Stallions show no signs of the CEM and serve as carrier animals for spreading the disease. Once the bacteria is introduced to a mare, clinical signs will usually appear 10-14 days later. Clinical signs in the mare include:
- Vaginal discharge
- Infertility
- Abortion
- Mares may become carriers of the organism.
- Foals born to infected/carrier mares may also become long term carriers of the organism.
Diagnosis: Prophylactic annual testing of stallions prior to the breeding season as a means of reducing the risk of spread has been proposed and is recommended by USDA for active breeding stallions. Mares that develop genital discharge or that “short cycle” after breeding to an untested or imported stallion should be considered for evaluation of T. equigenitalis.
Treatment: Treatment consists of thorough washing of the external genitalia in stallions and mares using a disinfectant soap (e.g. 2% Clorhexidine) followed by thorough rinsing and application of a topical antibiotic (e.g. nitrofurazone or silver sulfadiazine). These steps are repeated for five consecutive days. Most horses will respond well to a single series treatment, however some may need retreatment.
Prevention: CEM is not endemic in the United States but may be imported with infected horses. Negative tests are required by USDA for all imported horses.
For more information visit: https://equinediseasecc.org | The Equine Disease Communication Center's website.
