The impact of hotspot-targeted interventions on malaria transmission: study protocol for a cluster-randomized controlled trial

Abstract

Background: Malaria transmission is highly heterogeneous in most settings, resulting in the formation of recognizable malaria hotspots. Targeting these hotspots might represent a highly efficacious way of controlling or eliminating malaria if the hotspots fuel malaria transmission to the wider community.

Methods/design: Hotspots of malaria will be determined based on spatial patterns in age-adjusted prevalence and density of antibodies against malaria antigens apical membrane antigen-1 and merozoite surface protein-1. The community effect of interventions targeted at these hotspots will be determined. The intervention will comprise larviciding, focal screening and treatment of the human population, distribution of long-lasting insecticide-treated nets and indoor residual spraying. The impact of the intervention will be determined inside and up to 500 m outside the targeted hotspots by PCR-based parasite prevalence in cross-sectional surveys, malaria morbidity by passive case detection in selected facilities and entomological monitoring of larval and adult Anopheles populations.

Discussion: This study aims to provide direct evidence for a community effect of hotspot-targeted interventions. The trial is powered to detect large effects on malaria transmission in the context of ongoing malaria interventions. Follow-up studies will be needed to determine the effect of individual components of the interventions and the cost-effectiveness of a hotspot-targeted approach, where savings made by reducing the number of compounds that need to receive interventions should outweigh the costs of hotspot-detection.

Trial registration: NCT01575613. The protocol was registered online on 20 March 2012; the first community was randomized on 26 March 2012.

Figure 1

Overview map of one block in the study area comprising 20 cells. A map of a 2 × 2.5 km section of the study area that comprises 20 500 × 500 m cells and 80 sub-cells. Cell numbers are given in black bold letters; grey crosses indicate structures; green circles with black crosses indicate selected and numbered households. Rivers and roads are indicated in the map as given in the legend.

Figure 2

Simulation of intervention outcome. The figure presents a simulation of hotspot-targeted interventions in areas with a baseline parasite prevalence of 10% or 20%. ITN coverage is assumed to be 41% across all age groups (83% in under-fives). Plotted is smoothed parasite prevalence in the total population as a function of time in years since the start of the intervention. No interventions (solid black line), hotspot-targeted increase in LLIN coverage to reach 90% effective coverage in hotspots (dashed grey line) and hotspot-targeted increase in LLIN coverage to reach 90% effective coverage in hotspots in combination with targeted IRS reaching 90% of households in hotspots (dashed black line).