Genomic surveillance of mosquito resistance to guide cost-effective insecticide policy in Rwanda

Abstract

In Rwanda, mosquito control interventions, relying on bed nets and insecticide spraying on household walls, remain dominant in malaria prevention. Insecticides, widely used in both public health and agriculture, are becoming less effective across the country. Resistance data collected between 2022 and 2023 showed a clear geographic distribution of insecticide resistance in mosquitoes. In seven districts, Anopheles gambiae collected during both rainy and dry seasons were tested with WHO tube assays. Pre-exposure to piperonyl butoxide (PBO) as a pyrethroid synergist significantly increased mortality after pyrethroid exposure. Still, mortality did not reach 98-100%, indicating the presence of additional resistance mechanisms, including target-site resistance, glutathione S-transferases and esterases, cuticular resistance, and behavioral resistance. These findings demonstrate that a uniform insecticide deployment plan is no longer sufficient. This policy brief recommends enhancing insecticide resistance management through routine vector molecular surveillance tools and genomic surveillance, expanding resistance monitoring to twice yearly at sentinel sites, prioritizing PBO-treated nets in high-resistance areas, and rotating alternative non-pyrethroid insecticides where appropriate.