In order to explore the involvement of terrestrial birds in the ecology of
Lyme disease spirochetes, we determined the presence of Borrelia burgdorferi s. I. DNA in tick larvae feeding on the hosts. Birds were caught at several study sites along the Rhine valley in SW Germany between August 1999 and March 2001. A total of 987 Ixodes ricinus larvae were collected from 225 birds belonging to 20 host species. The following four passerine species that have not yet been subject to detailed reservoir competence analyses were investigated: Nightingale (Luscinia megarhynchos), Dunnock (Prunella modularis), Chiffchaff (Phylloscopus collybita) and Reed warbler (Acrocephalus scirpaceus). Borrelia DNA was analysed in attached ticks and for one species, the Nightingale, blood samples were included. Borrelia DNA was amplified by means of the polymerase chain reaction (PCR) targeting the ospA gene of B. burgdorferi s. l. and 1-2 larvae per bird were analysed. On the basis of one larva per individual bird, Borrelia DNA could be detected in six out of nine larval ticks from the Nightingale, in one out of ten ticks from the Dunnock, in three of nine ticks from the Chiffchaff, and in two out of 21 larval ticks from Reed warblers. Five out of nine ticks removed from Robins Erithacus rubecula in winter were found to be Borrelia positive. Blood samples of Nightingales caught during the breeding period were ospA-gene-positive in 71 of 138 birds (51%).