Identification and characterization of Chlamydia abortus isolates from yaks in Qinghai, China

Recently, the yak population has exhibited reproductive disorders, which are considered to be associated with Chlamydia abortus (C. abortus) in Qinghai, China. In this study, a total of 9 aborted fetuses (each from a different herd) and 126 vaginal swab samples from the 9 herds were collected and analyzed. C. abortus DNA was detected from all of the 9 aborted fetuses and 30 of the 126 vaginal swab samples (23.81%) from yak cows in the selected herds. Four C. abortus strains were isolated from embryonated egg yolk sacs inoculated with foetal organ suspensions. The isolated C. abortus strains were further identified, which showed identical restriction profiles with the C. abortus reference strain using AluI restriction enzyme in the RFLP test. Moreover, the isolated C. abortus strains and C. abortus-positive vaginal swab samples were genotyped by multiple loci variable number tandem repeat analysis and all belonged to the genotype 2 group. These findings suggested that C. abortus played a substantial role in yak abortion in Qinghai, China.