LYME-DISEASE SPIROCHETES IN TICKS COLLECTED FROM BIRDS IN MIDWESTERN UNITED-STATES

In a tick-spirochete survey conducted from fall 1989 through fall 1992 in northwestern Wisconsin, 4,256 birds (composed of 91 species) were examined for ticks. Infestations were recorded for 400 birds (composed of 30 species). Of 1,184 ticks taken from 335 birds (composed of 26 s pecies), GO (5%) Haemaphysalis leporispalustris (Packard) fi om 8 spec ies of birds were infected with the Lyme disease spirochete, Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner. Similar surv eys conducted in 1990 and 1991 ill Minnesota and Michigan yielded 223 H. leporispalustris from 61 birds (composed of 23 species), all free o f spirochetes. However, 1 B. burgdorferi-infected Ixodes scapularis (S ay) was found on 1 bird species in Minnesota. Most ticks were collecte d in fall from ground-foraging birds such as thrushes and sparrows. Th ese results confirm that tick-infested birds are important in dissemin ating Lyme disease spirochetes and may also play a role as soul ces fo r infecting ticks.