Competence of a migratory bird, red-bellied thrush (Turdus chrysolaus), as an avian reservoir for the Lyme disease spirochetes in Japan

To evaluate the competence of migratory birds as reservoirs for the Lyme disease spirochetes, we examined two species of migrants, Red-bellied thrush (Turdus chrysolaus) and Black-faced bunting (Emberiza spodocephala) in Nemuro, the northern part of Japan. Spirochetes were found in four individual birds out of 11 T. chrysolaus, three isolates were detected from the skins and the other one was obtained from the liver. No spirochete was found to be infected in 20 E. spodocephala. As far as we know, this is the first record of direct detection of the spirochetes from migratory birds in Japan. The spirochetes were also isolated from immature ixodid ticks, Ixodes persulcatus, fed on those species of birds. The spirochetes were transmitted trans stadially to the next stage, when infected ticks molted. All of the isolates from birds and ticks were identified as Borrelia garinii by our ribotyping and flagellin gene sequence analyses. Our results strongly suggest that the migratory birds are reservoirs in the transmission of the Lyme disease spirochetes in Japan.