Daily temperature fluctuations influence West Nile Virus transmission by Culex tarsalis

Temperature drives arbovirus transmission and climate change is expected to affect this process significantly. While previous studies have shown that temperature influences West Nile virus (WNV) infection, dissemination, and transmission, they often rely on constant temperature conditions. This overlooks natural daily fluctuations that shape vector-pathogen interactions. The nonlinear relationship between temperature and transmission traits suggests that fluctuating temperatures produce phenotypes distinct from those at constant temperatures. Here, we hypothesize that field-relevant variations in mean temperature and diurnal temperature range (DTR) influence the vector competence of Culex tarsalis for WNV. To test this hypothesis, we exposed Cx. tarsalis to a WNV-infected blood meal and maintained them under various temperature regimes. A 12°C DTR was simulated using incubators programmed with a temperature model to mimic field-relevant temperature fluctuations. Every three days over 24 days, 24 mosquitoes were sampled. Virus presence in bodies, legs/wings, and saliva were assessed to estimate infection, dissemination, and transmission, respectively. Our findings revealed that constant and fluctuating temperatures influence the likelihood of WNV infection in mosquitoes but in different ways. Constant optimal temperature increased the likelihood of mosquito infection, while fluctuating temperatures around the optimal range reduced the probability of infection. Our analysis also revealed that mosquito infection probability increases with days post-infection, highlighting the importance of time in understanding infection dynamics. Understanding how realistic temperature variations affect Cx. tarsalis vector competence is crucial for predicting climate change impacts on WNV transmission.