Prevalence and Molecular Characterization of Coxiella burnetii in Cattle, Goats, and Horses in the Republic of Korea

Coxiella burnetii is an obligate intracellular zoonotic bacterium with a global distribution. This study was conducted to investigate the prevalence of C. burnetii in different animals and to assess the potential role of these species as reservoirs of infection and transmission to humans. A total of 592 blood samples (105 beef cattle, 61 dairy cattle, 110 Korean native goats, 83 Boer goats, and 233 horses) were collected in the Republic of Korea (ROK). The C. burnetii DNA was detected from blood samples using the transposon-like repetitive region (IS1111) by PCR method. The results showed that 22.7% of the Korean-native goats, 16.4% of the dairy cattle, 15.2% of the beef cattle, 6.0% of the Boer goats, and 5.2% of the horses were positive for C. burnetii. Significant differences were found between the animal species. The univariable binary logistic regression analysis revealed that the risk of contracting C. burnetii was significantly high by 5.4-fold in Korean-native goats (95% confidence interval [CI]: 2.60%-11.27%, p = 0.000), 3.6-fold in dairy cattle (95% CI: 1.48%-8.82%, p = 0.005), and 3.3-fold in beef cattle (95% CI: 1.51%-7.28%, p = 0.003) compared with horses. A phylogenetic tree based on the IS1111 gene revealed that our sequences had 92.2%-99.9% similarity and were clustered with those detected in humans, cattle, goats, dogs, rodents, and ticks. C. burnetii circulating in the ROK exhibits genetic variation. To the best of our knowledge, this is the first study to identify C. burnetii DNA in a horse in the ROK. These results suggest that cattle, goats, and horses can be potential reservoirs for C. burnetii and play an important role in the transmission of infection. Further studies should assess the pathogenicity of C. burnetii circulating in the ROK.