The western Kenya insecticide-treated bed net trial
  • ISSN: 0002-9637
  • E-ISSN: 1476-1645


The effect of permethrin-treated bed nets (ITNs) on malaria vectors was studied as part of a large-scale, randomized, controlled trial in western Kenya. Indoor resting densities of fed and in intervention houses were 58.5% ( = 0.010) and 94.5% ( = 0.001) lower, respectively, compared with control houses. The sporozoite infection rate in was 0.8% in intervention areas compared with 3.4% ( = 0.026) in control areas, while the sporozoite infection rates in were not significantly different between the two areas. We estimated the overall transmission of in intervention areas to be 90% lower than in control areas. Permethrin resistance was not detected during the study period. As measured by densities of , the efficacy of bed nets decreased if one or more residents did not sleep under a net or if bed nets had not been re-treated within six months. These results indicate that ITNs are optimally effective if used every night and if permethrin is reapplied at least biannually.


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