Before Christmas it was reported that a 16-year-old Quarter Horse stallion at an AI centre in Kentucky tested positive for Taylorella equigenitalis, the causal agent of contagious equine metritis (CEM), during the process of certifying semen for export. More stallions at the same studfarm were then tested positive. As semen from affected stallions had been shipped widely, Quarter Horse and Paint stallions and mares at studfarms in other states and in Canada came under investigation.
A report by the USDA’s Animal and Plant Health Inspection Service (APHIS) shows that a total of eight stallions have now been confirmed as positive for CEM by USDA’s National Veterinary Services Laboratories. Four of the infected stallions are located in Kentucky, three are in Indiana, and one is in Wisconsin.
In addition to the 8 positive stallions, the locations of 326 ‘exposed’ horses have also been confirmed. The total of 334 horses includes 43 stallions and 291 mares located in a total of 39 States. There are 43 additional exposed mares still actively being traced. An ‘exposed’ horse is one that was bred to a CEM-positive horse, either naturally or via artificial insemination, or one that is otherwise epidemiologically linked to a CEM-positive horse, as determined by State and Federal animal health officials. All CEM-positive horses, and all exposed horses that have been located, are currently under quarantine or hold order. Testing and treatment protocols are being put into action for all located horses.
In the UK, the Horserace Betting Levy Board’s voluntary Code of Practice, recently published in its 2009 format, covers prevention of CEM. Clients have asked us if mares from North America should be considered ‘high risk’. While the Code of Practice Committee have not yet ruled on this, we advise that this would be a wise precaution until all the ramifications, if any, for the North American 2009 Thoroughbred breeding season become clear. This means two negative clitoral fossa and sinus swabs and one negative endometrial swab (collected during oestrus) microaerophilic cultures for Taylorella equigenitalis before presentation to the stallion. It also means missing the ‘foal heat’. We believe that the time and the extra costs involved are prices worth paying to help maintain our current freedom from this important equine venereal disease.