title: 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.
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.
authors.affiliation: Department of Medical Parasitology and Entomology, Kilimanjaro Christian Medical University College, Moshi, Tanzania; Pan-African Malaria Vector Research Consortium (PAMVERC), Moshi, Tanzania.
authors.forename: J
authors.initials: J
authors.lastname: Matowo
authors.forename: J
authors.initials: J
authors.lastname: Kitau
authors.forename: R
authors.initials: R
authors.lastname: Kaaya
authors.forename: R
authors.initials: R
authors.lastname: Kavishe
authors.forename: A
authors.initials: A
authors.lastname: Wright
authors.forename: W
authors.initials: W
authors.lastname: Kisinza
authors.forename: I
authors.initials: I
authors.lastname: Kleinschmidt
authors.forename: F
authors.initials: F
authors.lastname: Mosha
authors.forename: M
authors.initials: M
authors.lastname: Rowland
authors.forename: N
authors.initials: N
authors.lastname: Protopopoff
mesh_terms: D000818:Animals; D000852:Anopheles / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D003634:DDT / Q000494:pharmacology*; D005260:Female; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology*; D009032:Mosquito Control / Q000379:methods*; D057147:Mosquito Nets; D011722:Pyrethrins / Q000494:pharmacology*; D012621:Seasons; D013636:Tanzania
chemical_list: D019476:Insect Proteins; D007306:Insecticides; D011722:Pyrethrins; D003634:DDT
keywords: Ace-1; bendiocarb; bioassays; carbamate; kdr; mutation; organophosphate; synergists