CEM probe passes 6-month mark

National Report

-- Federal and state veterinary investigators continue to look for the source of an outbreak of contagious equine metritis (CEM) that began more than six months ago in Kentucky and now involves horses in 48 states.

"The epidemiologic investigation continues to pursue all available information relative to determining the origin of the outbreak, but no conclusions can yet be drawn," according to the latest update on the USDA's Animal and Plant Health Inspection Service (APHIS) Web site. Some state investigators have said the source may never be known.

So far, 21 stallions and five mares have been confirmed positive for T. equigenitalis, the causative organism for the disease. Eight of the stallions were found in Wisconsin, four in Kentucky, three each in Indiana and Illinois and one each in Georgia, Iowa and Texas. Two positive mares were identified in California, two in Illinois and one in Wisconsin.

In addition to the positive horses, 952 others are known to have been exposed. The total 978 are in 48 states, with only Hawaii and Rhode Island having no positive or exposed horses.

Clinical signs of CEM in mares include a mucopurulent vaginal discharge, along with abortion and infertility. Stallions typically show no clinical signs, but both stallions and mares can become chronic carriers, and the transmission rate is high. The disease can be passed naturally in mating and through contaminated instruments used in artificial insemination.

Of 270 exposed or positive stallions, 110 have now completed the entire testing and treatment protocol and determined to be negative, investigators say. Of 708 mares, 572 have completed testing and are now negative.