Abstract
BACKGROUND AND AIM: In The Gambia, malaria transmission persists due to insecticide resistance and residual vector behavior, despite extensive use of indoor residual spraying and insecticide-treated nets. Community-led larval source management using Bacillus thuringiensis var. israelensis (Bti) offers a sustainable vector control alternative. This study aimed to assess the effectiveness and feasibility of community-led Bti application for reducing Anopheles mosquito populations, compared to expert-supervised application and non-intervention control arms. MATERIALS AND METHODS: A non-randomized controlled trial was conducted across malaria-endemic regions in The Gambia from 2023 to 2024. Intervention arms included: (1) community-led Bti application, (2) expert-supervised Bti application, and (3) untreated control. Trained volunteers and entomologists applied Bti to breeding sites at weekly or biweekly intervals. Entomological surveys were conducted biweekly to monitor larval, pupal, and adult mosquito densities. Data were analyzed using generalized linear mixed models and negative binomial regression, adjusting for environmental covariates. RESULTS: By round 10, community-led and expert-supervised interventions achieved 96.8% and 98.6% reductions in larval density, 97.4% and 99.1% reductions in pupal emergence, and 96.2% and 98.8% reductions in adult mosquito populations, respectively. Statistically significant declines in mosquito densities were observed by 2024 (p < 0.001). Community participation enabled high coverage and operational sustainability, with over 85% of participants reporting visible mosquito reduction. CONCLUSIONS: Seasonal Bti application, especially when led by trained community members, significantly suppresses Anopheles populations. Although expert-supervised methods yielded slightly higher efficacy, community-led biolarviciding offers a scalable, sustainable, and environmentally safe vector control strategy, supporting The Gambia's malaria elimination goals.