Résumé
Mosquitoes of the Culex pipiens complex are known for their role as vectors for many arboviruses. Among these, Usutu virus (USUV) is an emerging pathogen in Europe that impacts bird species as well as other animal such as humans. To control the spread of arboviruses, vector control is the only affordable way in absence of treatments. But the extensive use of insecticides led to select several resistant alleles that have invaded natural populations. The objective of our study is to determine the potential impact of insecticide resistance on arbovirus transmission and on vector-arbovirus interaction. We investigated the influence of several insecticide resistance alleles on vector competence for USUV and the impact of both resistance and infection on survival and fecundity of Cx. quinquefasciatus. We performed experimental infections of four Cx. quinquefasciatus colonies (one susceptible and three resistants) with USUV EU3 lineage. These colonies differ by the genomic architecture around ace-1 locus conferring resistance to organophosphate but share a common genetic background after introgression with the genome of the susceptible colony. We then used and RNAseq approach to analyze the key genomic components involved in vector competence.The results showed specific effects of genotype on vector competence and life history traits of infected mosquitoes. The susceptible colony was significantly more competent than the three resistant colonies. Survival and oviposition of females varied between the 4 strains. Interaction was found between resistant alleles and USUV infection in these parameters for some of our colonies.Based on these phenotypic results, our experimental design allowed us to conduct a transcriptomic analysis to explore the differential gene expression between mosquitoes colonies and competence status, i.e. competent individuals, non competent and controls groups. This study helped characterizing the genetic factors involved in transmission and virulence and improves our understanding of vector- pathogens interactions.