CEM Concerns

Contagious equine metritis in horses.

Contagious equine metritis is a sexually transmitted disease of horses caused by the bacteria Taylorella equigenitalis. Clinical signs of the disease include a copious vaginal discharge in up to 40 percent of affected mares, infertility and abortion. Stallions usually show no clinical signs but can become chronic carriers of the disease and spread it via breeding. The disease can be spread via live cover, semen collected for artificial insemination, contaminated equipment and by the people handling the horses. CEM is treated with disinfectants and antibiotics.

Infected mares and mares imported from CEM-positive countries are required to go through a treatment protocol and remain in quarantine for at least 21 days. Stallions that are infected or imported from a CEM-positive country are quarantined until they are treated and test negative for the disease.

It is important to stay informed about illnesses that can affect your horse. Check out our FREE HYPP report to help stay informed about this hotly debated concern.

To be considered free of CEM, stallions are cultured following treatment and test-bred to CEM-negative mares. The mares are cultured and blood-tested 21 days after breeding. If they are negative, the stallion is considered negative. For clarification purposes, an exposed horse is one that was bred to a CEM-positive horse, either naturally or via artificial insemination, or one that is otherwise exposed, either by being on the same premises or in close contact, to a CEM-positive horse as determined by state and federal animal health officials. CEM Facts

  • The first diagnosed case of CEM was in England in 1977.
  • The first diagnosed cases of CEM in the United States were March 7, 1979, in central Kentucky
  • Countries known to be affected include Austria, Belgium, Bosnia-Herzegovina, Croatia, the Czech Republic, Denmark, Finland, France, Germany, Great Britain, Greece, Guinea-Bissau, Ireland, Italy, Japan, Luxembourg, the former Yugoslavian republic of Macedonia, Montenegro, the Netherlands, Norway, Serbia, the Slovak republic, Slovenia, Sweden and Switzerland.

If you have any questions about CEM, contact your local state veterinarian or the USDA.

HYPP is a devastating illness. Learn more about it in our FREE HYPP report.