Molecular Epidemiology of an Orientia tsutsugamushi Gene Encoding a 56-kDa Type-Specific Antigen in Chiggers, Small Mammals, and Patients from the Southwest Region of Korea

A phylogenetic analysis of was performed to elucidate its antigenic diversity in chiggers, small mammals, and patients. Between September 2014 and December 2016, a total of 3,816 chiggers were identified within nine species of four genera in the southwest region of Korea: (49.9%; 1,907/3,816), (21.1%; 804/3,816), (12.4%; 474/3,816), (7.2%; 273/3,816), (6.7%; 256/3,816), (1.3%; 50/3,816), (0.8%; 32/3,816), (0.5%; 18/3,816), and (> 0.1%; 2/3,816). Twelve chiggers (11 and one ) tested positive for by polymerase chain reaction and, except for 1 chigger (KY266830), were part of the Boryong strain cluster. Of the 413 small mammals that were analyzed for , was the most common rodent species (89.5%; 370/413), followed by (6.8%; 28/413) and (3.6%; 15/413). The sequence identity of an sample obtained from the sample population belonged to the Saitama strain cluster. Furthermore, a phylogenetic analysis in 125 patients revealed four clusters (Boryong cluster: 82.4% [103/125], Karp: 13.6% [17/125], Kawasaki: 3.2% [4/125], and Saitama: 0.8% [1/125]). This study clarified the phylogenetic relationship for in chiggers, small mammals, and patients. The Boryong strain was the most common strain in chiggers and patients. In addition, various strains were identified, except for the Boryong strain, in the southwest region of Korea. Overall, the data presented here will be helpful for the establishment of prevention strategies for scrub typhus.