Culex quinquefasciatus mosquito has developed several resistant mechanisms to the main families of insecticides used in public health. Among these mechanisms, the insensitive acetyl cholinesterase (Ace.1R) confers cross resistance to organophosphorous and carbamates. Fortunately, in an insecticide-free environment, this mutation is associated with a severe genetic cost that affects different biological systems. In insects, the saliva contains bioactive molecules (vasodilatators, anticlotting and anti-hemostatic proteins) which permit a successful blood meal and also facilitate pathogen transmission. In this context, we studied the differential expression of salivary proteins between susceptible and carbamate-resistant (Ace.1R) strains of Cx. quinquefasciatus having a same genetic background. Electrophoresis on acrylamid gel was used to determinate the quantity and quality of salivary proteins expression. The results showed that three majority saliva proteins of the D7 family have lower expression in the resistant strain compared to the susceptible strain. Conversely, ten enzymes involved in metabolic reactions, were up regulated in the resistant strain. This differential expression according to the resistant status of the mosquito may have a repercussion on the biting behaviour and on the transmission of parasites/virus to vertebrate hosts. The next step will consist to study using a video based analysis system the feeding behaviour of susceptible (Ace1SS) and resistant (Ace1RR) mosquitoes in flying chambers. These studies will provide new elements to develop alternative insecticide resistance management strategies in Culex mosquito.

For better management of the use of insecticide in public health against Culex quinquefasciatus, an arboviral and filarial vector, a study was conducted at Natitingou, a town located in northern Benin, from October 2015 to March 2016, to evaluate the susceptible of this mosquito to insecticides and the mechanisms of resistance developed. The protocol was based on mosquito collection during both dry and rainy seasons across the four areas selected in northern Benin. Bioassays were performed on adult mosquitoes collected from the field to assess the susceptibility of filarial vectors to insecticide-impregnated papers (permethrin 0.75%, delthamethrin 0.05%, DDT 4%, and bendiocarb 0.1%) following WHOPES guidelines. Moreover, mosquitoes from the susceptible tests were used to search for the presence of the knock down resistance (Kdr) and the Acethylcholinesterase (Ace-1R) mutations. Finally, F1 generation of the wild population of Cx. quinquefasciatus were used for biochemical analysis to target Mixed Function Oxidase (MFO), non-speci?c esterase (NSE) and glutathione-S-transferases (GST) enzymes. This research showed: 1)-A wide spread of resistance to permethrin, delthamethrin and DDT was found in samples of Cx. quinquefasciatus despite the collection areas with 4%; 7% ; 19% and 60% as average of mortality respectively with DDT, permethrin, deltamethrin and bendiocarb; 2)- The kdr mutation was detected in all areas at various frequencies (0.8 to 0.88) whereas the Ace-1 mutation was found at a very low frequency (? 5%); 3) - Enzymes activities (oxidase, esterase and glutathion-S-transferases) were detected in all mosquito populations despite the areas of collection. This work has highlighted the high resistance of Cx. quinquefascitus to the 3 classes of insecticides used in public health. Moreover, the high frequency of kdr and the presence of enzyme activity in Cx. quinquefasciatus will augment the existing data on the insecticide resistance of filariasis vectors and will be useful for making decision to control this mosquito.