Status of organophosphate and carbamate resistance in Anopheles gambiae sensu lato from the Sudano Guinean area in the central part of Benin, West Africa

Abstract

Anopheles gambiae, which is the main malaria vector in Benin has developed high level of resistance to pyrethroid insecticides. This raises serious concerns to the future use of long- lasting insecticidal nets (LLIN) and indoor residual spraying (IRS). It is therefore important to seek better and effective resistance management strategies which will use organophosphates or carbamates as alternatives against pyrethroid resistant malaria vectors in the field. Larvae and pupae of A. gambiae s.l. mosquitoes were collected from the breeding sites in Dassa-Zoume and Zogbodomey districts. WHO susceptibility tests were conducted on unfed female mosquitoes aged 2-5 days old. WHO bioassays were performed with impregnated papers with fenitrothion 1%, pirimiphos-methyl 0.25%, and bendiocarb 0.1%. Polymerase chain reaction (PCR) techniques were used to detect species and Ace-1 mutations. A. gambiae Dassa-Zoume populations were susceptible to bendiocarb 0.1% with mortality rate of 99%. A. gambiae Zogbodomey populations were susceptible to pirimiphos-methyl 0.25% and fenitrothion 1% with mortality rates of 98.96 and 99%, respectively. PCR assay revealed that 100% of mosquitoes tested were A. gambiae s.s. The frequencies of Ace-1R mutation in A. gambiae Dassa-Zoume and Zogbodomey were 0%. Carbamates (bendiocarb) and organophosphates (fenitrothion and pirimiphos-methyl) have maintained their efficiency against A. gambiae Dassa-Zoume and Zogbodomey populations. Carbamates (bendiocarb) and organophosphates (fenitrothion and pirimiphos-methyl) have proven to be powerful alternatives against pyrethroid resistant malaria vectors such as A. gambiae Dassa-Zoume and Zogbodomey populations. The use of any of these three compounds in the centre Benin would be successful in malaria vector control.   Key   words:   Anopheles gambiae,   Ace-1,   resistance,   fenitrothion,   pirimiphos-methyl, bendiocarb, Benin.