Evaluation of the Protective Efficacy of a Spatial Repellent to Reduce Malaria Prevalence in Uganda

Overview

A cluster-randomized double-blinded control trial will be conducted in Uganda to demonstrate and quantify the protective efficacy (PE) of Mossie-GO, an active spatial repellent system disseminating transfluthrin, in reducing the prevalence of malaria in children ≤ 5 years of age, as determined by RDT positivity and confirmed by microscopy. The study's secondary objective is to measure the diversionary impact of the intervention on locally unprotected individuals and impact of the intervention on entomological correlates of transmission including vector densities, host seeking behaviour and insecticide resistance. This will be conducted using Centre of Disease Control (CDC) light traps in households, human landing catches and World Health Organisation (WHO) tube tests. Further data collection include household behavioural surveys, air sampling to quantify concentration of transfluthrin present in air, acceptability surveys and intervention safety monitoring. Recruited households will be monitored across baseline data collection and followed up for 2 disease transmission seasons, for up to 18 months. The devices will be distributed to all consented eligible households in the two study arms: intervention and control. Intervention arm devices will be provided with transfluthrin treated discs and refill transfluthrin discs at frequent enough intervals to provide sustained protection. Households in the control arm will receive blank discs with no active ingredient. Households will be asked to continue using other malaria prevention practices, such as the use of bed nets, as recommended by national policy.

The impact of Mossie-GO on malaria cases will be determined through a blinded cluster randomized trial in malaria endemic settings. The device will be distributed to all consented eligible households in the two study arms: intervention and control. Intervention arm devices will be provided with transfluthrin treated discs and refill transfluthrin discs at frequent enough intervals to provide sustained protection. Households in the control arm will receive blank discs with no active ingredient and refill blank discs to maintain study blinding. The Mossie-GO repellent device is approximately 8 cm3 and can be fitted with repellent discs impregnated with transfluthrin and a carrier oil. These discs sit above a fan that is powered by a small motor charged by solar energy. The device is expected to both prevent bites and cause some mortality to mosquitoes when switched on for 8-12 hours overnight for up to 1 calendar month. The discs then need to be replaced. One Mossie-GO device will be provided per household, along with a solar cell unit that will be connected to the Mossie-GO unit and must be placed in direct sunlight to charge the Mossie-Go unit during the day, for use in the evening. Households will be asked to continue using other malaria prevention practices, such as bed nets, as recommended by national policy. At baseline, Mossie-GO will be distributed at the household level and should be placed in the room of the participant enrolled into the study (child ≤ 5 years of age) while they are sleeping. At the same time a baseline survey will be conducted and children ≤ 5 years of age will be tested for malaria using RDTs and microscopy, to determine baseline malaria prevalence. At this time, household surveys will also be conducted to classify housing structure and collect other variables which may impact the efficacy of the intervention. Following this period, sample size estimates may be adjusted based on malaria prevalence. All recruited households will be monitored at 6-monthly intervals and malaria testing will be done among children ≤ 5 years of age with RDTs and microscopy over a period of up to 18 months. Indoor light traps will be installed in selected households for approximately 3-4 nights in the 6 month intervals and run from 6pm to 7 am to collect mosquitoes indoors, and human landing catches will be conducted. Air sampling will also be conducted alongside mosquito collections to quantify the concentrations of transfluthrin in the air and to help inform entomological and epidemiological outcomes. An acceptability survey will also be conducted at the final data collection time point The unit of randomization is a cluster, which is defined as a discrete village or area containing a minimum of 100 households. Clusters will be divided into core and buffer zones. Twenty eight clusters will be identified per study arm (treatment and control), thus fifty six clusters will be selected in total. Households within the core zone of clusters will receive the Mossie-GO device (intervention or control). Households within the buffer zones will not receive the Mossie-GO. While all households within the core zone of the cluster are receiving the device, they will not all be sampled for the evaluation of the primary objective (PE). Only a total of 100 eligible, consenting households will be sampled within the core zones. Household surveys will also be conducted in these 100 households. For the evaluation of the secondary outcomes, a subset of houses will be selected. Diversionary impact: 100 households in buffer zone; entomological sampling: 10% of households in core zone; air sampling 1 household every 500m in core zone. The primary outcome (PE) will be compared between arms using logistic regression with a random effect for study cluster and adverse event data will be collected and summarised.