Sublethal insecticide exposure and temperature interact to shape West Nile virus transmission potential of Culex pipiens

Human activities drive climate change and pollution, affecting vector distribution and our understanding of vector-borne diseases. Insecticides are present in surface waters, leading to potential sublethal exposure of vector species during their juvenile aquatic stages. Sublethal exposure can impact the behavior and physiology of vectors, including traits influencing disease transmission. This study aimed to determine how sublethal permethrin exposure and temperature interact to influence parameters that estimate West Nile virus transmission potential for Culex pipiens. Culex pipiens larvae were reared under standard insectary conditions (27.6 ± 0.91⁰C, 70 ± 8% relative humidity, and 16 L:8 D photoperiod) and exposed to a sublethal concentration of permethrin (0.01 mg/L). Upon eclosion, adults were transferred to environmental chambers set at 25 ⁰C and 29 ⁰C to measure life history traits (survival, fecundity) and their vector competence. Permethrin-exposed Culex pipiens larvae took longer to mature, and the resulting adult females survived longer compared to controls. The higher temperature resulted in higher infection and dissemination rates and increased viral detection within mosquito tissues. We found that sublethal insecticide exposure and temperature interact to affect West Nile virus transmission. At 29 °C, control mosquitoes exhibited the lowest transmission potential, whereas mosquitoes exposed to permethrin during the larval stage exhibited higher transmission potential. This experiment shows that larval sublethal effects and adult ambient temperature affect the parameters of vectorial capacity. These findings have implications for environmental and public health, as residual insecticides may unintentionally influence vectors’ ability to transmit diseases, especially in environments exposed to rising temperatures.