Effects of Interactions Between Insecticide Resistance Genes and the Bacteria Wolbachia in the Transmission of Pathogens By Mosquito Vectors

These last few years have witnessed an increasing interest in Arthropod-borne viruses (arboviruses) transmitted by mosquitoes due to occurrence of epidemic outbreaks outside their natural range of distribution. To date, the control of mosquito natural populations is one of the few available strategies limiting arboviruses transmission and the use of insecticides plays a key role in this purpose. However, the widespread development of different mechanisms of insecticide resistance in response to frequent implementation of insecticides is considered as a serious public health challenge. Mutations that confer insecticide resistance are often associated to fitness cost and changes in mosquito microbiota. It has been demonstrated that insecticide-resistant mosquitoes present a higher load of the bacteria Wolbachia compared to insecticide-susceptible individuals. As Wolbachia have been found to interfere with the replication of arboviruses such as dengue, chinkungunya and West-Nile viruses, a comprehensive understanding of the transmission of these pathogens requires deciphering the tripartite association between insecticide resistance genes, Wolbachia and viruses in mosquitoes. The overall goal of this proposal is to elucidate the effects of the interactions between insecticide resistance genes and Wolbachia in the transmission of Rift Valley Fever virus (RVFV) and West-Nile virus (WNV) by the Culex pipiens mosquito. In this objective, four specific aims will be achieved: (i) to identify the insecticide-resistant genes associated with increased Wolbachia densities and to examine consequences on some life-history traits such as larval mortality and adult longevity, (ii) to explore underlying genetic molecular mechanisms involved in the observed phenotypes, (iii) to estimate whether the presence of resistance genes can modify the vector competence to RVFV and WNV, and (iv) to evaluate the relationship between vector competence, insecticide resistance genes and Wolbachia diversity in natural populations of Cx. pipiens. Overall, this project will provide important insights for the monitoring and the evaluation of the risk of emergence and spread of arboviruses.

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