Multimodal platform for ITN efficacy: Surface chemistry, bioavailability, and mosquito behavior.

Area of Science:

• Environmental chemistry
• Vector control
• Materials science

Background:

• Insecticide-treated nets (ITNs) are vital for malaria control but face challenges from mosquito resistance.
• Per- and polyfluoroalkyl substances (PFAS) are used in ITN coatings, but their environmental impact is a concern.
• Understanding the role of PFAS in ITN efficacy is crucial for developing sustainable malaria control strategies.

Purpose of the Study:

• To investigate the impact of removing PFAS from ITN coatings on the bio-efficacy against malaria vectors.
• To analyze the chemical and physical changes in insecticide formulations after PFAS removal.
• To assess the behavioral responses of malaria vectors to PFAS-free ITNs.

Main Methods:

• Multidisciplinary framework combining chemical analysis and behavioral assays.
• Surface characterization of deltamethrin particulates on PFAS-based and PFAS-free nets.
• Bio-efficacy testing against resistant malaria vectors in East and West Africa.
• Behavioral assays to measure mosquito contact time, insecticide uptake, irritancy, and knockdown.

Main Results:

• PFAS-free pyrethroid nets demonstrated reduced bio-efficacy against resistant malaria vectors compared to PFAS-based nets.
• Surface analysis revealed PFAS stabilizes smaller, noncrystalline deltamethrin, enhancing bioavailability, while PFAS-free coatings led to larger, crystalline aggregates.
• Behavioral assays indicated reduced mosquito contact time and insecticide uptake with PFAS-free formulations, especially in resistant strains.

Conclusions:

• PFAS removal from ITN coatings negatively impacts insecticide bio-availability and bio-efficacy against resistant malaria vectors.
• The findings highlight a trade-off between environmental goals (PFAS removal) and ITN effectiveness.
• A multidisciplinary approach is essential for optimizing ITN formulations for sustained malaria control and environmental safety.