Abstract
The mosquito Aedes aegypti is the primary vector of many disease-causing viruses, including dengue (DENV), Zika, chikungunya, and yellow fever. As consequences of climate change, we expect an increase in both global mean temperatures and extreme climatic events. When temperatures fluctuate, mosquito vectors will be increasingly exposed to temperatures beyond their upper thermal limits. Here, we examine how DENV infection alters Ae. aegypti thermotolerance by using a high-throughput physiological ‘knockdown’ assay modeled on studies in Drosophila. Such laboratory measures of thermal tolerance have previously been shown to accurately predict an insect’s distribution in the field. We show that DENV infection increases thermal sensitivity, an effect that may ultimately limit the geographic range of the virus. We also show that the endosymbiotic bacterium Wolbachia pipientis, which is currently being released globally as a biological control agent, has a similar impact on thermal sensitivity in Ae. aegypti. Surprisingly, in the coinfected state, Wolbachia did not provide protection against DENV-associated effects on thermal tolerance, nor were the effects of the two infections additive. The latter suggests that the microbes may act by similar means, potentially through activation of shared immune pathways or energetic tradeoffs. Models predicting future ranges of both virus transmission and Wolbachia’s efficacy following field release may wish to consider the effects these microbes have on host survival.
Highlights
Mosquitoes are responsible for transmitting a diverse array of human disease-causing viruses such as Zika (ZIKV), chikungunya (CHIKV), West Nile, yellow fever, and dengue (DENV) [1, 2]
DENV and Wolbachia infections increase mosquito thermal sensitivity, causing more rapid death when mosquitoes are exposed to extreme heat
To test whether DENV and or Wolbachia infection alter mosquito thermal sensitivity, we submerged mosquitoes (+/-Wolbachia, +/-DENV) in glass vials in a water bath heated to 42 ̊C, representing the upper critical thermal limit (CTmax) for the mosquitoes, as determined by pilot assays
Summary
Mosquitoes are responsible for transmitting a diverse array of human disease-causing viruses such as Zika (ZIKV), chikungunya (CHIKV), West Nile, yellow fever, and dengue (DENV) [1, 2]. Without effective antiviral drugs or a vaccine for DENV, ZIKV, or CHIKV, vector control has remained the primary strategy for reducing the incidence of these human diseases [7, 8]. Such strategies have relied on insecticide use and larval habitat reduction. A more recent and promising approach involves the use of the insect endosymbiotic bacterium Wolbachia pipientis [9] This self-spreading, vertically inherited bacterium has been transinfected into Ae. aegypti, where it is being released globally into wild populations for biological control (biocontrol) because Wolbachia limits the replication of viruses inside the mosquito, including DENV [10, 11]
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