Long-tailed shrew, Sorex unguiculatus, as a potential reservoir of the spirochetes transmitted by Ixodes ovatus in Hokkaido, Japan

Abstract

To determine the vertebrate reservoirs for the spirochetes transmitted by Ixodes ovatus, the wood mice, Apodemus speciosus ainu, and the longtailed shrews, Sorex unguiculatus, were captured in Furano, Hokkaido during October 1992. Larval and nymphal ticks of I. ovatus were more abundant on the shrews than on the mice. The spirochetes were isolated repeatedly from earlobe tissues of both the mice and the shrews. The spirochetal isolates derived from the shrews contained the 30kDa homogeneous OspA protein, and were similar to the control strain of I. ovatus adult origin in their SDS-PAGE protein profile. In contrast, the isolates from the mice were polymorphic in their OspA proteins, and distinguishable from the shrew-derived isolates. All the spirochetal isolates from I. ovatus larvae feeding on the shrews were also identical with the control strain of I. ovatus adult origin. These data strongly suggest that S. unguiculatus is a reservoir for the spirochetes transmitted by I. ovatus. Similar enzootic cycles involving insectivores should be sought in the mainland of Honshu, Japan.