CEM probe continues, involves 711 horses in 46 states

National Report

-- An outbreak of contagious equine metritis (CEM) that began more than three months ago now involves 711 horses in 46 states, as state and federal veterinary investigators continue to look for the source.

A total of 13 stallions and three mares have been confirmed positive for T. equigenitalis, the causative bacterium for the sexually transmitted disease that can cause abortions and infertility.

The positive stallions are in five states - one in Georgia, three in Indiana, four in Kentucky, one in Texas and four in Wisconsin. The positive mares are in California, Illinois and Wisconsin, according to the USDA's Animal and Plant Health Inspection Service (APHIS), which is overseeing the investigation.

During the 2008 breeding season, all four Kentucky stallions were on the central Kentucky premises where the first positive case was reported in a Quarter Horse stallion last Dec. 15.

The Texas and Indiana stallions also spent time on the Kentucky premises in 2008. The Wisconsin stallions were co-located during at least one Wisconsin breeding season with a positive stallion that was on the Kentucky site in 2008, and the positive Georgia stallion was co-located with three positive stallions in Wisconsin in 2008.

The postive Wisconsin mare was bred by a positive stallion in Wisconsin, while the positive mares in Illinois and California were bred by artificial insemination with semen from two different positive stallions, APHIS says.

Besides the 16 positive horses, locations were confirmed for 695 other horses exposed to the disease - 112 stallions and 599 mares. Six exposed mares and four exposed stallions are still being traced.

Of the 112 exposed stallions, 34 have completed testing and treatment protocols and determined to be negative, and 270 exposed mares have completed treatment and are now negative, APHIS reports.

In New York, where one stallion and nine mares were reported exposed, the New York State Veterinary Medical Society is sponsoring two free continuing-education sessions on CEM for about 50 accredited New York veterinarians at Cornell's College of Veterinary Medicine. Both sessions are full, but other interested New York DVMs can request a copy of the manual by contacting Teresa Steigerwalt at Cornell's Animal Health Diagnostic Center at (607) 253-3931 or ts284@cornell.edu.

The transmission rate for CEM is high and occurs through mating, contaminated instruments and through semen collected for artificial insemination.