Durable wall lining for malaria control in Liberia: results of a cluster randomized trial

Abstract

BackgroundMalaria control in Liberia depends upon universal coverage with pyrethroid-impregnated long-lasting insecticidal nets (LLINs). Despite regular mass distribution, LLIN coverage and usage is patchy. Pyrethroid resistance in malaria vectors may further reduce LLIN efficacy. Durable Wall Lining (DWL), a novel material treated with two non-pyrethroid class insecticides, was designed to be installed onto the surface of inner walls, and cover openings and ceiling surfaces of rural houses.ObjectivesAimTo determine the malaria control efficacy of DWL.Primary objectiveTo determine if DWL has an additional protective effect in an area of pyrethroid resistance.Secondary objectivesTo compare surface bio-availability of insecticides and entomological effectiveness over the study duration.DesignA cluster randomized trial.ParticipantsChildren aged 2–59 months.Control arm50 houses per 20 clusters, all of which received LLIN within the previous 12 months.Active arm50 houses per 20 experimental clusters, all of which received LLINs with the previous 12 months, and had internal walls and ceilings lined with DWL.RandomisationCluster villages were randomly allocated to control or active arms, and paired on 4 covariates.Main outcome measuresPrimary measurePrevalence of infection with P. falciparum in children aged 2 to 59 months.Secondary measureSurface bioavailability and entomological effectiveness of DWL active ingredients.ResultsPlasmodium falciparum prevalence in active clusters after 12 months was 34.6% compared to 40.1% in control clusters (p = 0.052). The effect varied with elevation and was significant (RR = 1.3, p = 0.022) in 14 pairs of upland villages. It was not significant (RR = 1.3, p = 0.344) in 6 pairs of coastal villages. Pooled risk ratio (RR) was calculated in SAS (Cary, NC, USA) using the Cochran–Mantel–Haenszel (CMH) test for upland and coastal cluster pairs. DWL efficacy was sustained at almost 100% for 12 months.ConclusionsFindings indicate that DWL is a scalable and effective malaria control intervention in stable transmission areas with pyrethroid-resistant vectors, where LLIN usage is difficult to achieve, and where local housing designs include large gable and eve openings.Trial registration ClinicalTrials.gov identifier: NCT02448745 (19 May 2015): https://clinicaltrials.gov/ct2/show/NCT02448745