Susceptibility status of Anopheles gambiae complex in NNEWI community, Anambra state

Abstract

Insecticide resistance in Anopheles mosquito is a major concern for vector control interventions in Nigeria. The present base-line study was carried out in Nnewi community, Nnewi North L.G.A., Anambra State, South-east Nigeria to investigate the insecticide susceptibility status of wild Anopheles gambiae s.l. to the four classes of insecticide used in vector control interventions. Anopheles larvae collected from different breeding sites in the community were reared to adults in the insectary and were morphologically identified following standard protocols. Two to five-day old adult female mosquitoes were exposed to different doses of organochlorine (4% DDT), organophosphate (0.25% pirimiphos-methyl and 5.0% malathaion), carbamate (0.1% propoxur and 0.1% bendiocarb) and pyrethroid (0.05% deltamethrin, 0.75% permethrin) insecticides using WHO susceptibility assay protocol. Data generated were subjected to probit analysis and analysis of variance. The organochlorine insecticide (DDT) had the highest knockdown time KDT50 (113.8 minutes) and KDT95 (182.1 minutes) while the carbamate insecticide, bendiocarb had the least KDT50 (8.97 minutes) and KDT95 (28.78 minutes). The mosquitoes were totally susceptible to propoxur and bendiocarb. The two pyrethroid used (deltamethrin and permethrin) and organochlorine (DDT) recorded percentage mortalities of 17.5%, 43.75% and 11.25% respectively. The report of organochlorine and pyrethroid resistance in the study area calls for immediate implementation of management action in the study area. The study has also shown that carbamate insecticides may be a suitable alternative to mitigate pyrethroid resistance in mosquito population in the study area.