DISTRIBUTION OF BORRELIA SPECIES ASSOCIATED WITH LYME-DISEASE IN THE SUB-ALPINE FORESTS OF NAGANO PREFECTURE, JAPAN

We surveyed the natural distribution of Borrelia species associated wi th Lyme disease in the subalpine forests of Nagano prefecture, Japan, during 1993-94. Tick-derived isolates (n = 112) from Ixodes persulcatu s and rodent-derived isolates (n = 55) from Apodemus argenteus, Apodem us speciosus, Eothenomys andersoni, Eothenomys smithii, and Microtus m ontebelli were classified by rRNA gene restriction fragment length pol ymorphism analysis (RFLP ribotyping). Ribotype group IV (an intraspeci fic variant of Borrelia garinii) was predominant among the tick isolat es. It was also isolated repeatedly from the rodents. Ribotype group I II (Borrelia afzelii) was detected in low frequencies among the tick a nd rodent isolates. The data suggest that humans are likely to be expo sed to the group IV when they are bitten by I. persulcatus ticks.