West Nile virus (WNV) has become the most epidemiologically important mosquito-borne disease in the United States, causing ~50,000 cases since its introduction in 1999. Transmitted primarily by Culex species, WNV transmission requires the complex interplay between bird reservoirs and mosquito vectors, with human cases the result of epizootic spillover. To better understand the intrinsic factors that drive these interactions, we have compiled infection data from sentinel chickens, mosquito vectors, and human cases in Iowa over a 15 year period (2002–2016) to better understand the spatial and temporal components that drive WNV transmission. Supplementing these findings with mosquito abundance, distribution, and host preferences data, we provide strong support that Culex tarsalis is the most important vector of human WNV infections in the region. Together, our analysis provides new insights into WNV infection patterns in multiple hosts and highlights the importance of long-term surveillance to understand the dynamics of mosquito-borne-disease transmission.

The mosquito fauna of Iowa has been extensively investigated over several decades, providing a wealth of information regarding species distributions, relative abundance, temporal activity patterns, and identifying vectors of medical importance. However, these investigations have had unequal coverage, leaving the mosquito fauna in some parts of the state, including southern Iowa, largely uncharacterized. With the heightened public health threat of Zika virus in the summer of 2016, greater emphasis was placed on surveying for two potential Zika virus vectors: Aedes (Stegomyia) albopictus (Skuse) and Aedes (Stegomyia) aegypti (Linnaeus). Southern Iowa became an area of interest due to the range of Ae. Albopictus, potentially extending into this part of the state. Employing CO2-baited Centers for Disease Control and Prevention light traps and BG-Sentinel traps, our targeted trapping efforts in southern Iowa did not yield either Ae. albopictus or Ae. aegypti. However, the geographical expansion of our trapping efforts did lend valuable insights into the mosquito fauna of southern Iowa. Mosquito species such as Aedes atropalpus (Coquillett), Culex erraticus (Dyar and Knab), and several Psorophora species once presumed rare or uncommon in the state were found to be more prevalent in this ecologically diverse region, augmenting our understanding of mosquito distributions in the state. Moreover, these surveillance efforts established baseline data for continued monitoring of the potential introduction and spread of invasive mosquito species in Iowa as part of an integrated mosquito management program.

West Nile virus (WNV) has become the most epidemiologically important mosquito-borne disease in the United States, causing ∼50,000 cases since its introduction in 1999. Transmitted primarily by Culex species, WNV transmission requires the complex interplay between bird reservoirs and mosquito vectors, with human cases the result of epizootic spillover. To better understand the intrinsic factors that drive these interactions, we have compiled infection data from sentinel chickens, mosquito vectors, and human cases in Iowa over a 15 year period (2002-2016) to better understand the spatial and temporal components that drive WNV transmission. Supplementing these findings with mosquito abundance, distribution, and host preferences data, we provide strong support that Culex tarsalis is the most important vector of human WNV infections in the region. Finally, we identify underlying climatic factors (temperature and drought) that are associated with inter-annual trends in WNV intensity. Together, our analysis provides new insights into WNV infection patterns in multiple hosts and highlights the importance of long-term surveillance to understand the dynamics of mosquito-borne-disease transmission.