CEM probe continues, affects 563 horses in 46 states

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 563 horses in 46 states.

Since the first confirmed case, in a Quarter Horse stallion in Kentucky on Dec. 15, a total of 11 stallions and one mare 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, and the one positive mare is in Wisconsin, according to USDA's Animal and Plant Health Inspection Service (APHIS).

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.

Besides the 12 positive horses, 551 other horses are known to have been exposed to the disease, and another 33 exposed horses (31 mares and two stallions) are being traced.

All 563 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.