Effect of permethrin-impregnated nets on exiting behavior, blood feeding success, and time of feeding of malaria mosquitoes (Diptera : Culicidae) in western Kenya

The impact of permethrin-treated bednets on the feeding and house entering/ exiting behavior of malaria vectors was assessed in two studies in western Kenya. In one study, matched pairs of houses were allocated randomly to rec eive bednets or no bednets. Exiting mosquitoes were collected in Colombian curtains hung around half of each house; indoor resting mosquitoes were col lected by pyrethrum spray catches. The number of Anopheles gambiae Giles an d An. arabiensis Patton estimated to have entered the houses was unaffected by the presence of bednets; Anopheles funestus Giles was less likely to en ter a house if bednets were present. Anopheles gambiae and An. funestus wer e less likely to obtain a blood meal and. significantly more likely to exit houses when bednets were present. No difference was detected in An. arabie nsis rates of blood feeding and exiting. In a second experiment, hourly nig ht biting collections were done on 13 nights during the rainy season to ass ess whether village-wide use of permethrin-treated bednets caused a shift i n the time of biting of malaria vectors. A statistically significant shift was detected in the biting times of An. gambiae s.l., although the observed differences were small. No change was observed in the hourly distribution of An. funestus biting. Our study demonstrated that, at least in the short- term,bednets reduced human-vector contact and blood feeding success but did not lead to changes in the biting times of the malaria vectors in western Kenya.