Status of Taylorella equigenitalis Infection in Thoroughbred Horses in the Republic of Korea and the Molecular Characterization of the Korean Taylorella equigenitalis Isolates

Contagious equine metritis is a highly transmissible venereal disease of horses caused by the bacterium, Taylorella equigenitalis. After the first identification of T. equigenitalis in Korea in 2015, targeted surveillance of Thoroughbreds was conducted using real-time polymerase chain reaction. Initially, the prevalence of T. equigenitalis in the Thoroughbred population tested was 13.5% (71/526). All positive animals were placed under quarantine and treated according to previously described protocols (Jeoung et al., J Equine Vet Sci, 2016; 47:42–6). After the initial outbreak identification, annual national surveillance for T. equigenitalis was conducted from 2015 to 2017, and by 2017, prevalence was reduced to 1.0% (22/2,171). Most positive cases were located in Jeju province, the major horse-rearing region in Korea. A total of 12 T. equigenitalis strains were isolated during the surveillance period, and multilocus sequence typing (MLST) and eBURST analysis were applied to determine epidemiological characteristics. All Korean strains showed a unique MLST allelic profile (1-2-1-2-2-2-1; gltA-gyrB-fh-shmt-tyrB-adk in order) and were classified as sequence type 55. In addition, they showed little relationship with T. equigenitalis strains isolated from other countries. Considering the unique biological and genetic characteristics of the Korean isolates, effective quarantine measures and continued surveillance will be required to eradicate the disease and prevent incursions of additional T. equigenitalis strains into Korea.