Impact of permethrin-treated bed nets on entomologic indices in an area of intense year-round malaria transmission.
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 Anopheles gambiae s.l. and An. funestus in intervention houses were 58.5% (P = 0.010) and 94.5% (P = 0.001) lower, respectively, compared with control houses. The sporozoite infection rate in An. gambiae s.l. was 0.8% in intervention areas compared with 3.4% (P = 0.026) in control areas, while the sporozoite infection rates in An. funestus were not significantly different between the two areas. We estimated the overall transmission of Plasmodium falciparum 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 An. gambiae s.l., 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.
Division of Parasitic Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30341, USA.
John E
JE
Gimnig
John M
JM
Vulule
Terrence Q
TQ
Lo
Luna
L
Kamau
Margarette S
MS
Kolczak
Penelope A
PA
Phillips-Howard
Evan M
EM
Mathenge
Feiko O
FO
ter Kuile
Bernard L
BL
Nahlen
Allen W
AW
Hightower
William A
WA
Hawley
D000818:Animals; D000852:Anopheles / Q000469:parasitology; D001512:Bedding and Linens; D006801:Humans; D007303:Insect Vectors; D007306:Insecticides / Q000494:pharmacology*; D007630:Kenya / Q000453:epidemiology; D016778:Malaria, Falciparum / Q000453:epidemiology / Q000517:prevention & control*; D026023:Permethrin / Q000494:pharmacology*; D010963:Plasmodium falciparum; D011156:Population Density; D012621:Seasons
D007306:Insecticides; D026023:Permethrin