The contagious equine metritis (CEM)-affected jack in California is approximately 11 years old and has been owned by the same individual for 10 years since purchased at a local mule event. From purchase until September 1997, he was located in San Diego County, Calif. He was used for breeding by natural service until 1994, when semen collection and artificial insemination was instituted.

In September 1997, he was moved to Sloughhouse, Calif. (Sacramento County) for semen collection, freezing, and export. on approximately Jan. 8, 1998, he was moved to the CEM quarantine facility at UC-Davis, where he is currently housed. Frozen semen from 1991, 1995, and 1997 is available for testing to help estimate the duration of a carrier state.

Due to the informal nature of much of the mule breeding industry, records of both naturally serviced and artificially inseminated mares were not readily available, but were reconstructed from auction and sale records. The records search yielded 27 mares which were bred in 1996 and 1997. Two mares which may have been exposed were sold locally in Northern California and have not thus far been located, but the remaining 25 have been located (22 in California, two in Missouri, and one in Oregon).

On Jan. 2, culture specimen collection for CEM began according to Section V, Veterinary services Memorandum 558.4, which requires three specimens to be taken within seven days on Days 1, 4, and 7, from the mucosal surface of the clitoral fossa and clitoral sinuses (specimens from the endometrium were also taken if that site was accessible). At this time the third set of cultures have been submitted for 15 animals, and all are negative on at least one culture, however, one of the mares (located in Oregon) exposed to the California jack by breeding has tested positive for the CEM-like organism by CF test