Slow release pyrethroid-impregnated indoor linings as a new malaria vector control method

摘要

Background: Indoor Residual Spraying (IRS) and Long-Lasting Insecticide-Treated Nets (LLINs) are the most effective malaria vector control methods. The organochloride pesticide, DDT, is still used for IRS and can retain its efficacy for up to twelve months. However, research indicated that harmful levels of DDT residues are present in indoor air for up to three months after spraying. LLINs only provide protection if people sleep under the net. Certain polymers with insecticide embedded in the fibre can be used as slow release carriers for vector control, possibly becoming a long term substitute for IRS. Aims: To assess the efficacy, durability and community acceptability and perceived efficiency of pyrethroid-impregnated linings in community homes in Limpopo province, South Africa, over a six month period. Methods:A field trial is currently taking place in the community village of Tshilivho in Vhembe district, Limpopo. Forty households (20 mud huts and 20 brick houses) are included. Monofilament polyethylene meshing with one of two deltamethrin-, one of two α-cypermethrin concentrations, or no insecticide were attached along the inside wall of one sleeping hut or room per household. Data on acceptability is gathered with questionnaires, and lining samples are tested bi-monthly for efficacy according to WHO recommended bioassays. Results: The linings yielded positive results in initial laboratory bioassays from field samples collected up to date. Test mosquitoes were exposed for 30 minutes to field samples, resulting in 100% knockdown (KD) within this time. Within 24 hours 100% mortality was noted. Preliminary questionnaire data show that the linings are killing mosquitoes on contact and also less biting is reported. Conclusions:Preliminary results indicate that the use of these pyrethroid-impregnated indoor linings is potentially as successful as IRS. This new and potentially safe method might be a more sustainable approach for vector control. Acknowledgements: The study is supported by the University of Pretoria Centre for Sustainable Malaria Control.