Rickettsia tsutsugamushi in chiggers (Acari: Trombiculidae) associated with rodents in central Thailand.

Chiggers were collected from rodents trapped at two military bases located 10 km apart in central Thailand. One site was swampy and nearly treeless and the other site was well-drained and partially wooded. Although 13 species of chiggers were collected, only three species were found to be positive for Rickettsia tsutsugamushi (Hayashi) Ogata using a direct fluorescent antibody test: Blankaartia acuscutellaris Walch (7.3% infected), Leptotrombidium delinese Walch (3.1% infected), and an undescribed species of Ascoschoengastia near A. indica Hirst (1.2% infected). This was the first record of R. tsutsugamushi in B. acuscutellaris. The Ascoschoengastia species occurred with equal frequency at the two study sites, L. deliense occurred more frequently at the well-drained site, and B. acuscutellaris occurred more frequently at the swampy site. Results suggest that there are important foci of scrub typhus in central Thailand and that B. acuscutellaris may be a vector in this area.