Pyrethroid-impregnated hessian curtains for protection against mosquitoes indoors in south India

Hessian curtains impregnated with deltamethrin 50 mg/m2 were hung in the eaves and doorways of eight one-roomed huts in Madurai, Tamil Nadu State, South India. Statistically significant reductions of indoor-resting and man-biting densities of the mosquitoes Anopheles subpictus and Culex quinquefasciatus were observed for 14 weeks, in two field trials. Bioassays on curtains in the field showed over 50% mortality of Cx quinquefasciatus and An.stephensi for up to 8 weeks. The curtains were highly acceptable to the community, and cost approximately Rs.33.15 (US$1.05) for material and Rs.10 ($0.32) for delta-methrin per hut, totalling Rs 53.15 ($1.70) for two impregnations giving 6 months protection. Comparative costs of house-spraying with residual insecticides are estimated as Rs.1.92 ($0.06) for two rounds of DDT at 1 g/m2, or Rs.40 ($1.27) for three rounds of malathion at 2 g/m2. Therefore the relative annual cost of protection using deltamethrin-impregnated hessian curtains is 28 x or 1.3 x more than for house-spraying with DDT or malathion, respectively (excluding operational expenditure).