The emergence of West Nile virus (WNV) in New York City in 1999 reawakened many Americans to the threats of vector-borne infectious disease. In the past decade, WNV has had a persistent and dramatic impact on many North American bird species and has resulted in over 1000 human fatalities. However, the magnitude of avian mortality and human incidence has been positively associated with human-dominated landscapes. The potential effects of landscape modification and interactions with changing climate are complex and likely to alter the ecological processes that define spatio-temporal patterns in composition and abundance of mosquito (vector) species and disease risk. In summer 2009, we collected data in Baltimore, MD to test the hypothesis that urban breeding habitats support fewer mosquito species but greater abundances of WNV vector species. Temporary pools of standing water near stream banks were sampled monthly from sites surrounded by urban (paved) and rural (forested) landscapes.
Results/Conclusions We identified ten mosquito species, four of which occurred in both urban and rural samples, including Culex pipiens. Three potentially important WNV bridge vectors (mosquitoes that feed on both birds and humans) were found only in urban sites (Aedes vexans, Aedes albopictus, Ochlerotatus japonicas). We also sampled macro-invertebrates at these sites to assess the relative predation pressure on mosquito abundance. By mid-summer the predator (i.e., dragonfly larvae) to mosquito ratio was over three-times greater in rural versus urban samples. The overall abundance of mosquito larvae from rural samples was roughly one-third urban abundances, even though the urban sites were dry by August. The majority of increase in urban abundances was due to increased numbers of bridge vectors. Our work thus far indicates that, at least in the Mid-Atlantic region, much of the increase in human (and bird) WNV risk associated with urban landscapes may be attributed to changes in mosquito communities.
