Optimizing the impact of a novel spatial repellent on malaria incidence in Western Kenya

Progress in reducing global malaria incidence has slowed in recent years, demonstrating the need for new vector control tools to complement existing interventions in reaching global malaria control targets. Spatial repellents (SRs) are a promising new product class that are intended to reduce pathogen transmission by altering the host-seeking and/or feeding behaviors of Anopheles spp. mosquito vectors. A recent cluster-randomized control trial conducted in a high malaria burden area of weatenLKenm found that SRs reduced the hazard rate of first-time malaria infection by 33.4% in a setting with substantial insecticide resistance and high coverage of insecticide treated nets. We modeled the likely impact of the SR intervention in this setting under different deployment strategies, with the goal of identifying the best overall and per-product strategies. Continuous monthly SR deployment with 100% coverage caused the greatest (45.1%) reduction in infections versus no SR, although some non-continuous seasonal approaches averted more infections per SR product. Six months of SR use with 100% coverage starting in October caused a 36.4% reduction in infections while using only half as many products, and eight months starting in September reduced infections by 44.7%. This study identified optimum and efficient SR use strategies and highlights the importance of SR protection during periods of low and increasing transmission, particularly in October and November during the short rainy season. These findings can be used to develop vector and disease control strategies that warrant field testing for validation. When resources are limited, the coverage, deployment strategy, and timing of SR deployment all play a key role in maximizing product impact.