PCR detection of granulocytic Ehrlichiae in Ixodes ricinus ticks and wild small mammals in western Switzerland

The presence of granulocytic ehrlichiae was demonstrated by PCR in Ixodes r icinus ticks and wild small mammals in Switzerland in two areas of endemici ty for bovine ehrlichiosis. Six ticks (three females and three nymphs) (1.4 %) of 417 I. ricinus ticks collected by flagging vegetation contained ehrli chial DNA. A total of 201 small mammals from five species, wood mouse (Apod emus sylvaticus), yellow-necked mouse (Apodemus flavicollis), earth vole (P itymys subterraneus), bank vole (Clethrionomys glareolus), and common shrew (Sorex araneus), were trapped. The analysis of I. ricinus mammals collecte d on 116 small mammals showed that nine C. glareolus voles and two A. sylva ticus mice hosted infected tick larvae. In these rodents, granulocytic ehrl ichia infection was also detected in blood, spleen, liver, and ear samples. Further examinations of 190 small mammals without ticks or with noninfecte d ticks showed the presence of ehrlichial DNA in spleen and other tissues f rom six additional C. glareolus, three A. flavicollis, and one S. araneus m ammals. This study suggests that A. sylvaticus, A. flavicollis, S. araneus, and particularly C. glareolus are likely to be natural reservoirs for gran ulocytic ehrlichiae. Partial 16S rRNA gene sequences of granulocytic ehrlic hiae from ticks and rodents showed a high degree of homology (99 to 100%) w ith granulocytic ehrlichiae isolated from humans. In contrast, groESL heat shock operon sequence analysis showed a strong divergence (approximately 5% ) between the sequences in samples derived from rodents and those derived f rom samples from questing ticks or from other published ehrlichia sequences . Dual infections with granulocytic ehrlichia and Borrelia burgdorferi were found in ticks and small mammals.