Malaria infection in mosquitoes decreases the personal protection offered by permethrin-treated bednets

Abstract

BackgroundInsecticides targeting adult mosquitoes are the main way of controlling malaria. They work not only by killing mosquitoes, but also by repelling and irritating them. Indeed their repellent action gives valuable personal protection against biting mosquitoes. In the context of malaria control this personal protection is especially relevant when mosquitoes are infectious, whereas to protect the community we would prefer that the mosquitoes that are not yet infectious are killed (so, not repelled) by the insecticide. As the infectious stage of malaria parasites increases the motivation of mosquitoes to bite, we predicted that it would also change their behavioural response to insecticides.ResultsWith two systems, a laboratory isolate of the rodent malaria Plasmodium berghei infecting Anopheles gambiae and several isolates of P. falciparum obtained from schoolchildren in Tanzania that infected Anopheles arabiensis, we found that mosquitoes harbouring the infectious stage (the sporozoites) of the parasite were less repelled by permethrin-treated nets than uninfected ones.ConclusionsOur results suggest that, at least in the laboratory, malaria infection decreases the personal protection offered by insecticide-treated nets at the stage where the personal protection is most valuable. Further studies must investigate whether these results hold true in the field and whether the less effective personal protection can be balanced by increased community protection.Electronic supplementary materialThe online version of this article (10.1186/s13071-018-2846-0) contains supplementary material, which is available to authorized users.

Impact of Insecticide Resistance on P. falciparum Vectors’ Biting, Feeding, and Resting Behaviour in Selected Clusters in Teso North and South Subcounties in Busia County, Western Kenya

“…Journal of Parasitology Research bitten and infected frequently [30,31]. The interference with preference and frequency by a female mosquito to bite noninfected persons and or animals over infected persons may be a game changer as far as decline in active malaria transmission cases is concerned.…”

The role of insecticides and malaria infection on the mosquito’s behaviour and the consequences for malaria transmission

“…Indeed, with a laboratory setting, we recently showed that partially resistant A. arabiensis mosquitoes infected with Plasmodium falciparum sporozoites (the stages of the human malaria parasite that are infectious for human) were no more repelled by permethrin-treated nets [89]. Thus, it suggests that the combination of resistance and malaria infection in mosquitoes may drastically reduce the personal protection ITNs may offer.…”

“…Unfortunately, since sporozoites make mosquitoes more motivated to bite [51][52][53][54][55], we might expect that they are less irritated by the insecticide. Indeed, we found in a laboratory experiment that infectious mosquitoes (carrying sporozoites) were less repelled by ITNs [89].…”

“…We detected the sporozoites with a PCR of the head and thorax of 21-day old mosquitoes as described by Thiévent and coworkers [89].…”

“…DNA extraction of mosquito salivary glands was obtained with a slightly modified DNAzol© procedure [89]. 125 µl DNAzol© were added to the 9 µl of salivary homogenate, then the mix was vortexed and incubated for 20 minutes at 55 C°.…”