Susceptibility of Ixodes persulcatus and I. ovatus (Acari: Ixodidae) to Lyme disease spirochetes isolated from humans in Japan.

Susceptibility of Ixodes persulcatus Schulze and Ixodes ovatus Neumann to Lyme disease spirochetes isolated from humans was studied under laboratory conditions. Six isolates (JEM3, JEM4, JEM5, JEM6, JEM7, and JEM8) from patients in Japan were used for the study. Mongolian jirds were inoculated intraperitoneally with each of the isolates. Larval ticks of either I. persulcatus or I. ovatus were allowed to feed on the jirds and reared for development into nymphs. In all human isolates examined, the replete larvae of both tick species ingested spirochetes. However, retention of the spirochetal infections through the molting process was observed only in I. persulcatus. These data clearly indicate that I. persulcatus is susceptible to the spirochetes that are pathogenic to humans. The principal vector of Lyme disease to humans in Japan is considered to be I. persulcatus.