High Level of Pyrethroid Resistance in an Anopheles funestus Population of the Chokwe District in Mozambique

Abstract

BackgroundAlthough Anopheles funestus is difficult to rear, it is crucial to analyse field populations of this malaria vector in order to successfully characterise mechanisms of insecticide resistance observed in this species in Africa. In this study we carried out a large-scale field collection and rearing of An. funestus from Mozambique in order to analyse its susceptibility status to insecticides and to broadly characterise the main resistance mechanisms involved in natural populations.Methodology/Principal Findings3,000 F1 adults were obtained through larval rearing. WHO susceptibility assays indicated a very high resistance to pyrethroids with no mortality recorded after 1h30min exposure and less than 50% mortality at 3h30min. Resistance to the carbamate, bendiocarb was also noted, with 70% mortality after 1h exposure. In contrast, no DDT resistance was observed, indicating that no kdr-type resistance was involved. The sequencing of the acetylcholinesterase gene indicated the absence of the G119S and F455W mutations associated with carbamate and organophosphate resistance. This could explain the absence of malathion resistance in this population. Both biochemical assays and quantitative PCR implicated up-regulated P450 genes in pyrethroid resistance, with GSTs playing a secondary role. The carbamate resistance observed in this population is probably conferred by the observed altered AChE with esterases also involved.Conclusion/SignificanceThe high level of pyrethroid resistance in this population despite the cessation of pyrethroid use for IRS in 1999 is a serious concern for resistance management strategies such as rotational use of insecticides. As DDT has now been re-introduced for IRS, susceptibility to DDT needs to be closely monitored to prevent the appearance and spread of resistance to this insecticide.

Restriction to gene flow is associated with changes in the molecular basis of pyrethroid resistance in the malaria vector Anopheles funestus

“…This concern is increased by the presence of resistance to the carbamate bendiocarb, the main alternative to pyrethroids for IRS. The resistance profile described in this study confirms resistance in isolated districts in Malawi (3,12) and is similar to that in neighboring countries, including Mozambique (13,14) and Zambia (4,8), suggesting that pyrethroid and carbamate resistance is widespread in southern Africa, but the genetic mechanisms responsible for this resistance are not uniform. The apparent shift in gene expression in An.…”

Impact of pyrethroid resistance on operational malaria control in Malawi

“…Similar patterns of pyrethroid resistance occur in An. funestus from Mozambique and South Africa (9,21). It is possible that this resistance front has now extended north from Mozambique, or it may have been selected de novo in Malawi.…”

“…funestus (17) and in field samples of An. funestus from Mozambique (21) were carried out to assess whether they were also over expressed in the Malawian An. funestus field samples.…”

Advances and Perspectives in the Study of the Malaria Mosquito Anopheles funestus

“…insecticide treated materials or indoor residual spraying). Anopheles funestus has developed insecticide resistance in many parts of the African continent [61][62][63][64]. To date, An.…”

“…No evidence for the presence of L1014F kdr mutation or G119S Ace-1 mutation has been detected in An. funestus [63,64,71,72]. However, a multiple insecticide resistance profile has been recently observed in Benin [74].…”