Anophelesfunestus is one of the major malaria vectors in Africa. This species has recently re-colonized the Senegal River basin after 30 years of absence with its infection rate increasing from 0.04% in 2004 to 5.07 % in 2006. Therefore we undertook to characterize the new An. funestus populationand evaluate its role in malaria transmission in the Senegal River basin.
Mosquitoes were collected by Human Landing Catches and indoor Insecticide Spray-sheet. The Infection rate and feeding pattern were determined by ELISA and microsatellites were used to determine the genetic structure of An. funestus populations. Microarray, qRT-PCR and pyrosequencing method were used to investigate the resistance mechanism.
Entomological surveys revealed a low infection rate (1/1850) and the entomological inoculation rate was estimated to 2.55 infected bites. The population genetic structure showed low but significant genetic differentiation (Fst estimated from 0.0439 to 0.0682) between the new populations of the Senegal River basin and other populations from Senegal. WHO susceptibility tests revealed this Anopheles funestus population is resistant to lambda-cyhalothrin (72% mortality) and DDT (82% mortality) while a suspected resistance was found against deltamethrin, permethrin, bendiocarb and Dieldrin. A full susceptibility was observed to Malathion and Fenitrothion. We identified that the P450 CYP6M7 is the most up-regulated gene in Lamdda (FC 101.6) and DDT (FC 71.33) resistant samples compared to a laboratory susceptible strain. The A296S RdlR target site mutation was detected in all dieldrin resistant mosquitoes.
This study provides the first report of pyrethroid/DDT resistance in An. funestus from Senegal. Cytochrome P450 are implicated in the metabolic resistance observed. The study findings will allow implementation of a suitable control intervention against this vector in this region.