Contagious Equine Metritis Diagnostic Testing

Contagious equine metritis (CEM), a sexually transmitted equine disease, has cost the horse industry millions of dollars in recent years due to lower fertility in mares. However, diagnostic testing of animals believed infected has helped limit the spread of the disease and effectively eradicated it in some countries.

  1. History

    • CEM was first found in England in 1977 and in the United States in the following year. While the disease is usually transmitted during sexual intercourse, it can also be spread during artificial insemination. Since it can spread rapidly, horses suspected of carrying the disease are quarantined.

    Disease Characteristics

    • While stallions rarely show symptoms of the disease, infected mares will usually have a thick, milky discharge from the uterus 10 to 14 days after breeding. Mares can also be carriers of the disease without showing symptoms. While CEM seldom causes permanent harm to mares, it can make it harder for them to become pregnant.

    Diagnostic Testing

    • According to the USDA there are three methods of testing for the disease: blood tests, bacterial cultures and test breedings. Bacterial cultures are the most common method of diagnosis as the blood tests can only be used on mares that have had the disease long enough to build up antibodies to it. A stallion suspected of having CEM will be bred to a mare that will then be tested for the disease.