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.

We investigated the impact of the kdr genotypes on the survival rate of mosquitoes exposed to insecticides in the main malaria vectors Anopheles coluzzii and An. gambiae s.s.. The genotype-phenotype interaction was investigated following two experimental designs; the first one consisted to determine the survival rate of well-characterized adult mosquito strains sharing different kdr genotypes but same genetic background to various insecticides, whereas the second one consisted to expose wild mosquitoes to the same insecticides. Two to five days old adult females were exposed to DDT (4%), deltamethrin (0.05%), and permethrin (0.75%) following WHO protocols. Alive and dead specimens were kept separately to screen the kdr mutations 1014F. The correlation between the kdr genotype and the survival rate to insecticides was investigated in An. coluzzii and An. gambiae s.s. using a logistic regression model. In the laboratory strains, after exposure to DDT and permethrin, the survival rate was significantly higher in F/F individuals comparing to L/F and L/L individuals (p<0.05). A perfect correlation was observed between the survival rate and the genotype in An. gambiae s.s.. The survival chance in this population was multiplied by 1.9 [1.2; 2.8] for L/F and 3.2 [2.1; 4.7] for F/F individuals after exposure to DDT; and 3.7 [1.8; 7.3] for L/F and 9 [4.8; 17.0] for F/F individuals after exposure to permethrin. In the wild population of An. coluzzii, the survival rate correlated with the genotype after exposure to permethrin and was significantly higher in F/F individuals comparing to L/F and L/L individuals (p<0.05). In L/F and F/F individuals, the survival chance was respectively multiplied by 2.7 [1.4; 5.8] and 3.2 [1.4; 6.9] after exposure to DDT; 2.1 [1.0; 4.1] and 4.1 [2.3; 8.7] after exposure to permethrin; and 2.5 [1.1; 5.3] and 3.9 [1.9; 8.0] after exposure to deltamethrin. Overall, the mosquito survival rates were significantly higher in wild population comparing to laboratory strains after exposure to pyrethroid insecticides. These results suggest that additional mechanisms such as metabolic resistance might contribute to a large extend to phenotypic resistance in malaria vectors.