Probe continues into CEM outbreak

National Report — Federal and state veterinary officials continue to look for the source of an outbreak of contagious equine metritis (CEM) that now affects at least 575 horses in 45 states.

Since the first confirmed case, in a Quarter Horse stallion in Kentucky on Dec. 15, a total of 11 stallions and two mares have been confirmed positive for Taylorella equigenitalis, the causative organism for the reproductive disease that is transmitted through natural breeding or artificial insemination.

The positive stallions, all identified by the USDA's National Veterinary Services Laboratories, include three in Indiana, four in Kentucky, one in Texas and three in Wisconsin. One of the positive mares is in Wisconsin and the other in Illinois, according to USDA's Animal and Plant Health Inspection Service (APHIS).

None of the positive horses can positively be identified as the source of the outbreak, officials emphasize.

The Texas and Indiana stallions were on the central Kentucky premises during the 2008 breeding season. The Wisconsin stallions, while never in Kentucky, were co-located during at least one Wisconsin breeding season with one of the positive stallions that had been on the Kentucky site in 2008. The positive Wisconsin mare was bred to one of the positive stallions in Wisconsin. The positive Illinois mare was bred by artificial insemination with semen from a positive stallion.

Besides the 13 positive horses, 562 other horses have been located that are known to have been exposed to the disease. There are 70 positive or exposed stallions in 14 states and 505 positive or exposed mares in 43 states.

At press time, another 33 exposed horses (19 mares and 14 stallions) were still being traced.

All 575 horses are under quarantine or hold order, and testing and treatment procedures are ongoing.

An exposed horse is defined as one that was bred, naturally or artificially, to a positive horse or one that is epidemiologically linked to a positive horse.

CEM is treated with antibiotics and disinfectants. Positive mares undergo a treatment process and are quarantined at least 21 days. Positive stallions stay under quarantine until they complete treatment and test negative for the disease.