By Erin Ryder, TheHorse.com News Editor
The ongoing investigation into venereal disease contagious equine metritis has now located 21 stallions--one of which is now a gelding--positive for the causative organism Taylorella equigenitalis.
According to the United States Department of Agriculture, the 21 positive stallions were found in seven states: one in Georgia, three in Illinois, three in Indiana, one in Iowa, four in Kentucky, one in Texas, and eight in Wisconsin.
Overall, the investigation now includes 939 exposed or positive horses. The origin of the outbreak remains unknown.
According to reports from the World Organization for Animal Health and the USDA, the group of positive stallions includes the following breeds: Thoroughbred, Appaloosa, Arabian, Dutch Warmblood, Fjord, Friesian, Hackney, Paint, Quarter Horse, and Saddlebred.
Per the OIE report, the Thoroughbred stallion has had very limited use as a breeding stallion and all through semen collection and artificial insemination, with no live-cover breeding reported.
The investigation began in mid-December 2008, when a Quarter Horse stallion on a Kentucky farm tested positive during routine screening for international semen shipment.
According to the USDA's Animal and Plant Health Inspection Service, as of June 2 the positive horses include 21 stallions and five mares. In addition to those horses, they have confirmed the locations of 913 horses exposed to Taylorella equigenitalis. The 939 horses are located in 48 states (only Hawaii and Rhode Island do not have at least one exposed or positive horse). There are 272 exposed or positive stallions in 29 states and 667 exposed or positive mares in 46 states.
An exposed horse is one that was bred to a positive horse, either naturally or via artificial insemination, or one that is otherwise epidemiologically linked to a positive horse, as determined by animal health officials.
All positive horses, and all exposed horses that have been located, are currently under quarantine or hold order.
Of the 272 stallions involved, a total of 85 have completed their entire testing and treatment protocol and are negative for T. equigenitalis. Of the 667 mares, 466 have completed testing and treatment.