Ixodes scapularis (Acari : Ixodidae): Abundance and rate of infection withBorrelia burgdorferi in four state parks in Wisconsin

Four state parks located in Lyme disease endemic regions of Wisconsin were surveyed for the presence of Ixodes scapularis Say during May and June of 1 998 by drag sampling along hiking trails. Nymphal abundance varied between parks, with the average number of nymphs encountered in 1 h ranging from 6. 2 +/- 3.8-47.1 +/- 36.3 (mean +/- SD). Questing nymphs were tested for the presence of Borrelia burgdorferi by culture in BSK medium and 7-12% was fou nd to be infected. The average risk of encountering an infected nymph (ento mologic risk index) ranged from 0.5 to 5.2 infected nymphs per hour. The hi ghest entomological risk index was recorded from a small island park in nor thwestern Wisconsin during the last week in May (8.0 infected nymphs per ho ur). These results indicate a lower risk for human Lyme disease exposure in Wisconsin state parks in comparison with highly endemic areas of the north eastern United States.