Contagious Equine Metritis

What is Contagious Equine Metritis? 

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 (a fastidious, microaerophilic, Gram-negative coccobacillus) 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. 

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.


July 01, 2024
Confirmed Case(s) - Official Quarantine
June 13, 2024
Orange County, FL
Confirmed Case(s) - Official Quarantine
June 05, 2024
Orange County, FL
Confirmed Case(s) - Official Quarantine