West Nile Virus Infection Rates and Avian Serology in East-Central Illinois

Illinois Natural History Survey, University of Illinois, Champaign, IL 61820, USA.
Journal of the American Mosquito Control Association (Impact Factor: 0.95). 06/2013; 29(2):108-22. DOI: 10.2987/12-6318R.1
Source: PubMed


Understanding the geographic role of different species of mosquito vectors and vertebrate hosts in West Nile virus (WNV) transmission cycles can facilitate the development and implementation of targeted surveillance and control measures. This study examined the relationship between WNV-antibody rates in birds and mosquito infection rates and bloodfeeding patterns in east-central Illinois. The earliest detection of WNV-RNA by reverse transcription-polymerase chain reaction TaqMan was from Culex restuans; however, amplification typically coincided with an increase in abundance of Cx. pipiens. Trap type influenced annual estimates of infection rates in Culex species, as well as estimation of blood meal source. Bird species with the highest WNV-antibody rates (i.e., Mourning Doves [Zenaida macroura], Northern Cardinals [Cardinalis cardinalis], American Robins [Turdus migratorius], and House Sparrows [Passer domesticus]) were also the common species found in Culex blood meals. Although antibody rates were not directly proportional to estimated avian abundance, the apparent availability of mammal species did influence proportion of mammal to bird blood meals. Antibody prevalence in the American Robin was lower than expected based on the strong attraction of Culex to American Robins for blood meals. Age-related differences in serology were evident, antibody rates increased in older groups of robins and sparrows, whereas 1st-year hatch and older adults of Mourning Doves and Northern Cardinals had equally high rates of antibody-positive serum samples. The vector and host interactions observed in east-central Illinois (Champaign County), an urban area surrounded by agriculture, are compared to studies in the densely population areas of southern Cook County.

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    • "Many studies have reported differences in antibody prevalence between juveniles and adult birds. In many cases, adult bird antibody prevalence is higher than in juveniles (Gibbs et al. 2006; Hamer et al. 2008; Lampman et al. 2013), which is explained by the additive effect of adult birds being exposed in prior years. However, few studies consider that antibody-negative adult birds could represent false negatives, due to waning antibodies, which could confound analyses that rely on antibody status to infer population metrics, such as mortality (Ward et al. 2010; Kilpatrick et al. 2013). "
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    ABSTRACT: Antibody duration, following a humoral immune response to West Nile virus (WNV) infection, is poorly understood in free-ranging avian hosts. Quantifying antibody decay rate is important for interpreting serologic results and for understanding the potential for birds to serorevert and become susceptible again. We sampled free-ranging birds in Chicago, Illinois, USA, from 2005 to 2011 and Atlanta, Georgia, USA, from 2010 to 2012 to examine the dynamics of antibody decay following natural WNV infection. Using serial dilutions in a blocking enzyme-linked immunosorbent assay, we quantified WNV antibody titer in repeated blood samples from individual birds over time. We quantified a rate of antibody decay for 23 Northern Cardinals (Cardinalis cardinalis) of 0.198 natural log units per month and 24 individuals of other bird species of 0.178 natural log units per month. Our results suggest that juveniles had a higher rate of antibody decay than adults, which is consistent with nonlinear antibody decay at different times postexposure. Overall, most birds had undetectable titers 2 yr postexposure. Nonuniform WNV antibody decay rates in free-ranging birds underscore the need for cautious interpretation of avian serology results in the context of arbovirus surveillance and epidemiology.
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    The American journal of tropical medicine and hygiene 12/2014; 92(2). DOI:10.4269/ajtmh.14-0291 · 2.70 Impact Factor