Abstract: West Nile virus (WNV; Flavivirus, Flaviviridae) is a single-stranded positive-sense RNA virus and is the most common mosquito-borne disease in the contiguous U.S. It is commonly vectored by Culex mosquitoes and is found in a transmission cycle between its amplifying hosts of birds. Incidental hosts of WNV include people and animals. Since the beginning of the 20th century, the earth’s average temperature has increased by 1°C. Ectothermic organisms, such as mosquitoes and the pathogens they transmit, are uniquely susceptible to such increases. Temperature increases are known to alter mosquito life history traits, viral replication, and vector competence, all of which play a role in WNV transmission. The influence of temperature on WNV transmission is multifaceted. Unique interactions among mosquito population, mosquito life history traits, and virus strain are key in determining temperature-dependent WNV transmission. To gain a better understanding of the population-specific effects of temperature and WNV transmission, life history traits were recorded at geographically relevant and future predicted temperatures of field-acquired Culex pipiens from New York State. Data-informed mathematical models indicated differences in peak transmission temperature between upstate and downstate Cx. pipiens, demonstrating the importance of thermal sensitivity on a population level when predicting temperature-dependent WNV transmission. Additionally, it was hypothesized that contemporary WNV, which evolved under increased temperature, may have increased fitness at higher temperatures compared to historic WNV strains. Here, Cx. pipiens vector competence of eight WNV strains was measured at 20°, 24°C, and 28°C. Cx. pipiens were found to have increased vectorial capacity for contemporary strains across temperatures. These results are consistent with temperature-facilitating adaptation in nature and highlight the importance of strain-specific differences in WNV risk under climate change. These studies outline the complex influence of temperature on WNV transmission, demonstrating the importance of unique vector-virus interactions in temperature-dependent vector-borne disease risk.
