Coxiella burnetii occurrence in dairy herds in Gabrovo Region, Bulgaria, evaluated by serological and molecular analyses of bulk-tank milk samples

Abstract

This study investigated the occurrence of Coxiella burnetii in dairy cattle, goat herds and sheep flocks in the Gabrovo Region, central Bulgaria, to identify the potential sources of Coxiella burnetii infection diagnosed in veterinarians and farm workers in this region. To detect infection on livestock farms, we tested bulk-tank milk (BTM) for the presence of antibodies and/or the Coxiella burnetiid genome using ELISA and PCR, respectively. A total of 81 herds were tested, including 23 dairy cattle herds, 43 sheep herds, 9 goat flocks, and 6 mixed flocks (sheep and goats). By ELISA, antibodies against Coxiella burnetii were detected in 30.4% of the BTM tested samples from cattle farms, 60.4% of the sheep farms, and 11.1% of the goat BTM samples. The results were inconclusive in 6.98% of the tested sheep milk samples and 11.1% of the goat milk samples. There was a statistically significant correlation between the herd size and the ELISA S/P % values on the dairy cattle farms. Excretion of the pathogen in milk was detected by PCR in 9 out of 67 BTM samples, including 5 out of 19 cattle BTM samples, 3 out of 39 sheep BTM samples and 1 out of 5 goat BTM ones. The results indicate that C. burnetii infection is widely prevalent in the region, which calls for adequate control and prophylactic measures to reduce the health risks from the transmission of this zoonosis to humans.