Randomised Control Trial: Uganda

Background:

In 2023, of the 597,000 deaths attributed to malaria globally, 95 percent occurred
in Africa. Uganda had the third highest global burden of malaria cases (4.8
percent) and the tenth highest level of deaths (2.7 percent). Progress towards
malaria elimination is threatened by challenges including insecticide resistance, and
limitations in coverage of existing vector control tools due to increasing costs.
Spatial repellents reduce human–vector contact by repelling the vector, making
the host more difficult for the vector to locate and inhibiting biting. Repellents
provide protection against biting in enclosed, semi-enclosed and peri-domestic
spaces. Some existing spatial repellent devices require a source of external power or
heat to diffuse and disperse the volatile active ingredients; however, many houses
in sub-Saharan Africa have limited or no access to electricity. The Mossie-GO — a
solar-powered device that actively distributes the insect repellent transfluthrin
through a non-heat fan system — provides an alternative to traditional electricity-
powered devices.

Project outline and objectives:

The project partners carried out a cluster-randomised placebo-controlled trial in Jinja and Buikwe districts, eastern Uganda. The trial evaluated the protective efficacy of Mossie-GO in children under five years of age living in areas of moderate to high malaria transmission.

The Mossie-GO is a solar-powered device fitted with coin refills impregnated with the repellent transfluthrin and a carrier oil. The coins, which need to be replaced every month, sit above a small fan that distributes the repellent around the room to kill mosquitoes. The device is attached to a solar cell unit that must be placed in direct sunlight to charge during the day for use in the evening and overnight.

A total of 56 clusters of households were randomly assigned to one of two study arms, to receive either the repellent device or a placebo device containing blank discs with no active ingredient. Households have been asked to continue using other malaria prevention practices, such as mosquito nets, as recommended by national policy.

The the impact of the device in reducing the prevalence of malaria infection in children ≤5 years of age was measured alongside, entomological factors linked to disease transmission, including vector densities, biting rates and host-seeking behaviour.

Activities:

Trained village health teams distributed 9,431 Mossie-GO devices to households in both Buikwe and Jinja districts. They returned at monthly intervals to provide sustained protection. Households in the control arm
received blank discs with no active ingredient. Trained research assistants monitored recruited households
at six-monthly intervals. Children under five years were tested for malaria over a period of 12 months. Every six months, vector populations were monitored: indoor light traps ran overnight to collect mosquitoes in selected households, and human landing catches — when people sit with their lower legs exposed and collect the mosquitoes that come to feed on them — were conducted inside and outside households. Air
sampling was carried out to determine concentrations of transfluthrin in the air. An acceptability survey and a household survey to collect information on participants’ behaviour related to malaria exposure and their use of existing control tools was also conducted.

Outcomes and impact:

Providing evidence of the efficacy and acceptability of the Mossie-GO spatial repellent in preventing malaria in children under five in a real-world setting. The evidence generated from this study will be shared with policy makers in Uganda and other countries, to inform the choice of suitable vector control
measures.

Addressing health inequalities by broadening the range of malaria prevention measures that can be used by households that lack access to a reliable power source. Adding an effective intervention to the vector control toolbox that can be used alongside existing measures would ultimately help to reduce
morbidity and mortality from malaria.