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Résistance aux insecticides : importance dans la transmission du virus chikungunya par les moustiques Aedes aegypti

Abstract : The mosquito Aedes aegypti is well known as the main vector of Chikungunya, in absence of effective vaccinations and available treatments, mosquito control strategy remains the principal prevention and defense measures for disease control. Nevertheless, the problem of resistance to insecticides is worsening especially because of more and more frequent chemical fights against intense arbovirus outbreaks in the world. We are interested in understanding the effects of resistance in the context of transmission of the disease, and struggle to establish the reasonable compromise between the effectiveness of the vector control strategy and the increase in resistance.From the mosquito population of Ile Royale which was considered as the least resistant population in French Guiana, 4 mosquito lines IR03, IR05, IR13 and IR36 with different resistance profiles to the deltamethrin insecticide have been isolated successfully, biologic and molecular tests were carried out to characterize the resistance mechanisms between them in regarding with their phenotypes and genotypes. The results indicated that IR03 presented only a metabolic resistance, that IR05 harboured both kdr and metabolic resistance, and that IR13/36 showed a moderate metabolic resistance.More than 600 females were orally infected with Chikungunya virus using an artificial engorged system. For each individual, 3 sets of samples (midgut, head and saliva) are collected independently to quantify the presence of virus, in order to define its vector competence by three parameters: the infection rate, the dissemination rate and the transmission rate. The results show that there were significant differences in vector competence, more specifically between the dissemination rate from the midgut to the head over time, which is lower in the more resistant line.Then, expression level of certain genes (CYP 6BB2, CYP 6N12, GST2, Trypsin) which were associated with deltamethrin resistance were measured on the midgut at 7 days after infectious blood meal. Combined with the information of the kdr genotype, we propose that different mechanisms of resistance can influence not only the barrier of the midgut, but also affect the entire spread pathway of the virus to develop in the mosquito body from the midgut to the saliva.Finally, regarding the cost of resistance, the isofemale lines manifested more clearly in terms of population reproduction than immature development including larval development time, larval and nymphal mortality, and the sex ratio post-emergence.Overall, although this research requires more functional validations or supporting experimentations, the data obtained could provide a better understanding of the interactions between insecticide resistance and vector capacity in mosquitoes Aedes aegypti and supply some useful information to improve the current vector control.
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Lanjiao Wang. Résistance aux insecticides : importance dans la transmission du virus chikungunya par les moustiques Aedes aegypti. Biologie animale. Université de Guyane, 2018. Français. ⟨NNT : 2018YANE0007⟩. ⟨tel-02612568⟩

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