Laboratory evaluation of a new alphacypermethrin long-lasting insecticidal net against Anopheles culicifacies s.l.

Abstract

Long-lasting insecticidal nets (LLINs) are being promoted by World Health Organization (WHO) as key vector control tool for the prevention and control of malaria and other vector-borne diseases. A laboratory study was conducted to evaluate the bio-efficacy of a new alphacypermethrin LN (HILNET®) against insecticide-susceptible Anopheles culicifacies s.l.. This study presents the observations on (a) regeneration time, the period required to regenerate insecticide in the LLIN after three consecutive WHO standard washes in a single day to deplete the insecticide on the net surface, and (b) wash resistance of the LLIN to retain bio-efficacy up to 20 repeated washes at intervals corresponding to the regeneration time in days. In the present evaluation, the regeneration time of HILNet® was determined as 2days. Wash resistance studies of HILNet® showed a knockdown rate of 100% up to 15 washes and 97% at the 20th wash and complied with the criteria of WHO knockdown rate of ≥ 95%. The mean active ingredient content from 0 to 20 washes was in the range of 5.8 to 6.04g/kg and met the WHO criteria of the product claim (± 25% g/kg). The insecticide un-impregnated control net has shown no detectable levels of alphacypermethrin. In this evaluation, HILNet® fulfilled the WHO laboratory (phase I) efficacy criteria based on the rates of knockdown up to 20 standard WHO washes.