.|  Baltimore Ecosystem Study
Understanding spatio-temporal heterogeneities in mosquito communities and vector-borne disease risk
  • Shannon LaDeau, Cary Institute of Ecosystem Studies;
  • John Wallace, Millersville University

Figure 1. Mosquito Sampling At Carroll Park
Photograph: Dan Dillon  
The emergence of West Nile virus (WNV) in New York City in 1999 reawakened many Americans to the threats of vector-borne infectious disease. The broad goal of this study is to investigate how human land use patterns influence the persistence and amplification (increase) of WNV in the environment. The persistence of the WNV pathogen relies on complex ecological interactions among at least three populations (pathogen, avian hosts, and mosquito vectors). 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 on pathogen dynamics are complex, and likely to alter the ecological processes that define spatio-temporal patterns in composition and abundance of mosquito species and human disease risk.
There are over sixty species of mosquitoes in the Mid-Atlantic region but only a few are important disease vectors. In the first year of this work (2009), we began a pilot study to test the hypothesis that urban breeding habitats support fewer mosquito species but greater abundances of vector species (Figure 1). All mosquitoes require water to breed. Temporary pools of standing water near stream banks were sampled monthly from sites surrounded by urban (paved) and rural (forested) landscapes. Early results are shown below. We identified ten mosquito species. Four occurred in both urban and rural samples, including Culex pipiens. Three potentially important bridge vectors (mosquitoes that feed on both birds and humans) were found only in urban sites (Aedes vexans, Aedes albopictus, Ochlerotatus japonicas). A higher relative abundance of macro-invertebrates known to feed on mosquito larvae (i.e., dragonfly larvae) were also found in the rural site.

Figure 2. Mean mosquito abundance (left axis) and predator: mosquito ratio (right axis) from urban and rural water sources, early summer 2009. Enzootic (bird-feeding) and bridge (bird and human feeders) vectors are separated from other mosquito species.
Figure: Shannon LaDeau