EVALUATION OF PERMETHRIN-TREATED MILITARY UNIFORMS FOR PERSONAL PROTECTION AGAINST MALARIA IN NORTHEASTERN THAILAND

A trial to compare the effect of military clothing treated by high-pre ssure spray with permethrin or placebo on the incidence of malaria in Royal Thai Army troops was conducted in northeastern Thailand. Bioassa ys of treated clothing using laboratory-reared Anopheles dirus females showed permethrin remained in the treated fabric for up to 90 days. B oth permethrin- and placebo-treated uniform shirts provided >84% prote ction from biting An. dirus in laboratory bioassays for the duration o f the study. In laboratory tests, knockdown of An. dirus exposed to pe rmethrin-treated cloth fell to <20% after 3 hand washes, despite the p resence of 28.7-59.9% of the original dose of permethrin. The use of p ermethrin-treated uniforms without adjunct application of topical repe llents did not reduce malaria in Thai troops in an operational setting where incidence during 6 months was as high as 412 cases/1,000 in spi te of chemoprophylaxis and use of untreated bednets.