MAALEM-Btmosquito: A Novel Floating Granular Bti Formulation for Aedes aegypti Control in Domestic Water-Storage Containers

Integrated management of Aedes aegypti, the primary urban vector of dengue, Zika, and chikungunya, requires effective, environmentally safe larvicides with sufficient residual activity for operational use. We developed and evaluated MAALEM-Btmosquito, a novel floating granular formulation based on Bacillus thuringiensis subsp. israelensis (Bti), designed to maintain larvicidal activity under routine water use and partial water replacement in domestic water containers. Outdoor semi-field bioassays were conducted in 20 L buckets and 200 L drums under three water-replacement regimes (0%, 10%, and 50%). Groups of 25 late third- and early fourth-instar Ae. aegypti larvae were exposed at successive post-treatment intervals, and mortality was assessed at 24 and 48 h over 30 days. MAALEM-Btmosquito caused 100% mortality at 24 h on the first day and maintained >94.5% larval mortality throughout the study. Overall mean 24 h mortality across treatments was 98.8%, with treatment means ranging from 94.7% (95% CI, 91.9–96.5) to 99.7% (95% CI, 98.5–99.9). The greatest reduction in activity was observed in 20 L containers subjected to 50% water replacement. Operational performance was evaluated during three application cycles involving more than 700 households in Puente de Ixtla, Morelos, Mexico. The Breteau Index decreased by 72.6%, 64.6%, and 81.1%, while the mean egg count per ovitrap decreased from 93.2 ± 76.10 before the first MAALEM-Btmosquito application to 25.4 ± 20.44 eggs after completion of the field interventions. Because the community evaluation was conducted without a concurrent untreated control area, these field observations are associative and cannot be attributed solely to MAALEM-Btmosquito. Potential confounding factors include seasonality, rainfall, other vector-control activities, and household water-use behavior. Together with the controlled semi-field results, these findings support the potential of MAALEM-Btmosquito as a larvicide for integrated mosquito vector management.