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Randomized Controlled Trial
. 2015 Mar;29(1):51-9.
doi: 10.1111/mve.12090. Epub 2014 Dec 24.

Trends in the selection of insecticide resistance in Anopheles gambiae s.l. mosquitoes in northwest Tanzania during a community randomized trial of longlasting insecticidal nets and indoor residual spraying

J Matowo  1 , J Kitau, R Kaaya, R Kavishe, A Wright, W Kisinza, I Kleinschmidt, F Mosha, M Rowland, N Protopopoff
Affiliations
Randomized Controlled Trial

Trends in the selection of insecticide resistance in Anopheles gambiae s.l. mosquitoes in northwest Tanzania during a community randomized trial of longlasting insecticidal nets and indoor residual spraying

J Matowo et al. Med Vet Entomol. 2015 Mar.

Abstract

Anopheles gambiae s.l. (Diptera: Culicidae) in Muleba, Tanzania has developed high levels of resistance to most insecticides currently advocated for malaria control. The kdr mutation has almost reached fixation in An. gambiae s.s. in Muleba. This change has the potential to jeopardize malaria control interventions carried out in the region. Trends in insecticide resistance were monitored in two intervention villages using World Health Organization (WHO) susceptibility test kits. Additional mechanisms contributing to observed phenotypic resistance were investigated using Centers for Disease Control (CDC) bottle bioassays with piperonylbutoxide (PBO) and S,S,S-tributyl phosphorotrithioate (DEF) synergists. Resistance genotyping for kdr and Ace-1 alleles was conducted using quantitative polymerase chain reaction (qPCR). In both study villages, high phenotypic resistance to several pyrethroids and DDT was observed, with mortality in the range of 12-23%. There was a sharp decrease in mortality in An. gambiae s.l. exposed to bendiocarb (carbamate) from 84% in November 2011 to 31% in December 2012 after two rounds of bendiocarb-based indoor residual spraying (IRS). Anopheles gambiae s.l. remained susceptible to pirimiphos-methyl (organophosphate). Bendiocarb-based IRS did not lead to the reversion of pyrethroid resistance. There was no evidence for selection for Ace-1 resistance alleles. The need to investigate the operational impact of the observed resistance selection on the effectiveness of longlasting insecticidal nets and IRS for malaria control is urgent.

Keywords: Ace-1; bendiocarb; bioassays; carbamate; kdr; mutation; organophosphate; synergists.

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Figures

Figure 1
Figure 1
The map of Muleba District, in northwest Tanzania, showing the study sites at Kiteme and Kyamyorwa villages.
Figure 2
Figure 2
Trends in the resistance status of Anopheles gambiae s.l. populations in the two villages exposed to bendiocarb and lambdacyhalothrin in May and November in 2011 and 2012. No susceptibility tests were conducted in the village supplied with longlasting insecticidal nets (LLINs) in May 2011. IRS, indoor residual spraying.
Figure 3
Figure 3
Percentage knock‐down over time for an F1 generation of wild‐caught mosquitoes exposed to permethrin alone, permethrin + piperonylbutoxide (PBO), permethrin + S,S,S‐tributyl phosphorotrithioate (DEF), and permethrin + PBO + DEF relative to a permethrin test of a susceptible mosquito strain (Kisumu) in Centers for Disease Control (CDC) bottle bioassays.
See this image and copyright information in PMC

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