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

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Abstract BackgroundControl of malaria in Liberia depends on a strategy of universal coverage of the population with pyrethroid-impregnated long-lasting insecticidal nets. Despite regular mass distribution, coverage and usage of long-lasting insecticidal nets is patchy, and pyrethroid resistance in the key malaria vectors may further reduce their efficacy. This study investigates the effectiveness of Durable Wall Lining, a novel material treated with a combination of two non-pyrethroid class insecticides, designed to be installed permanently on the surface of the inner walls, cover openings and ceiling surfaces of rural houses. MethodsA cluster randomized controlled trial of a prototype wall liner impregnated with the insecticides fenpyroximate and abamectin. In 20 experimental clusters, rooms of consenting homeowners received durable, insecticidal wall liners in addition to existing long-lasting insecticidal nets. In 20 control clusters, homeowners used only long-lasting insecticidal nets. Each experimental cluster was paired with a control cluster based on 5 covariates. Plasmodium falciparum prevalence in children 2-59 months was measured by rapid diagnostic tests before durable, insecticidal wall liner installation and again 12, 18 and 24 months later. The pooled risk ratio (RR) of P. falciparum infections was calculated in SAS (Cary, NC, USA) using the Cochran–Mantel–Haenszel (CMH) test for cluster pairs in each region within Bomi County (upland or coastal). Mosquito mortality was calculated by scoring dead and alive mosquitoes at 24 and 72 hours post exposure to DL samples and adjusting with Abbot’s formula as required.ResultsP. falciparum prevalence in intervention clusters after 12 months was 34.6% compared to 40.1% in control clusters (p=0.052), and this effect varied with elevation. Over the course of the study, malaria prevalence decreased in both study arms. ConclusionsThese findings suggest that durable, insecticidal wall liners is a scalable intervention for control of pyrethroid-resistant malaria vectors in locations where high long-lasting insecticidal nets usage is difficult to achieve, especially where local housing design includes large openings at the gables and eves. Trial registrationClinicalTrials.gov identifier: NCT02448745. Registered 19 May 2015. Available at: https://clinicaltrials.gov/ct2/show/NCT02448745

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