National Situation

On December 15, 2008, the State of Kentucky detected a case of Contagious Equine Metritis (CEM) in a 16–year–old quarter horse stallion on a premises in central Kentucky. The clinically healthy stallion was identified during routine testing for semen export.

As of April 20, a total of twenty–one stallions and five mares tested positive for CEM. OPositive stallions were located in Georgia (2), Illinois (3), Indiana (3), Kentucky (4), Texas (1), and Wisconsin (6). Positive mares were located in California (2), Illinois (2) and Wisconsin (1). The epidemiologic investigation is ongoing and no source of the outbreak has been identified.

The epidemiologic investigation currently involves traces to 48 states. For the latest information on the status of the national investigation go to: http://www.aphis.usda.gov/newsroom/hot_issues/cem/index.shtml

California Status

In California, CDFA veterinarians are working with private practitioners to investigate the traces of 43 mares exposed to infected stallions. All exposed mares undergo a USDA testing and treatment protocol. Following a blood test, cultures and treatment, exposed mares are released from quarantine. To date, 38 mares have completed the testing and treatment protocol and have been determined to be negative for Contagious Equine Metritis. The remaining five open cases are pending mare foaling and required post foaling cultures.

In the California investigation of trace exposed mares, a 12–year–old Friesian and a 7 year–old Friesian were confirmed positive for CEM. Both mares have successfully completed the testing and treatment protocol to be classified as free of CEM.

CDFA Press Release #09–010 (02/24/09)

CDFA Press Release #09–006 (01/16/09)

Historic Perspective

The last CEM outbreak in the US was in 2006, when the disease was confirmed in three Lipizzaner stallions imported into the United States from Eastern Europe. The outbreak was limited to these three animals. Prior to 2006, the disease was detected in 1978 on a thoroughbred farm in central Kentucky and in 1979 in Missouri. The disease in both instances was rapidly eradicated. The disease has not been found subsequently in the US horse population.

Contagious Equine Metritis (CEM) is a highly contagious venereal foreign animal disease of horses caused by the bacteria, Taylorella equigenitalis. Transmission occurs during natural cover or artificial insemination breeding. The disease is not known to affect humans or other species of livestock.

Most cases involve non–clinical mares with a mild uterine inflammation. However, an acute infection can cause active inflammation of the endometrium that results in a mucoid vulvar discharge 10–14 days post breeding. Abortions due to CEM are rare. Mares infected during pregnancy can produce subclincal carrier foals. Asymptomatic mares can be infectious and remain carriers for several months. Stallions exhibit no clinical signs but can carry the organism on their external genitalia for an extended period of time.

Carrier mares and stallions act as a reservoir of Taylorella. Undetected mares and stallions are the source of the infection for disease outbreaks. Detection of the carrier state relies on isolation of Taylorella equigenitalis from urogenital swabs of the mare and stallion. Due to the organism’s fastidious nature and slow growth characteristics, it is difficult to culture therefore requires multiple cultures over a period of one week. Serology is available to detect antibodies to CEM in mares. This test cannot be utilized in stallions, as detectable antibodies do not develop.

Mares and stallions with positive cultures for CEM can be successfully treated with appropriate antibiotics.

USDA Web Page

USDA CEM Fact Sheet

USDA Disease Impact Worksheet

Iowa State Disease Fact Sheet