Relative Influence of Land Use, Mosquito Abundance, and Bird Communities in Defining West Nile Virus Infection Rates in Culex Mosquito Populations

Simple Summary West Nile virus (WNV) is transmitted by mosquitoes and maintained in bird populations. However, it is less clear why some geographic locations consistently serve as "hotspots" for increased WNV transmission. To address this question, we examined land use as well as mosquito and bird community metrics at sites across central Iowa. Our data suggest that WNV activity in mosquitoes is most heavily influenced by the abundance of Culex pipiens group mosquitoes during late summer, with landscape ecology having less defined impacts. Our data also suggest that bird community metrics have little influence on WNV infections in mosquitoes. Together, these results provide new information on the ecological and host factors that most heavily influence WNV transmission. Since its introduction to North America in 1999, the West Nile virus (WNV) has resulted in over 50,000 human cases and 2400 deaths. WNV transmission is maintained via mosquito vectors and avian reservoir hosts, yet mosquito and avian infections are not uniform across ecological landscapes. As a result, it remains unclear whether the ecological communities of the vectors or reservoir hosts are more predictive of zoonotic risk at the microhabitat level. We examined this question in central Iowa, representative of the midwestern United States, across a land use gradient consisting of suburban interfaces with natural and agricultural habitats. At eight sites, we captured mosquito abundance data using New Jersey light traps and monitored bird communities using visual and auditory point count surveys. We found that the mosquito minimum infection rate (MIR) was better predicted by metrics of the mosquito community than metrics of the bird community, where sites with higher proportions of Culex pipiens group mosquitoes during late summer (after late July) showed higher MIRs. Bird community metrics did not significantly influence mosquito MIRs across sites. Together, these data suggest that the microhabitat suitability of Culex vector species is of greater importance than avian community composition in driving WNV infection dynamics at the urban and agricultural interface.