Evaluation of qPCR and phase I and II antibodies for detection of Coxiella burnetii infection in cattle.

Diagnosis of Q fever in cattle is not easy due to the need to test the samples by both serological and molecular methods. Aim of this study was to evaluate qPCR, and phase I and II antibodies for detection of C. burnetii infection in cattle. A total of 187 bovine blood and vaginal swabs, and 97 milk samples, were tested. Limitations of serological tests were that the available indirect enzyme linked immunosorbent assay (iELISA) could lose positive results if antibody titres were low; or phase II antibodies were present. The highest level of correlation between iELISA and complement fixation test (CFT) was noted with the antigen specific phase I antibodies. Neither the mode of shedding nor its intensity correlated with phase I and II antibodies, but positive results in CFT mixed-phase and shedding in vaginal mucous did correlate, and showed the highest correlation. Antigenic diversity, and variability could be crucial in laboratory diagnosis of Q fever.