Contagious equine metritis (CEM) is a sexually transmitted disease that can be spread by direct contact during breeding or by contact with contaminated tools and infected semen.
It is important for horse owners, especially breeders, to know the signs of EMF and to quarantine horses if necessary.
Key takeaways
- Contagious equine metritis is a sexually transmitted disease of horses.
- Mares infected with CEM may have vaginal discharge or show no symptoms. Stallions are almost always asymptomatic (show no symptoms).
- CEM prevention involves strict testing and quarantine protocols for imported horses and breeding programs.
- Treatment involves a course of topical antibiotics.
- EMC is a notifiable exotic animal disease.
What is contagious equine metritis?
Contagious equine metritis is a venereal disease of horses caused by the bacteria Equigenital Taylorella. Since it is a sexually transmitted infection, breeding mares and stallions are at greatest risk.
Historically, CEM has caused significant economic losses to the equine industry in the United States. As a result, the United States Department of Agriculture (USDA) has implemented strict testing and quarantine procedures to help prevent outbreaks. EMC is also considered an exotic animal disease, meaning it is very rare in the United States and any cases should be reported to veterinary health authorities.
Symptoms of contagious equine metritis
CEM is a disease limited to the reproductive tract of mares and stallions. In stallions, symptoms are rare. In mares, symptoms are usually mild and self-limiting, so they go away on their own.
The biggest concern regarding CEM is that mares, stallions and even foals born to infected mares can be asymptomatic carriers and continue to spread the disease.
Infected mares may exhibit the following symptoms:
What causes contagious equine metritis?
The bacteria Equigenital Taylorella can be transmitted in the following ways:
How to test for contagious equine metritis?
Two tests are used to diagnose CEM:
Treatment of contagious equine metritis
If a horse tests positive for CEM, treatment is carried out under the direction and supervision of a state veterinarian. Horses must be quarantined to prevent the spread of disease until they have cleared it.
​​​​​Antibiotics are usually used topically for five days. At the end of the treatment period, horses are retested to confirm they are negative before being released from quarantine.
Recovery and Management of Contagious Equine Metritis
Once the infection is treated with antibiotics and the horse tests negative, there are rarely any long-term complications and fertility appears to return to normal after treatment.
Prevention of contagious equine metritis
Following USDA guidelines for testing and quarantining is the first line of defense against CEM. This means testing all imported mares, stallions and semen samples.
Horse breeders must test their stallions annually before breeding and keep complete breeding records in the event of an outbreak.
Veterinarians and breeding establishments should practice good disinfection and sterilization between breeding, collections and artificial inseminations.
Finally, horse owners and breeders should immediately report any new vaginal discharge or fertility problems to their veterinarian.
