| ixodes ricinus density and infection prevalence of borrelia burgdorferi sensu lato along a north-facing altitudinal gradient in the rhône valley (switzerland). | questing ixodes ricinus ticks were sampled monthly along a north-facing altitudinal gradient in the canton of valais, switzerland, from march 2004 to february 2005. tick density and infection with borrelia burgdorferi sensu lato were monitored. ticks were collected by flagging vegetation at three different altitudes (750 m, 880 m, and 1020 m above sea level). ticks were examined for borrelia by polymerase chain reaction (pcr) followed by reverse line blot. at the three altitudes, questing tick a ... | 2007 | 17417957 |