In December 1997, the American Horse Council was informed by the Animal and Plant Health Inspection Service of the U.S. Department of Agriculture that an 11 year old donkey jack had unexpectedly cultured positive for a Contagious Equine Metritis-like organism. Later in January, Kentucky reported having cultured a similar organism from two mares and another donkey jack. None of the Kentucky animals has been associated with the California donkey jack.
In California and Kentucky, efforts to identify additional contacts with the affected jacks continue. Any jacks, stallions or mares positive in the Complement Fixation test for CEM or which have cultured positive for the organism are under quarantine. Exposed animals are also quarantined.
The organism that has been cultured from the jacks and several mares is different in a number of respects from a reference strain of the CEM organism [Taylorella Equigenitalis] first isolated in the U.S. in 1978 . It may represent a new species or subspecies of the bacterium. Studies are underway to characterize the organism and determine its pathogenicity.
In 1978, Contagious Equine Metritis (CEM) was diagnosed on farms in Kentucky shortly after the start of the breeding season. The occurrence resulted in several farms being shut down while the infected mares and stallions were treated and cleared of infection. The cost to the industry was estimated at $1 million a day. CEM is considered a considered a disease exotic to the U.S. and the isolation of this CEM-like organism may have serious repercussions on the horse industry in this country.
CEM is a disease that is caused by the bacterium Taylorella Equigenitalis. It is a highly contagious infection that is spread by venereal transmission or through the use of contaminated instruments. Carrier mares or stallions are the reservoir of infection. Foals can be infected following transplacental transmission in the uterus or through exposure to the organism at, or shortly after, foaling.
Because mares and stallions may not show clinical signs of infection, diagnosis depends upon the isolation of T. equigenitalis from the reproductive tract. Serologic testing is of value only for detecting infection in a mare recently infected with CEM. Antibodies are maximally detectable between 15 and 40 days post breeding. Titers can decline rapidly and may disappear as early as six weeks after primary infection. Serologic testing is not a useful diagnostic tool for detection of the carrier state in stallions since they do not develop serum antibodies to the organism.
In mares with clinical signs, an odorless, grayish-white mucopurulent discharge of uterine origin may be seen. Mares may develop an endometritis, cervicitis and vaginitis and return to estrus after a shortened diestrus period. Some mares may show no discharge from the reproductive tract but experience infertility for a few weeks. Strictly speaking stallions are not infected with the bacteria, but harbor it as a surface contaminant on the external genitalia.
Numerous questions remain about this previously unknown strain of T.
equigenitalis. The impact of the isolation of this organism cannot be
determined at this time, although its potential affect could be great.
Expected international repercussions have been mixed. Mexico and Japan
have placed restrictions on U.S. horses (see related story) and other
countries such as New Zealand and Australia have asked for additional
certification on U. S. origin horses.
Current Status
Please see Contagious Equine Metritis Update March 24, 2000
The American Horse Council has been informed by the Export Staff of Veterinary Services of the U.S. Department of Agriculture that Mexico has placed movement restrictions on U.S. horses. All horses, except geldings, over the age of 12 months must be isolated for thirty days and tested for CEM at seven day intervals. Testing requires swabs taken from three separate locations on the animal but the locations were not specified.
The AHC has sought the assistance of the U.S. Department of Agriculture in seeking relief for competition horses who go to events in Mexico and are not used for breeding.
Japan has added CEM requirements for horses imported from the U.S.
Any intact animals, which have been used for breeding, are required to
have 3 sets of cultures taken at seven day intervals during the
pre-export isolation period.
More Information
Questions regarding this information should be directed to Amy W. Mann at the AHC offices,202-296-4031.
For more information on CEM and other equine health issues please visit United States Department of Agriculture's APHIS and American Association of Equine Practitioners web sites.
Copyright © 2000 the American Horse Council.