CEM investigation involves all but 12 states

National report

-- Four confirmed cases of contagious equine metritis (CEM) in Kentucky last month triggered an investigation that so far involves all but 12 states, according to the USDA's Animal and Plant Health inspection Service (APHIS).

CEM is a highly contagious venereal disease, restricted to the reproduction tract of mares, that usually causes temporary infertility. It is transmitted either during breeding or through artificial insemination.

The first case was confirmed in a Quarter Horse stallion on a central Kentucky premises on Dec. 15 during routine testing before a semen shipment to Canada. Three more stallions on that property soon after tested positive, as did three Indiana stallions that spent time on the Kentucky property in 2008. There are now six other exposed stallions and 22 exposed mares in Kentucky, for a total of 32 in that state that are either CEM positive or exposed, APHIS reports. Testing was done at USDA's National Veterinary Services Laboratories.

An exposed horse is one that was on the index premises in Kentucky or one that was bred to a CEM-positive horse, either naturally or via artificial insemination.

Outside Kentucky, 92 exposed horses plus three positive stallions have been confirmed. That total includes 12 stallions and 83 mares in 28 different states. All the positive horses and all exposed horses that have been located are under quarantine or hold order, and testing and treatment protocols are being implemented, APHIS says.

At least 250 additional horses are being traced, with owners located in 27 states, leaving only 12 states with no involvement so far, APHIS says.

Veterinarians from the Texas Animal Health Commission (TAHC) contacted owners of 14 mares and a stallion with links to infected horses, and testing of those 15 horses is going on this week. Texas currently has no known CEM infection.

CEM is treated with disinfectants and antibiotics. Infected mares are quarantined at least 21 days. Stallions must remain quarantined until a treatment protocol is completed and they test negative.

The disease was first detected in the United States in 1978 and again in 1979, and was eradicated both times.