USDA has now made the rules final.

The U.S. Animal and Plant Health Inspection Service (APHIS) undertook the rulemaking because of the increasing number of cases of CEM in the last few years. The changes are intended to provide additional safeguards and strengthen the testing requirements on imported horses to reduce the chances of a CEM outbreak in the U.S.

Yearlings and weanlings cannot have been bred to other horses, either through artificial insemination or live breeding, from the time they were tested for CEM until export from the CEM country. Test mares, imported mares, and imported stallions above a certain age will be required to undergo an additional CEM test that will help improve the accuracy of final test results. These include:

• Mares over 731 days of age must be given a complement fixation (CF) test at the post-arrival CEM quarantine facility. Mares that test positive will be treated and retested.
• Stallions to be imported will have one set of cultures collected prior to test breeding with negative results. If positive, the stallion will be treated and retested by being test bred to two mares within 21 days of the treatment.
• Test Mares and Mares over 731 days: Three sets of cultures must be taken -- but only the third set must include a swab from the distal cervix or endometrium.

The additional requirements are complicated. Those involved in bringing horses into the U.S. from CEM-affected countries should review the new provisions here.

The new rules are effective March 13, 2013.

Contagious Equine Metritis is a transmissible, exotic venereal disease in horses that causes infertility in mares and can sometimes cause mares to spontaneously abort. Infected stallions exhibit no clinical signs, but can carry the CEM bacteria for years. The disease is commonly transmitted during sexual intercourse, but can also be transmitted indirectly through artificial insemination or contact with contaminated hands or objects. It can be treated with disinfectants and antibiotics.