title: Insecticide resistance in potential vector mosquitoes for West Nile virus in Japan.
abstract: Culex pipiens complex is the significant vector mosquito of West Nile virus. To take stock of the current situation of insecticide susceptibilities and design an ideal mosquito control strategy, we collected Culex pipiens pallens Coquillet, Culex pipiens form molestus Forskal, and Culex quinquefasciatus Say from fields in Japan and conducted bioassays for five larvicides (fenitrothion, temephos, etofenprox, diflubenzuron, and pyriproxyfen) by using a larval dipping method. Among five insecticides tested, obvious reduced susceptibilities were observed for etofenprox, which is the only pyrethroid compound registered as a larvicide in Japan. Twenty-two of 56 colonies exhibited a >10% survival rate at the etofenprox concentration of 5.7 microg/ml, which is a 10 times higher concentration of the working solution. The LC50 of a colony collected from Fukuoka prefecture for etofenprox exceeded 60 microg/ml (resistance ratio >2,307), and this colony also exhibited cross-resistance to other pyrethroids, permethrin (299-fold) and phenothrin (1,200-fold). The insect growth regulators diflubenzuron and pyriproxyfen were found to be sufficiently effective enough to control Culex larvae present, but decreased sensitivities to these insecticides were slightly detected in some colonies of Cx. p. form molestus collected from urban areas. Several etofenprox-resistant colonies of Cx. p. form molestus exhibited simultaneously decreased susceptibilities to other insecticides, including temephos, diflubenzuron, and pyriproxyfen.
authors.affiliation: Department of Medical Entomology, National Institute of Infectious Diseases, Toyama, Shinjuku-ku, Tokyo 162-8640, Japan. kasacin@nih.go.jp
authors.forename: Shinji
authors.initials: S
authors.lastname: Kasai
authors.forename: Toshio
authors.initials: T
authors.lastname: Shono
authors.forename: Osamu
authors.initials: O
authors.lastname: Komagata
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Tsuda
authors.forename: Mutsuo
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Mitsugu
authors.initials: M
authors.lastname: Motoki
authors.forename: Ichiro
authors.initials: I
authors.lastname: Kashima
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Tanikawa
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yoshida
authors.forename: Ikuo
authors.initials: I
authors.lastname: Tanaka
authors.forename: Goro
authors.initials: G
authors.lastname: Shinjo
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Hashimoto
authors.forename: Takeshi
authors.initials: T
authors.lastname: Ishikawa
authors.forename: Tomoya
authors.initials: T
authors.lastname: Takahashi
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Higa
authors.forename: Takashi
authors.initials: T
authors.lastname: Tomita
mesh_terms: D000818:Animals; D003465:Culex; D007303:Insect Vectors / Q000187:drug effects*; D007305:Insecticide Resistance / Q000502:physiology*; D007306:Insecticides; D007564:Japan; D007814:Larva; D007928:Lethal Dose 50; D018675:Toxicity Tests / Q000379:methods; D014901:West Nile Fever / Q000635:transmission
chemical_list: D007306:Insecticides