Neglected zoonotic agents in cattle abortion: molecular and serological screening of difficult to grow bacteria

Coxiella burnetii, Chlamydia abortus and Leptospira spp., are three agents that may lead to bovine abortion. The importance of these difficult to grow zoonotic bacterial pathogens lies in significant economic loss in animal production and the public health risk, at least in endemic countries. Routine bacteriological diagnostics of abortion in cattle in Switzerland is regulated by law including screening by serology and staining. However, only few infectious agents are examined using molecular approaches due to the high costs associated with extended analyses. In the present work, we used both serological and molecular methods to assess the possible role of these pathogens in bovine abortion. From 249 studied bovine abortion events, 242 placenta samples, 57 fetal abomasal content and 182 sera were taken from mother cows. The seroprevalence was 15.93%, 38.46% and 21.43% for C. burnetii (ELISA), C. abortus (ELISA) and pathogenic Leptospira spp. (microscopic agglutination test), respectively. Using specific real time PCR, the prevalence of C. burnetii, Chlamydiales and pathogenic Leptospira spp., were of 12.15%, 16.87% and 8.24%, respectively. After direct sequencing of Chlamydiales positive samples, we identified C. abortus in 8.84% of the cases and probable infection with Chlamydia-related bacteria in 5.22% of the cases. Altogether, routine abortion diagnostics did not detect a possible bacterial agent in 96 cases. Extending the spectrum of analysis could assign at least one possible abortive agent in 39 more cases. In conclusion, diagnostic approaches enabling the detection of C. burnetii, C. abortus and Leptospira spp., should be used more commonly due to their zoonotic potential.