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

ABSTRACT: BACKGROUND:Insecticides 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. RESULTS:With 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. CONCLUSIONS:Our 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.

SUBMITTER: Thievent K

PROVIDER: S-EPMC5936035 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature

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

Thiévent Kevin K Hofer Lorenz L Rapp Elise E Tambwe Mgeni Mohamed MM Moore Sarah S Koella Jacob C JC

Parasites & vectors 20180504 1

<h4>Background</h4>Insecticides 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 ( ...[more]

PMID: 29728155

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Project description:BACKGROUND:Protecting people outdoors against mosquito-borne diseases is a major challenge. Here we compared commercially available personal protection methods to identify the most effective method for outdoor use in northern Lao PDR. METHODS:From June to August 2016 the protective efficacy of treatments were compared in a secondary forest during the afternoon and a village during the evening. Comparisons were made using a replicated Latin square design between: (i) short permethrin-treated overalls; (ii) long permethrin-treated overalls; (iii) short untreated overalls with para-menthane-3,8-diol (PMD) applied topically; (iv) short permethrin-treated overalls plus PMD applied topically; (v) short untreated overalls with metofluthrin coils in a metal casing worn on a belt; and (vi) long untreated overalls. Short untreated overalls served as the control. Cone tests were conducted on the treated and untreated fabric before and after field experiments. A questionnaire survey was used to measure social acceptability. RESULTS:Mosquito coils in a metal casing worn on a belt resulted in 92.3% (95% confidence interval, CI: 88.9-94.6%). landing protection from female mosquitoes in the afternoon and 68.8% (95% CI: 41.7-83.3%) protection in the evening compared to short untreated clothing. PMD was protective both when combined with short permethrin-treated overalls (afternoon, 68.2%, 95% CI: 52.6-78.7%; evening, 52.3%, 95% CI: 33.8-65.7%) and when used in combination with short untreated overalls (afternoon, 55.0%, 95% CI: 41.7-65.2%; evening, 25.2%, 95% CI: 9.4-38.2%). Whilst long permethrin-treated overalls were protective (afternoon, 61.1%, 95% CI: 51.4-68.8%; evening, 43.0%, 95% CI: 25.5-56.4%), short permethrin-treated overalls and long untreated overalls were not. Exposure to new permethrin-treated fabric in cone tests resulted in 25.0% (95% CI, 17.8-32.2%) and 26.2% (95% CI 16.7-35.8%) mortality for susceptible Ae. albopictus and susceptible Ae. aegypti, respectively. There was a loss of efficacy of permethrin-treated clothing after use in the field, with 3 min knockdown rates of Ae. albopictus and 1 h knockdown of Ae. aegypti decreasing over time. Participants considered all treatments acceptable. CONCLUSIONS:The portable mosquito coils were highly protective against outdoor biting mosquitoes, although there are safety concerns related to its use. The combination of permethrin-treated clothing and PMD repellent represent an alternative treatment for protection against outdoor-biting mosquitoes.

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

Publications

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

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