Dehydration stress and Mayaro virus vector competence in Aedes aegypti

The mosquito Aedes aegypti is a competent vector of multiple pathogens, including dengue, Zika, yellow fever, chikungunya, and Mayaro viruses. Ae. aegypti is highly invasive and is currently present in the Americas, Oceania, Asia, and Europe, but its distribution and the pathogens it transmits are expected to change due to climate change. Relative humidity (RH) is an environmental variable that affects mosquito biology and distribution and can differ between location, habitat, and season, with mosquitoes facing significant variation in RH during their lifespan. Low relative humidity can induce dehydration in mosquitoes, leading to alterations in physiological and behavioral responses relevant to pathogen transmission, such as blood-feeding and host-seeking behavior. In this study, we evaluated the short- and long-term effects of low RH shock on mortality and Mayaro virus infection and vector competence in Ae. aegypti. Our results show that exposure to dehydration does not impact viral titers, nor infection, dissemination, and transmission rates in mosquitoes infected with Mayaro virus. However, we detected a significant effect of humidity shock on mosquito mortality and blood-feeding frequency, regardless of infection status. The previously observed effects of higher feeding during dehydration and the current observation of altered survival, along with no impact on vector competence, suggest that the impact of dehydration on viral transmission in mosquitoes will likely be complex.