Volume 80, Issue 2
  • ISSN: 0002-9637
  • E-ISSN: 1476-1645


Recent field studies have suggested that the dynamics of West Nile virus (WNV) transmission are influenced strongly by a few key super spreader bird species that function both as primary blood hosts of the vector mosquitoes (in particular ) and as reservoir-competent virus hosts. It has been hypothesized that human cases result from a shift in mosquito feeding from these key bird species to humans after abundance of the key birds species decreases. To test this paradigm, we performed a mosquito blood meal analysis integrating host-feeding patterns of , the principal vector of WNV in the eastern United States north of the latitude 36°N and other mosquito species with robust measures of host availability, to determine host selection in a WNV-endemic area of suburban Chicago, Illinois, during 2005–2007. Results showed that fed predominantly (83%) on birds with a high diversity of species used as hosts (25 species). American robins () were marginally overused and several species were underused on the basis of relative abundance measures, including the common grackle (), house sparrow (), and European starling (). also fed substantially on mammals (19%; 7 species with humans representing 16%). West Nile virus transmission intensified in July of both years at times when American robins were heavily fed upon, and then decreased when robin abundance decreased, after which other birds species were selected as hosts. There was no shift in feeding from birds to mammals coincident with emergence of human cases. Rather, bird feeding predominated when the onset of the human cases occurred. Measures of host abundance and competence and feeding preference were combined to estimate the amplification fractions of the different bird species. Predictions were that approximately 66% of WNV-infectious became infected from feeding on just a few species of birds, including American robins (35%), blue jays (17%, ), and house finches (15%, ).


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  • Received : 10 Jun 2008
  • Accepted : 06 Oct 2008

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