Borrelia burgdorferi infection of ticks in some regions of Poland

: Ixodes ricinus and Dermacentor reticulatus ticks were collected by flagging from the vegetation at five different locations in Poland in May 1994. I. ricinus (n191) and D. reticulatus (n48), as well as 24 Argas reflexus collected from Katowice, Kornie, Szcyglice, Urwitalt and Zwierzyniec, were examined for the presence of Borrelia spirochetes by the indirect immunofluorescent antibody test (IFA). Borrelia were found in adult I. ricinus ticks at all 5 collection sites. Nine out of 39 I. ricinus males (23%) and 16 out of 72 I. ricinus females (22.2%) were infected. In addition, 2 out of 72 I. ricinus larvae (2.7%) were heavily infected, whereas none of the D. reticulatus and A. reflexus contained Borrelia. These results show that I. ricinus is also in Poland the main vector of Lyme disease-causing spirochetes. The finding that some larvae are also infected merits further investigations into the relative role of transovarial transmission of Borrelia in field populations of I. ricinus ticks.