Evidence of multiple pyrethroid resistance mechanisms in the malaria vector Anopheles gambiae sensu stricto from Nigeria

T.S. Awolola, O.A. Oduola, C. Strode, L.L. Koekemoer, B. Brooke, H. Ranson

Research output: Contribution to journalArticle

89 Citations (Scopus)

Abstract

Pyrethroid insecticide resistance in Anopheles gambiae sensu stricto is a major concern to malaria vector control programmes. Resistance is mainly due to target-site insensitivity arising from a single point mutation, often referred to as knockdown resistance (kdr). Metabolic-based resistance mechanisms have also been implicated in pyrethroid resistance in East Africa and are currently being investigated in West Africa. Here we report the co-occurrence of both resistance mechanisms in a population of An. gambiae s.s. from Nigeria. Bioassay, synergist and biochemical analysis carried out on resistant and susceptible strains of An. gambiae s.s. from the same geographical area revealed >50% of the West African kdr mutation in the resistant mosquitoes but <3% in the susceptible mosquitoes. Resistant mosquitoes synergized using pyperonyl butoxide before permethrin exposure showed a significant increase in mortality compared with the non-synergized. Biochemical assays showed an increased level of monooxygenase but not glutathione-S-transferase or esterase activities in the resistant mosquitoes. Microarray analysis using the An. gambiae detox-chip for expression of detoxifying genes showed five over-expressed genes in the resistant strain when compared with the susceptible one. Two of these, CPLC8 and CPLC#, are cuticular genes not implicated in pyrethroid metabolism in An. gambiae s.s, and could constitute a novel set of candidate genes that warrant further investigation.
Original languageEnglish
Pages (from-to)1139-1145
JournalTransactions of the Royal Society of Tropical Medicine and Hygiene
Volume103
Issue number11
DOIs
Publication statusPublished - 2009

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