Abstract
BackgroundInsecticide resistance poses a major threat to current vector control campaigns. Insecticides with novel modes of action are therefore in high demand. Pyriproxyfen (PPF), a conventional mosquito pupacide, has a unique mode of action that also sterilises adult mosquitoes (unable to produce viable offspring) upon direct contact. However, the timing of PPF exposure in relation to when mosquitoes take a blood meal has an important impact on that sterilisation. This study investigated the relationship between different blood feeding and PPF exposure timings to determine the potential of PPF sterilisation in controlling Anopheles arabiensis.MethodsFour treatment regimens were investigated: blood fed three days before PPF exposure (A), blood fed one day before PPF exposure (B), blood fed one day after PPF exposure (C) and blood fed three days after PPF exposure (D) for their impact on egg laying (fecundity) and the production of viable offspring (fertility), while the impact of PPF exposure on mosquito survival was investigated in the absence of a blood meal. All regimens and the survival study exposed mosquitoes to PPF via the bottle assay at 3 mg AI/m2 for 30 minutes.ResultsFemale mosquitoes that blood-fed one day prior to PPF exposure (regimen B), produced no viable offspring during that gonotrophic cycle (100% reduction in fertility). All other treatments had no significant effect. The observed reductions in fecundity and fertility were caused by the retention of eggs (97% of eggs retained, i.e. produced in the ovaries but not laid, in regimen B, p = 0.0004). Some of these retained eggs were deformed in shape. PPF exposure on mosquito survival in the absence of a blood meal was found to have no effect.ConclusionsThe results presented here suggest that sterilising adult malaria vectors using PPF could form part of a malaria control strategy, taking advantage of the lack of reported resistance to PPF in mosquitoes and its unique mode of action. We propose that targeting resting mosquitoes, which are highly susceptible to PPF at low doses, is the optimal direction for developing this control tool.
Highlights
Insecticide resistance poses a major threat to current vector control campaigns
It was more meaningful to conduct a single analysis of the total reduction in offspring as the number of eggs laid was close to zero for regimen B
The number of larvae that hatched from each mosquito batch was used as a measure of offspring production to determine any differences after PPF exposure
Summary
Insecticide resistance poses a major threat to current vector control campaigns. Insecticides with novel modes of action are in high demand. Pyrethroids are the only class of insecticide recommended for treatment of LLINs, while four insecticide classes These behavioural traits are thought to pose one of the greatest threats to current malaria control programs [11]. Resistance to PPF has been reported in whiteflies, which are heavily targeted agricultural pests [17,18], but there is no record of resistance in any other insect to date This and its novel impacts on adult mosquitoes make it a good candidate for combining with other insecticides for vector control [19,20]
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