Influence of Avian Distributions on West Nile Virus Infection Rates

Abstract

Evidence has shown that human infection rates for West Nile virus are largely dependent on viral amplification that occurs between competent avian host species and mosquito vectors. The threat of West Nile virus to humans is influenced by the diversity and competence of avian host species available to the mosquito vectors. This study used data collected through avian surveys in Montana to analyze the diversity and competence of avian species in those areas. These data were compared to existing GIS model predictions of avian diversity and avian viral competence in Montana to test the accuracy of the model. The GIS model diversity predictions were then compared to the infection rates for avian survey locations, sites that tested positive for West Nile virus, and sites where the primary vector species C. tarsalis was found. It was hypothesized that areas with low avian diversity and high viral competence of avian species would be associated with increased infection rates, whereas high diversity and low competence would be associated with lower infection rates. In this study, the GIS model appeared to be an accurate indicator of avian diversity, and in all cases an amplification effect was observed in which sites containing greater avian diversity appeared to have an increased risk of West Nile virus. However, it is still unclear how significant the role of avian viral competency is in viral amplification and dilution.