The World Organisation for Animal Health ("OIE") recently issued the following summary of the investigation into the two outbreaks of Contagious Equine Metritis and although a conclusive source has not been identified in the case of the larger (2008) outbreak, considers the investigation closed.
With a lack of a confirmed source, and such a significant number of affected animals, it is unlikely that "CEM Free" status is to be reinstated (which would allow dropping of import restrictions by countries such as Canada) in the near future. The most likely source of the outbreak was identified as a stallion imported from Denmark in late 2000, but that is not absolutely confirmed.
All epidemiologically linked horses have been identified and all testing and treatment protocols have been conducted in accordance with Federal, International, and expert guidance and requirements. Summary of the CEM events:
Kentucky and Wisconsin Event Epidemiology Summary:
•23 stallions and 5 mares were confirmed as positive for Taylorella equigenitalis. All positive horses completed treatment and testing protocols and are negative for T. equigenitalis.
•977 horses potentially exposed to T. equigenitalis were quarantined and had testing protocols implemented. Even though considered low risk for T. equigenitalis infection, 29 horses (3% of horses quarantined) have not completed all testing protocols. All results on these horses have been negative, but they will remain under quarantine until testing is completed in full.
•The 1,005 exposed or positive horses were found in 48 States and included 278 stallions and 727 mares.
•None of the positive horses were definitively identified as the source of the outbreak. However, the results of the investigation of this case, including diagnostic and epidemiologic findings, suggest that a stallion imported from Denmark in late 2000 is the most likely source.
California Event Epidemiology Summary:
•One stallion was confirmed as positive for T. equigenitalis. The positive stallion was identified during routine semen export testing. The positive stallion completed treatment and testing protocols and is negative for T. equigenitalis.
•5 stallions and 18 mares were epidemiologically identified as potentially exposed to T. equigenitalis. All potentially exposed horses were accounted for and testing protocols implemented. All results on these horses have been negative, but they will remain under quarantine until testing is completed in full.
•There is no known relationship between the positive stallion and any horses involved in the Kentucky or Wisconsin outbreaks. Additional analysis indicated the T. equigenitalis isolate from the stallion is not related to other isolates previously found in the United States, and is not related to the Kentucky and Wisconsin outbreaks.
•The results of the investigation of this case, including diagnostic and epidemiologic findings, indicate that the positive Arabian stallion was contaminated with T. equigenitalis prior to his arrival in the United States.
In addition to equine testing for T. equigenitalis related to the CEM event, the United States Department of Agriculture (USDA) conducted a National Testing Project for CEM in 2010. Through the National Testing Project, 292 stallions in 28 States were tested for T. equigenitalis. The stallions tested in the project were not associated with any CEM outbreak, but were considered to otherwise be at highest risk for having T. equigenitalis because they were originally imported from outside the United States or are currently active breeding animals, or both. No positive stallions were detected.
The comprehensive epidemiological investigations of the Contagious Equine Metritis (CEM) events in the United States are closed