PRELIMINARY EVALUATION OF THE INSECTICIDE SUSCEPTIBILITY IN THE CULICID FAUNA, PARTICULARLY MALARIA PLASMODIUM AND ARBOVIRUS VECTORS IN THE REGION OF MOUILA, SOUTH-WEST GABON

Objective: To assess the susceptibility status of the culicid fauna in Mouila and its environs (southwest Gabon). Methods: This study was carried out in august 2017 and focused on insecticides recommended for public health that contain DDT (4%), deltamethrin (0.05%), permethrin (0.75%) and bendiocarb (0.1%). The Anopheles and Culex larvae were collected from different breeding sites of the oil palm plantations and neighboring villages, in the Mouila area. All larvae were transported to the laboratory and reared to the adult stage. The susceptibility tests were performed on the emerging adult mosquitoes using unfed adult females aged 2 to 4 days old. These mosquitoes were exposed to insecticides according to WHO standard protocol. Results: Mosquitoes showed a susceptibility to carbamates (bendiocarb; mortality=100%) and a resistance to organochlorines (DDT; mortality=89%) and pyrethroids (deltamethrin and permethrin; mortalities=71% and 79%). Moreover, the susceptibility tests carried out on Anopheles mosquitoes revealed a resistance to pyrethroids (deltamethrin and permethrin) and organochlorines (DDT), with the respective mortality rates of 76%, 9 % and 7%. Populations of both Culex and Anopheles adult mosquitoes were resistant to the tested insecticides that contain DDT and pyrethroids. The resistance level of Anopheles mosquitoes to permethrin and DDT were very high compared with those of Culex mosquitoes. Conclusion: The results of these analyses will allow a better understanding of the resistance mechanisms developed by these insect vectors in the Mouila region.Molecular analyses of the resistant specimens are in process to determine the genes involved in the resistance to these insecticides