The expanding distribution of Ixodes scapularis and associated pathogens in the Chicago, IL, metropolitan area
The geographic distribution of Lyme disease in the United States has increased considerably since the first description of the illness in the 1970s. The primary vector of Lyme disease, the tick Ixodes scapularis (Acari: Ixodidae), has expanded its range concurrently with the disease including into urban landscapes. To investigate landscape factors that may influence the colonization of I. scapularis and its associated pathogens in an urban ecosystem, 45 sites were sampled along three transects spanning the urban-to-rural human land use gradient in the Chicago, Illinois, metropolitan area. I collected four species of ticks (88% were I. scapularis) which exhibited variable infection rates for six pathogens, including Borrelia burgdorferi, the causative agent of Lyme disease, and B. lonestari and B. miyamotoi, both reported for the first time in Illinois. Logistic regression modeling indicated the presence of I. scapularis was positively correlated with forest land cover and negatively correlated with developed land cover, while the presence of B. burgdorferi was positively correlated with forest land cover. Neither the presence of the tick or the pathogen were correlated with distance to the nearest major river way. This study suggests that the range of I. scapularis and its pathogens have expanded in the Chicago metropolitan area since previous studies were conducted, including into forested urban areas near to the urban core. As tick and pathogen continue to colonize new areas, active monitoring and increased public education will be needed to protect vulnerable human populations.
Ixodes scapularis, Lyme disease, Borrelia burgdorferi, urbanization, habitat fragmentation
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign