Bio-efficacy of LifeNet, a deltamethrin incorporated long-lasting insecticidal net, as assessed in experimental huts against Anopheles fluviatilis, a major malaria vector in east-central India

Abstract

LifeNet, a deltamethrin incorporated long-lasting insecticidal (polypropylene) net (LLIN), was qualified by the World Health Organization Pesticide Evaluation Scheme (WHOPES) for Phase-II trial in India. The purpose of this trial was to assess the bio-efficacy of unwashed and 20 and 30 times washed LifeNet in comparison to the nets conventionally treated with deltamethrin against the natural population of Anopheles fluviatilis, a major malaria vector, in terms of deterring hut entry, inhibiting blood feeding, inducing exophily and causing mortality. The trial was carried out in six experimental huts constructed at Kandhaguda village in Malkangiri district, Odisha State. The efficacy of unwashed and washed (20 or 30 times) LifeNet was compared with untreated polypropylene and conventionally treated (with deltamethrin) polyester net washed to just before exhaustion or washed 20 times. The study showed a significant reduction of entry (treatment: 1.61–4.78; control: 7.61 per hut) and an increase in exit (50.7–64.4% and 39.1%) of An. fluviatilis in the treated arms compared to the control arm (untreated net) (P < 0.05). Blood feeding rates reduced in treated arms (20.7–68.0%) compared to the control (80.3%) (P < 0.05). Total mortality was significantly higher in LifeNet arms (73.8–98.3%) than the control (2.2%) (P < 0.05). After 30 washes, the active ingredient (AI) retention in LifeNet was 62%. Performance of the three LifeNet arms against the susceptible population of An. fluviatilis met the WHO efficacy criteria of Phase II evaluation for LLINs.