Seroprevalence and Molecular Characterization of Coxiella burnetii in Cattle in the Republic of Korea.

This study was conducted to determine the prevalence of Coxiella burnetii in cattle and how that prevalence is influenced by cattle breed and growth type. A total of 491 cattle [cattle breed: 216 dairy cattle and 275 beef cattle; growth type: indoor housed (n = 294) and grazing (n = 197)] were used. The presence of C. burnetii DNA and antibodies was detected from blood and serum samples using polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA), respectively. The overall prevalence of C. burnetii was: 10.8% (95% CI: 8.0-13.5%) using PCR and 8.8% (95% CI: 6.3-11.3%) using ELISA. The prevalence of C. burnetii was significantly higher in beef cattle than in dairy cattle using both PCR (13.5% vs. 7.4%; P = 0.032) and ELISA (14.5% vs. 1.4%; P = 0.000), respectively. Comparison by growth type revealed that C. burnetii infection was significantly higher in grazing cattle than in housed cattle when using both PCR (24.9% vs. 1.4%; P = 0.000) and ELISA (21.3% vs. 0.3%; P = 0.000). Beef cattle were at a significantly higher risk of contracting C. burnetii compared with dairy cattle (odds ratio = 3.20, 95% CI: 1.80-5.67; P = 0.000). The risk of contracting C. burnetii in grazing cattle was increased by 32.57-fold (95% CI: 12.84-82.61; P = 0.000) compared with indoor housed cattle. The phylogenetic analysis based on the IS1111 gene revealed that our sequences grouped with human, tick, goat, and cattle isolates/strains found in several countries. C. burnetii sequences circulating in the Republic of Korea exhibit genetic variations. Thus, grazing is a high risk factor for the prevalence and transmission of C. burnetii.