Ixodes scapularis (Acari: Ixodidae) Distribution Surveys in the Chicago Metropolitan Region

Considering recent studies confirming an increased risk of contracting Lyme disease near metropolitan Chicago, we surveyed a more comprehensive area to assess whether the geographical distribution and establishment of Ixodes scapularis (Say) populations across northeast Illinois are widespread or limited in occurrence. From May through October 2008 and from April through October 2009, 602 I. scapularis ticks of all three life stages (larva, nymph, adult) were collected from sites in Cook, DuPage, Lake, and McHenry counties in northeast Illinois. The surveys were conducted by drag sampling vegetation in public-access forested areas. I. scapularis comprised 56.4% of ticks collected (n = 1,067) at 17 of 32 survey sites. In addition, four other tick species were incidentally collected: Dermacentor variabilis (Say), Haemaphysalis leporispalustris (Packard), Ixodes dentatus (Marx), and Amblyomma americanum (L.). This study updates the I. scapularis distribution in northeast Illinois. Our random sampling of suitable tick habitats across a large geographic area of the Chicago metropolitan area suggests a widespread human exposure to I. scapularis, and, potentially, to their associated pathogens throughout the region. These results prompt continued monitoring and investigation of the distribution, emergence, and expansion of I. scapularis populations and Borrelia burgdorferi transmission within this heavily populated region of Illinois.