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Three confirmed outbreak sites of Contagious Equine Metritis (CEM), affecting 50+ horses per site with hundreds exposed, have been reported in Orange County, Florida in the timeframe of early Summer 2024 through March 11, 2025. CEM is a highly contagious venereal disease in horses that can lead to short-term infertility in mares and, in rare cases, abortion. While the disease is not endemic to the United States, cases like these highlight the importance of proactive testing and biosecurity measures in breeding operations.
What is Contagious Equine Metritis?
CEM is caused by the bacterium Taylorella equigenitalis, which is transmitted primarily through live cover breeding but can also be spread via contaminated equipment used in artificial insemination. The disease is non-systemic, meaning it does not spread throughout the body, but it can have serious reproductive consequences.
Clinical Signs
Stallions infected with CEM typically show no symptoms, making them silent carriers of the bacteria. Mares, however, may develop clinical signs within 10-14 days of exposure, including:
- Vaginal discharge
- Infertility
- Abortion (rare cases)
Infected mares may also become long-term carriers of the organism, and foals born to these mares can harbor the bacteria, posing a risk of further spread.
Diagnosis and Testing
Routine testing is essential for controlling the spread of CEM. The USDA recommends annual prophylactic testing of active breeding stallions prior to the breeding season. Mares experiencing reproductive issues, such as abnormal discharge or failure to conceive after breeding to an untested or imported stallion, should be evaluated for CEM.
Treatment
CEM is treatable, but affected horses require careful management to prevent reinfection. Treatment typically involves:
- Thorough cleaning of external genitalia with a disinfectant soap (e.g., 2% chlorhexidine) for five consecutive days
- Application of a topical antibiotic (e.g., nitrofurazone or silver sulfadiazine)
- Retesting to confirm successful elimination of the bacteria
Most horses respond well to a single treatment regimen, but some may require additional rounds of treatment.
Prevention and Biosecurity Measures
Since CEM is not endemic in the United States, preventing its introduction is critical. The USDA requires negative CEM testing for all imported horses to minimize the risk of disease spread. Additional precautions for breeding facilities include:
- Routine testing of stallions and mares before breeding
- Strict biosecurity protocols for breeding and reproductive procedures
- Quarantining and testing imported horses before introducing them to a breeding program
What This Means for Horse Owners
The confirmation of CEM cases in Florida serves as a reminder of the importance of disease prevention in equine breeding. Owners should work closely with their veterinarians to ensure proper testing, treatment, and biosecurity protocols are in place to protect their breeding stock and the broader equine community.
As new information becomes available regarding the current cases, horse owners and breeding professionals should stay informed and take proactive measures to minimize the risk of transmission. For active disease alerts, please visit the EDCC, here.