[Studies on tsutsugamushi disease in Gifu prefecture. 4. Survey results in Ena and Takayama City, and the summary of the studies in the prefecture].

Investigations of trombiculid mites and Rickettsia tsutsugamushi in wild rodents were made in Ena (Nov. 1988) and Takayama (May 1989) City. In the former area where no patient has been reported so far, Leptotrombidium pallidum (63.9%) was most predominant and no L. scutellare was found. A Karp-related rickettsia (11.1%) was isolated from wild rodents and 30% of them had antibody to R. tsutsugamushi (anti-Karp was prominent). The latter area where patients were reported in spring as well as in autumn, L. pallidum (22.4%) was one of the dominant species in spring. Karp-related strains were isolated from 37.5% of wild rodents. And the antibody possession rate was 50.0%. These data reconfirmed our hypothesis that the majority of patients in autumn were infected by L. scutellare and a part by L. pallidum. In spring in Takayama area, the vector was L. pallidum which possessed Karp-related strain(s).