title: A small-scale field trial of pyriproxyfen-impregnated bed nets against pyrethroid-resistant Anopheles gambiae s.s. in western Kenya.
abstract: Pyrethroid resistance is becoming a major problem for vector control programs, because at present, there are few suitable chemical substitutes for pyrethroids, as when used on bed nets the insecticide must have low mammalian toxicity as well as high activity to mosquitoes. Pyriproxyfen (PPF) is one of the most active chemicals among the juvenile hormone mimic (JHM) group. Sterilizing mosquitoes by using PPF could be a potential control measure for pyrethroid-resistant malaria vectors. We investigated the sterilizing effects of two types of PPF-impregnated bed nets - a 1% PPF-impregnated net and a 1% PPF +2% permethrin-impregnated net (Olyset Duo) - to pyrethroid-resistant wild population of Anopheles gambiae s.s. in western Kenya. High mortality of blood-fed mosquitos was observed 3 days post-collection, in the houses where PPF-impregnated nets were used, indicating the effect of PPF on the longevity of mosquitos that came in contact with the net. Reduction in the number of ovipositing females, number of eggs, and number of progeny per female were also observed in the houses in which both Olyset Duo and PPF-impregnated nets were used. This is the first field study showing the high sterilizing efficacy of PPF against wild pyrethroid-resistant An. gambiae s.s. population. In addition, we recognized the necessity of combined use of permethrin with PPF, in order to reduce the risk of mosquito bites and provide a level of personal protection. Further studies on wild pyrethroid-resistant mosquito populations such as An. arabiensis and An. funestus s.s. would provide more information on the practical use of the PPF-impregnated bed nets.
authors.affiliation: Department of Vector Ecology and Environment, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Kawada
authors.affiliation: Department of Vector Ecology and Environment, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan; School of Public Health, Maseno University, Kisumu, Kenya.
authors.forename: Gabriel O
authors.initials: GO
authors.lastname: Dida
authors.affiliation: Health and Crop Sciences Research Laboratory, Sumitomo Chemical Co. Ltd., Hyogo, Japan.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Ohashi
authors.affiliation: Department of Vector Ecology and Environment, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan.
authors.forename: Emiko
authors.initials: E
authors.lastname: Kawashima
authors.affiliation: Springs of Hope, Mbita, Kenya.
authors.forename: George
authors.initials: G
authors.lastname: Sonye
authors.affiliation: Eastern and Southern Africa Centre of International Parasite Control, Nairobi, Kenya.
authors.forename: Sammy M
authors.initials: SM
authors.lastname: Njenga
authors.affiliation: Kenya Medical Research Institute, Nairobi, Kenya.
authors.forename: Charles
authors.initials: C
authors.lastname: Mwandawiro
authors.affiliation: Department of Vector Ecology and Environment, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan; The Global Center of Excellence Program, Nagasaki University, Nagasaki, Japan.
authors.forename: Noboru
authors.initials: N
authors.lastname: Minakawa
mesh_terms: D000818:Animals; D000852:Anopheles / Q000187:drug effects / Q000472:pathogenicity; D006801:Humans; D007303:Insect Vectors / Q000187:drug effects; D057148:Insecticide-Treated Bednets; D007306:Insecticides / Q000494:pharmacology*; D007605:Juvenile Hormones / Q000737:chemistry / Q000494:pharmacology; D007630:Kenya; D008288:Malaria / Q000517:prevention & control* / Q000635:transmission; D009032:Mosquito Control; D011722:Pyrethrins / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology*
chemical_list: D007306:Insecticides; D007605:Juvenile Hormones; D011722:Pyrethrins; D011725:Pyridines; C055613:pyriproxyfen