Detection of Coxiella burnetii in raw milk samples collected from dairy farms in Mazandaran province, north of Iran

Query fever is an important zoonotic disease caused by the obligate intracellular microorganism of Coxiella burnetii. Moreover, the present study aimed to determine the prevalence of C. burnetii in bulk milk samples from dairy bovine herds using a nested polymerase chain reaction assay. During four seasons, a total of 100 samples of bulk milk from traditional, semi-industrial, and industrial dairy bovine herds located in six cities of Mazandaran province, northern Iran from May 2019 to February 2020 were collected. The samples were subjected to detect C. burnetii using a nested-PCR assay. Twenty - seven out of 100 bulk milk samples (27%, 95% CI: 18.3-35), 7% were infected with C. burnetii. The prevalence was 54.3% (19 samples) in traditional dairy herds and 12.3 % (8 samples) in semi-industrial industrial dairy herds. Furthermore, our results revealed that the chance of milk being infected with C. burnetii bacteria in traditional milk is 8.5 times higher than the milk of semi-industrial and industrial dairy herds. Based on the obtained results of the current study, the highest and lowest prevalence of C. burnetii were seen in Ghaemshar (66.7%) and Babol (0%), respectively (p<0.05). Spring season (37%) had the highest contamination of C. burnetii in bulk milk samples. According to the findings of this study, the clinically healthy dairy cows are important sources of C. burnetii infection in this area, amplified by the traditional herds of these animals. Because these animals can transmit the infection to humans, this common zoonotic bacterium can be a potential health problem in Mazandaran province, Northern Iran.