CEM update: 820 positive and exposed horses in 48 states

National Report

-- The latest update on the nationwide outbreak of contagious equine metritis (CEM) that began about five months ago shows 18 stallions in six states and five mares in three states so far confirmed CEM-positive by the USDA's National Veterinary Services Laboratories.

Besides the positive horses, the USDA's Animal and Plant Health Inspection Service (APHIS) says locations have been confirmed for 797 other horses exposed to T. equigenitalis, the bacterium that causes the sexually transmitted disease that can cause sterility and abortions if untreated.

The 820 total positive and exposed horses are in 48 states, with 171 exposed or positive stallions in 27 states and 649 exposed or positive mares in 45 states.

Federal and state veterinary investigators continue to look for the original source of the outbreak, first reported on a central Kentucky premises in December 2008, but say no conclusions can yet be drawn.

Of the 171 stallions, 41 have completed the testing and treatment regimen and found negative, while 365 of the mares have completed treatment.

An exposed horse is one that was bred to a positive horse, either naturally or through artificial insemination, or one that is epidemiologically linked to a positive horse by inspectors.