New Contagious Equine Metritis Case in California

Up until 2008, the United States had been considered free of Contagious Equine Metritis (CEM) for years. However, the disease made a comeback in late 2008, and another case was found in California in May of 2010. According to a press release from the United States Department of Agriculture (USDA) in December of 2008, eight stallions on a central Kentucky farm and another in Wisconsin were diagnosed with the disease. Subsequent to their diagnosis, the locations of over 300 horses exposed to CEM were confirmed in 39 states. in May 2010, the United States Department of Agriculture's (USDA) Animal and Plant Health Inspection Service (APHIS) announced that a new case was found in an Arabian stallion located in Southern California. The stallion had been imported from an undisclosed country not known to be affected by CEM, but investigation of the case determined that he was infected before his arrival in the United States.

Contagious Equine Metritis is a highly contagious venereal disease found in equids-horses, donkeys, mules, etc.-caused by the bacteria Taylorella equigenitalis. CEM is not deadly to adult horses, but it can cause short-term infertility and, rarely, spontaneous abortions in mares. It can sometimes cause endometritis and a vaginal discharge. Stallions are not really affected by the disease, merely carrying the bacteria and passing it on during breeding. Although it is technically only transmissible during breeding, it is also possible for the bacteria to spread through the use of contaminated objects on breeding horses, so only sterilized instruments should be used.

In order to prevent the spread of CEM, the USDA set forth procedures that all of the states are following. A 21-day quarantine is required for horses that have been exposed, along with a series of tests that include vaginal swabs and cultures. Because of the difficulty in isolating Taylorella equigenitalis, testing is a tricky process that takes 12 days to ensure accurate results. Because the testing protocol bears some risk to pregnant mares and their foals, horse owners have the option of keeping pregnant mares in quarantine and delaying testing until after foaling. Affected animals can be cured with antibiotics.

"There's no reason for panic," said Dr. Paul Anderson, Assistant Director of the Minnesota Board of Animal Health, during the 2008 outbreak. He noted that the disease will not spread as long as the proper precautions are taken. "We don't want to alarm people unnecessarily."

Anderson reported that good communication among the USDA, veterinarians and horse owners helped to keep CEM in check. "The horse industry, to their credit, keeps good records as a rule. It helps a great deal." With thorough breeding records, veterinarians are able to trace mares exposed to affected stallions so they can be quarantined and tested, and during the 2008 outbreak, many were tested negative for the disease, but 23 stallions and five mares were tested positive. In total, 1,005 affected horses were found scattered throughout the country.In the current California case, all five of the stallions exposed to the affected stallion were tested negative, and the horse that was originally affected successfully completed his treatment and is no longer affected nor contagious. Testing of the 18 exposed mares is ongoing and will not be completed until after the six that were pregnant mares have their foals in spring of 2011. The other 12 have completed all testing and treatment. The mares are located throughout multiple states.

For more information on Contagious Equine Metritis, visit the USDA website at http://www.aphis.usda.gov/.