The indoor use of plastic sheeting pre-impregnated with insecticide for control of malaria vectors.

OBJECTIVE To evaluate the efficacy of permethrin-treated plastic sheeting (ITPS) applied as a lining to the ceiling or walls of rooms against pyrethroid-susceptible and pyrethroid-resistant Anopheles gambiae. METHOD Overnight tests were carried out in veranda-trap experimental huts in Vallée du Kou, where two molecular forms of A. gambiae, S and M, occur. The S form is mostly pyrethroid resistant due to the kdr mechanism, and the M form is mostly kdr susceptible. A variety of ITPS covered surfaces were tested, ranging from ceiling only to all walls plus ceiling covered. RESULTS ITPS had a major effect on the mortality of mosquitoes, the proportion killed being dependent upon the surface area covered. Homozygotes for kdr resistance showed lower rates of mortality than did heterozygotes or homozygotes for susceptibility. Deterred entry of mosquitoes and inhibition of blood feeding were also correlated with surface area covered. The mode of action and efficacy of ITPS seems to bear closer resemblance to that induced by indoor residual spraying (IRS) than to that induced by insecticide-treated nets. CONCLUSIONS ITPS might be conceived as being equivalent to long-lasting or permanent IRS but without some of the operational constraints normally associated with spraying. High coverage of ITPS could potentially have a mass population effect on mosquitoes and give rise to long-term community protection against malaria. A phase III trial is justified to assess the acceptability of ITPS and its efficacy against malaria.