In February 2013, the USDA's National Veterinary Services Laboratories (NVSL) confirmed that a Lusitano mare in south-central California was positive for Taylorella equigenitalis, the bacterium that causes contagious equine metritis (CEM). The NVSL also determined that the strain of the bacterium does not match any T. equigenitalis strains ever found in the United States, indicating this case is not related to any previous U.S. cases of CEM.
A thorough epidemiologic and diagnostic investigation of these cases is underway. The positive Lusitano mare was imported as a foal from a country not known to be affected by CEM. All her recent breeding has been to a Lusitano stallion in California. That stallion was imported as an adult from the same country as the positive mare, and he is one of the two exposed stallions found positive with a strain of T. equigenitalis that matches the strain from the positive mare. The second positive stallion is a domestic Lipizzan that had semen collected at the same facility as the positive Lusitano stallion in 2012. The second positive mare is a domestic cross-bred Andalusian. She had been bred by artificial insemination to the positive Lusitano and is now pregnant.
In addition to the positive horses, a total of 13 horses are currently known to have been exposed to a positive horse. Nine exposed horses, including seven stallions and one gelding (exposed as a stallion) in California and one stallion in another State, have been tested with negative results, treated, and released from quarantine. Each exposed horse identified in the investigation will complete a testing and treatment protocol to determine its CEM status.
In July 2011, the USDA's National Veterinary Services Laboratories (NVSL) confirmed that an Arabian stallion on a central Arizona premises was positive for Taylorella equigenitalis, the bacterium that causes contagious equine metritis (CEM). The NVSL has also determined that the strain of the bacterium does not match any T. equigenitalis strains recently found in the United States, indicating this case is not related to the California CEM case in May 2010, the multi-State CEM outbreak detected in late 2008, or imported stallions found positive in 2006.
The positive stallion was born in Arizona in 2007. He was tested for CEM to meet requirements for international shipment of his semen. After testing positive, the stallion received antibiotic treatment for T. equigenitalis and was re-tested with negative results.
A thorough epidemiologic and diagnostic investigation of the case was conducted. Information from the investigation indicates that 17 other stallions in 2 States, and 13 mares in 6 States, were exposed to the positive stallion. Although one exposed mare died of unrelated causes before completing testing, all other exposed stallions and mares completed a testing protocol to determine their CEM status. All 29 of those exposed horses (17 stallions, 12 mares) were found negative for T. equigenitalis.
In May 2010, the USDA's National Veterinary Services Laboratories (NVSL) confirmed that an Arabian stallion on a southern California premises was positive for Taylorella equigenitalis, the bacterium that causes contagious equine metritis (CEM). A thorough epidemiologic and diagnostic investigation was carried out to determine the origin of the CEM bacterium. Final analysis of all the epidemiologic and diagnostic findings from the investigation indicated that the positive Arabian stallion was contaminated with T. equigenitalis prior to his arrival in the United States and that no further spread of the bacterium occurred after he arrived. The positive imported stallion successfully completed antibiotic treatment and was confirmed to be free of T. equigenitalis.
The positive stallion was imported into the United States in March 2010 from a country not known to be affected by CEM. The NVSL determined that the strain of the isolated bacterium did not match any T. equigenitalis strains previously found in the United States, indicating this case was not related to the multi-State CEM outbreak detected in late 2008.
A total of 23 horses exposed to the positive imported stallion were located and tested for T. equigenitalis. Five exposed stallions were located in California, and 18 exposed mares were located in a total of 8 States. All of the exposed horses, completed an appropriate testing protocol and all were found negative for T. equigenitalis.
In December 2008, a Quarter Horse stallion on a central Kentucky premises was confirmed by the USDA’s National Veterinary Services Laboratories (NVSL) as positive for Taylorella equigenitalis, the bacterium that causes contagious equine metritis (CEM). A thorough epidemiologic and diagnostic investigation was carried out to determine the origin of the CEM bacterium. Final analysis of all the epidemiologic and diagnostic findings from the investigation indicated that a stallion imported from Denmark in late 2000 was the likely source of the outbreak. The source stallion and 27 other horses found positive in the outbreak were all successfully treated with antibiotics and confirmed as free of T. equigenitalis.
The NVSL determined that the strain of T. equigenitalis found in this outbreak did not match any strains found in other U.S. outbreaks or cases of CEM, indicating that this outbreak was not associated with cases found in three imported stallions in 2006. Further investigation and testing of exposed horses found a total of 5 mares and 23 stallions, including one that is now a gelding, positive for T. equigenitalis. The 23 positive stallions were found in 7 States: 1 in Georgia, 3 in Illinois, 3 in Indiana, 1 in Iowa, 4 in Kentucky, 1 in Texas, and 10 in Wisconsin. The five positive mares were found in three States: two in California, two in Illinois, and one in Wisconsin.
In addition to the 28 positive horses, another 977 horses were exposed to T. equigenitalis in the outbreak. The 1,005 horses were found in 48 States. A total of 278 exposed or positive stallions were found in 31 States, and 727 exposed or positive mares were found in 46 States. Hawaii and Rhode Island are the only States in which an exposed or positive horse was not found.
Overall, 971 (96.6 percent) of the 1,005 horses are now known to be free of T. equigenitalis. Six of the eight States that had a positive horse (California, Georgia, Indiana, Iowa, Kentucky, and Texas), completed the testing and treatment of all known positive and exposed horses. The remaining two States with positive horses - Illinois and Wisconsin - completed treatment and negative re-testing of all positive horses, but one or more exposed horses remain under quarantine in each of those States because they completed only one set of negative cultures.
Of the 278 stallions, 261 (93.9 percent) completed an appropriate testing and treatment protocol and were found negative for T. equigenitalis. Another 14 exposed stallions (5.0 percent) had one set of negative cultures but will remain under quarantine indefinitely unless testing and treatment are completed in full. Three exposed stallions (1.1 percent) died, one after testing negative on one set of cultures and two prior to any testing .
Of the 727 mares, 710 (97.7 percent) completed testing and treatment and are negative for T. equigenitalis. Eight exposed mares (1.1 percent) did not complete their testing and will remain under quarantine indefinitely unless testing and treatment are completed in full. The remaining nine mares (1.2 percent) were not tested, either because it was determined that they were never actually exposed or because of the mare's death prior to testing.
The investigation of this outbreak determined that all four of the positive Kentucky stallions were on the central Kentucky premises during the 2008 breeding season. The Texas and Indiana stallions also spent time on the Kentucky premises during 2008. The positive Wisconsin stallions were not in Kentucky, but four of them were co-located during at least one breeding season in Wisconsin with a positive stallion that was on the Kentucky premises in 2008. The fifth, sixth, seventh, eighth, ninth, and tenth Wisconsin stallions all spent time at a breeding facility used by the fourth positive Wisconsin stallion, by the three positive Illinois stallions, and by the Iowa stallion (now a gelding). The positive Georgia stallion was co-located with three positive Wisconsin stallions in 2008.
The positive Wisconsin mare was bred by the second positive stallion in Wisconsin. Each of the positive mares in Illinois and in California was bred by artificial insemination (AI) in 2008 using semen from a positive stallion. Both California mares were exposed by AI to the first positive stallion in Wisconsin and the first Illinois mare was exposed to a positive stallion now in Indiana. The second positive mare in Illinois was exposed by AI in 2008 to the second positive Illinois stallion.
Last Modified: May 21, 2013