Abstract
BackgroundMosquitoes have developed resistance against pyrethroids, the only class of insecticides approved for use on long-lasting insecticidal nets (LLINs). The present study sought to evaluate the efficacy of the pyrethroid synergist PermaNet® 3.0 LLIN versus the pyrethroid-only PermaNet® 2.0 LLIN, in an East African hut design in Lower Moshi, northern Tanzania. In this setting, resistance to pyrethroid insecticides has been identified in Anopheles gambiae mosquitoes.MethodsStandard World Health Organization bioefficacy evaluations were conducted in both laboratory and experimental huts. Experimental hut evaluations were conducted in an area where there was presence of a population of highly pyrethroid-resistant An. arabiensis mosquitoes. All nets used were subjected to cone bioassays and then to experimental hut trials. Mosquito mortality, blood-feeding inhibition and personal protection rate were compared between untreated nets, unwashed LLINs and LLINs that were washed 20 times.ResultsBoth washed and unwashed PermaNet® 2.0 and PermaNet® 3.0 LLINs had knockdown and mortality rates of 100% against a susceptible strain of An. gambiae sensu stricto. The adjusted mortality rate of the wild mosquito population after use of the unwashed PermaNet® 3.0 and PermaNet® 2.0 nets was found to be higher than after use of the washed PermaNet® 2.0 and PermaNet® 3.0 nets.ConclusionsGiven the increasing incidence of pyrethroid resistance in An. gambiae mosquitoes in Tanzania, we recommend that consideration is given to its distribution in areas with pyrethroid-resistant malaria vectors within the framework of a national insecticide-resistance management plan.
Highlights
Mosquitoes have developed resistance against pyrethroids, the only class of insecticides approved for use on long-lasting insecticidal nets (LLINs)
This study demonstrated that both unwashed LLINs and LLINs washed 20 times provided a high personal protection against An. arabiensis mosquitoes, which were found to be pyrethroid-tolerant according to the criteria provided by the World Health Organization (WHO) protocol for susceptibility test
The present study reveals that the use of both unwashed and washed PermaNet® 2.0 LLINs was associated with higher mortality rates than with the PermaNet® 3.0 LLINs
Summary
Mosquitoes have developed resistance against pyrethroids, the only class of insecticides approved for use on long-lasting insecticidal nets (LLINs). The present study sought to evaluate the efficacy of the pyrethroid synergist PermaNet® 3.0 LLIN versus the pyrethroid-only PermaNet® 2.0 LLIN, in an East African hut design in Lower Moshi, northern Tanzania In this setting, resistance to pyrethroid insecticides has been identified in Anopheles gambiae mosquitoes. Combined insecticides have reduced the level of resistance in the vector population [15], and rotating insecticides periodically has shown to be effective against wild vector populations or in delaying the build-up of insecticides resistance among vectors [11, 15, 16] None of these options are able to reduce the metabolic activity of the mosquito against insecticides. Discovering a tool that can reduce or inhibit the enzymatic activity of the mosquitoes against classes of insecticides is a top priority to curb the resistance problem
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