1ST ISOLATION OF A RICKETTSIA CLOSELY-RELATED TO JAPANESE SPOTTED-FEVER PATHOGEN FROM A TICK IN JAPAN

In May 1993, we collected unfed ticks in Anan, Tokushima Prefecture, S hikoku District, Japan, a highly endemic area of Japanese spotted feve r (JSF). We isolated JSF rickettsiae from these ticks by inoculating t ick-emulsions into L-929 cells. Of the four genera and seven species o f ticks examined, only one larva of Dermacentor taiwanensis Sugimoto y ielded a rickettsial isolate. The isolate (DT-1 strain) was found to b elong to the serotype common to the causative agent of JSF. This was b ased on its specific reactivity to mouse antisera and to a monoclonal antibody to JSF rickettsiae from the Shikoku District. This is the fir st tick-borne spotted fever group of rickettsia isolated in Japan. How ever, all stages of D. taiwanensis infrequently parasitize humans. Som e ticks in the genus Haemaphysalis commonly infest humans and are freq uently found to be rickettsia-positive in the hemolymph test when usin g the monoclonal antibody mentioned above. Therefore, the vectors of J SF rickettsiae to humans may be a complex of tick species.