First serologic survey of Q fever in free-range yaks in China.

The objective of the present investigation was to determine the seroprevalence of Coxiella burnetii infection in free-range yaks in China. A total of 552 serum samples were collected from yaks in Gansu province, northwest China between April 2013 and January 2014, and antibodies against C. burnetii were evaluated using enzyme-linked immunosorbent assay (ELISA). Overall, 13.59% (75/552, 95% CI: 10.73-16.45) of the examined animals were positive for C. burnetii antibodies. There was no significant difference in C. burnetii seroprevalence between female yaks (13.78%, 95% CI: 10.36-17.19) and male yaks (13.13%, 95% CI: 7.89-18.36) (P>0.05). Coxiella burnetii seroprevalence in yaks in different age groups ranged from 10.88% to 15.26%, but the difference was not statistically significant (P>0.05). Coxiella burnetii seroprevalence in yaks sampled in different seasons ranged from 12.06% (autumn) to 18.33% (summer), but the difference was not statistically significant (P>0.05). This is the first report of C. burnetii seroprevalence in free-range yaks in China, indicating the need for measures to be taken to control C. burnetii infection in free-range yaks in China.