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Mosquito repellents for malaria prevention

Maia, Marta F, Kliner, Merav, Richardson, Martha, Lengeler, Christian and Moore, Sarah J (2018) 'Mosquito repellents for malaria prevention'. Cochrane Database of Systematic Reviews, Issue 2, CD011595.

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Abstract

Background
Malaria is an important cause of illness and death across endemic regions. Considerable success against malaria has been achieved within the past decade mainly through long-lasting insecticide-treated nets (LLINs). However, elimination of the disease is proving difficult as current control methods do not protect against mosquitoes biting outdoors and when people are active. Repellents may provide a personal protection solution during these times.
Objectives
To assess the impact of topical repellents, insecticide-treated clothing, and spatial repellents on malaria transmission.
Search methods
We searched the following databases up to 26 June 2017: the Cochrane Infectious Diseases Group Specialized Register; the Central Register of Controlled Trials (CENTRAL), published in the Cochrane Library; MEDLINE; Embase; US AFPMB; CAB Abstracts; and LILACS. We also searched trial registration platforms and conference proceedings; and contacted organizations and companies for ongoing and unpublished trials.
Selection criteria
We included randomized controlled trials (RCTs) and cluster-randomized controlled trials of topical repellents proven to repel mosquitoes; permethrin-treated clothing; and spatial repellents such as mosquito coils. We included trials that investigated the use of repellents with or without LLINs, referred to as insecticide-treated nets.
Data collection and analysis
Two review authors independently reviewed trials for inclusion, extracted the data, and assessed the risk of bias. A third review author resolved any discrepancies. We analysed data by conducting meta-analysis and stratified by whether the trials had included LLINs. We combined results from cRCTs with individually RCTs by adjusting for clustering and presented results using forest plots. We used GRADE to assess the certainty of the evidence.
Main results
Eight cRCTs and two RCTs met the inclusion criteria. Six trials investigated topical repellents, two trials investigated insecticide-treated clothing, and two trials investigated spatial repellents.
Topical repellents
Six RCTS, five of them cluster-randomized, investigated topical repellents involving residents of malaria-endemic regions. Four trials used topical repellents in combination with nets, but two trials undertaken in displaced populations used topical repellents alone. It is unclear if topical repellents can prevent clinical malaria (RR 0.65, 95% CI 0.4 to 1.07, very low certainty evidence) or malaria infection (RR 0.84, 95% CI 0.64 to 1.12, low-certainty evidence) caused by P. falciparum. It is also unclear if there is any protection against clinical cases of P. vivax (RR 1.32, 95% CI 0.99 to 1.76, low-certainty evidence) or incidence of infections (RR 1.07, 95% CI 0.80 to 1.41, low-certainty evidence). Subgroup analysis of trials including insecticide-treated nets did not show a protective effect of topical repellents against malaria. Only two studies did not include insecticide-treated nets, and they measured different outcomes; one reported a protective effect against clinical cases of P. falciparum (RR 0.40, 95% CI 0.23 to 0.71); but the other study measured no protective effect against malaria infection incidence caused by either P. falciparum or P. vivax.

Insecticide-treated clothing
Insecticide-treated clothing were investigated in trials conducted in refugee camps in Pakistan and amongst military based in the Colombian Amazon. Neither study provided participants with insecticide-treated nets. In the absence of nets, treated clothing may reduce the incidence of clinical malaria caused by P. falciparum by approximately 50% (RR 0.49, 95% CI 0.29 to 0.83, low-certainty evidence) and P. vivax (RR 0.64, 95% CI 0.40 to 1.01, low-certainty evidence).

Spatial repellents
Two cluster-randomized RCTs investigated mosquito coils for malaria prevention. We do not know the effect of spatial repellents on malaria prevention (RR 0.24, 95% CI 0.03 to 1.72, very low certainty evidence). There was large heterogeneity between studies and one study had high risk of bias.
Authors' conclusions
There is insufficient evidence to conclude topical or spatial repellents can prevent malaria. There is a need for better designed trials to generate higher certainty of evidence before well-informed recommendations can be made. Adherence to daily compliance remains a major limitation. Insecticide-treated clothing may reduce risk of malaria infection in the absence of insecticide-treated nets; further studies on insecticide-treated clothing in the general population should be done to broaden the applicability of the results.

Item Type: Article
Subjects: QS Anatomy > QS 4 General works. Classify here works on regional anatomy
WA Public Health > Preventive Medicine > WA 108 Preventive health services. Preventive medicine. Travel Medicine.
WA Public Health > Preventive Medicine > WA 110 Prevention and control of communicable diseases. Transmission of infectious diseases
WA Public Health > Preventive Medicine > WA 240 Disinfection. Disinfestation. Pesticides (including diseases caused by)
WC Communicable Diseases > Tropical and Parasitic Diseases > WC 750 Malaria
Faculty: Department: Clinical Sciences & International Health > Clinical Sciences Department
Digital Object Identifer (DOI): https://doi.org/10.1002/14651858.CD011595.pub2
Depositing User: Stacy Murtagh
Date Deposited: 13 Feb 2018 10:51
Last Modified: 27 Jun 2018 10:11
URI: https://archive.lstmed.ac.uk/id/eprint/8232

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