PYRETHROID-SPRAYED TENTS FOR MALARIA CONTROL - AN ENTOMOLOGICAL EVALUATION IN PAKISTAN

Field trials were undertaken in the North West Frontier Province of Pa kistan to determine the effects of pyrethroid-sprayed tents on feeding success, mortality and biting-rates of wild mosquitoes attracted to b ait cows confined within the tents. Under natural conditions, endophag ic mosquitoes rested only briefly in untreated tents during the night, followed by complete exodus at dawn. In tents sprayed on the interior surface with permethrin 0.5 mg/m(2) or with deltamethrin 0.03 g/m(2) the biting rate of Anopheles stephensi was reduced by about 40%; deter rency against culicines and other anophelines was much less. Mortality -rates of bloodfed mosquitoes from the treated tents were 75% An. step hensi, 65% An. subpictus but only 10% of culicines. Outer fly-sheets p rolonged the effective life of the treatment; bioassays on the sprayed inner-sheets showed that insecticidal efficacy remained high for over a year, whereas on tents without fly-sheets permethrin residual effic acy declined rapidly 20-40 weeks post-treatment. It is concluded that tent-spraying with fast-acting photostable residual pyrethroid insecti cide would probably provide effective protection against malaria trans mission for the inhabitants of tents in any part of the world where th e vector mosquitoes are endophilic and susceptible to pyrethroids.