Prevalence of Lyme borrelia in ticks, especially Ixodes persulcatus (Acari: Ixodidae), in central and western Japan.

Prevalence of Lyme Borrelia in unfed ticks was surveyed in central and western Japan during spring from 1991 to 1993. The tick fauna was diverse; ticks obtained consisted of four genera and more than 12 identified species, and both southern and northern species coexist with altitudinal separation. Midguts of ticks were cultured in BSK medium for spirochetal isolation. Borrelia-positive rates for adults of both a common species, Ixodes ovatus Neumann, and a northern species, Ixodes persulcatus Schulze, in the extreme western part of the Japanese central mountainous zone (Fukui and Gifu prefectures) were 18.1 and 12.9%, respectively. A Borrelia-positive nymph of Haemaphysalis flava Neumann also was found for the first time in Japan. In contrast, I. persulcatus in southwestern Japan was localized in mountains with elevations over 800 m and was determined negative for Borrelia, whereas I. ovatus was highly positive (28.8%). These Borrelia isolates were diverse in typing of protein profiles. Our results reveal that I. persulcatus-borne Borrelia derived from northern Japan is kept within the limits of the western extremity of the central mountainous zone.