Walter van Pareen

The World Health Organization (WHO) is promoting the use of insecticide treated nets (ITNs) in order to roll back malaria. Long-life netting (LLIN) is preferred and this study investigated the possibility of incorporating the insecticide in the fiber polymer. Multifilament polypropylene (PP) yarn, containing up to 0.76% of pyrethroid insecticide, was successfully produced on a conventional production-scale fiber-spinning machine. The insecticides were incorporated via masterbatches that contained up to 18.8% active with low-density polyethylene (LDPE) as the carrier. Nets knitted from the yarns were tested using bioassays with mosquitoes. Initial efficacy complied with WHO specifications but the performance deteriorated with the number of wash cycles. Crystalline insecticides, featuring a melting point above the wash temperature of 60°C (e.g., β-cyfluthrin), provided better wash resistance than amorphous insecticides (e.g., cyfluthrin).