A-Z Index × Submit A-Z Index × Submit A-Z Index Search Dropdown × Submit Facebook Twitter LinkedIn Syndicate Emerging Infectious Disease journal ISSN: 1080-6059 Disclaimer: Early release articles are not considered as final versions. Any changes will be reflected in the online version in the month the article is officially released.
We isolated Orientia tsutsugamushi bacteria from bat-associated Whartonia prima chiggers collected from Hipposideros turpis bats on Yonaguni Island, Japan. Serial passage, microscopic examination, growth kinetics, and multilocus sequence analysis confirmed bacterial propagation and identity. Our findings highlight an overlooked bat–chigger interface with potential relevance to broader ecologic surveillance of scrub typhus.
Scrub typhus, or tsutsugamushi disease, is a vectorborne zoonosis caused by Orientia tsutsugamushi bacteria. O. tsutsugamushi is transmitted by larval trombiculid mites, or chiggers, and is primarily maintained within chigger populations through transovarial and transstadial transmission ( 1 ). Ecologic studies of scrub typhus have largely focused on rodent-associated Leptotrombidium chiggers, which are the principal vectors in many endemic areas ( 1 ). In Japan, where ≈300–500 scrub typhus cases are reported annually ( 2 ), the ecologic diversity of O. tsutsugamushi in wildlife-associated chiggers remains poorly understood.
Recent molecular detection of O. tsutsugamushi DNA in bats from the China–Myanmar border raised questions about the roles of bats and their ectoparasites in Orientia ecology ( 3 ). Bat-associated chiggers are diverse and widely distributed ( 4 ), but their involvement in Orientia ecology remains limited. We report the isolation and propagation of O. tsutsugamushi from Whartonia prima chiggers collected on Yonaguni Island, Japan, from Hipposideros turpis , a cave-dwelling insectivorous bat endemic to the Yaeyama Islands ( 5 ).
We collected larval chiggers from H. turpis bats on Yonaguni Island in September 2024 and 2025. Bat capture and handling were approved by the Ministry of the Environment, Tokyo, Japan (permission nos. 2402141 and 2502282), and complied with relevant institutional and national guidelines. We examined a total of 80 H. turpis bats, yielding 212 chiggers: 31 in 2024 and 181 in 2025. We identified all chigger mites morphologically as W. prima by using taxonomic descriptions and keys ( 6 , 7 ). We used the chigger mites collected in 2024 for molecular screening. Of the 181 chigger mites we collected in 2025, we used 37 mites for molecular screening, 129 mites for isolation attempts, and 4 mites for scanning electron microscopy; we excluded 11 mites because of poor specimen condition.
Figure 1 . Phylogenetic analyses of Orientia tsutsugamushi detected and isolated from bat-associated Whartonia prima chiggers, Yonaguni Island, Japan. A) Maximum-likelihood tree on the basis of full-length 56-kDa type-specific antigen...
We tested 68 chigger mites individually for O. tsutsugamushi by using real-time PCR targeting the 16S rRNA gene ( 8 ) and nested PCR targeting the 56-kDa type-specific antigen (TSA56) gene ( 9 ). We sequenced amplicons from all nested PCR-positive chigger mite samples, revealing 2 partial TSA56 genotypes. We amplified full-length O. tsutsugamushi TSA56 from 10 mite samples representing both partial genotypes by using previously described primers ( Appendix ) ( 10 ). Of the 68 chigger mites tested, 64 (94%, 95% CI 86%–98%) were positiv…