Insecticide resistance and activation of the metabolic detoxification enzymes of female Culex pipiens pallens by the blood meal were assessed using a micro-application bioassay and micro-plate enzyme activity assays. Four group of Cx. pipiens pallens were used, a susceptible non-engorging group at seven days after emerging, SNE7 Cp; a resistant non-engorging group at seven days after emerging, RNE7 Cp; a resistant engorged group at one day after blood feeding and a resistant engorged group at seven days after blood feeding, REG7 Cp. Insecticide resistance of Cx. pipiens pallans was increased by the blood feeding. Based on LC50 values, SNE7 Cp demonstrated >50 fold of higher susceptibility to all tested insecticides when compared with RNE7 Cp. RNE7 Cp showed higher susceptibility to all tested insecticides than REG1 Cp and REG7 Cp with a relative susceptibility LC50 (SRLC50) of 25.8 to 50.0 and 25.0 to 48.8. In micro-plate enzyme assays, the metabolic detoxification enzyme activity of Cx. pipiens pallans adult females was increased by the blood feeding. Activation of non-specific esterases (EST), glutathione-S-transferase (GST) and mixed function oxidase (MFO) in RNE7 were higher than in SNE7 and the all tested enzymes in REG1 and REG7 demonstrated significantly higher enzyme activation than RNE7, except for activation of GST in REG1. Activation of MFO in REG1 and REG7 were 209.4- and 74.6- fold higher than in REG7, respectively. Non-specific esterases (EST) and glutathione-S-transferase exhibited < 10 fold of higher Rr values. These results may be significant in terms of the criteria that are used to evaluate resistance, because blood fed female mosquitoes may show enhanced expression of the resistance phenotype, possibly allowing for earlier detection of insecticide resistance.

• Kyu-Sik Chang(Div. of Medical Entomology, Center for immunology and pathology, National Institute of Health)
• Dae-Hyun Yoo(Div. of Medical Entomology, Center for immunology and pathology, National Institute of Health)
• Seong Yoon Kim(Div. of Medical Entomology, Center for immunology and pathology, National Institute of Health)
• Mi Yeoun Park(Div. of Medical Entomology, Center for immunology and pathology, National Institute of Health)
• E-Hyun Shin(Div. of Medical Entomology, Center for immunology and pathology, National Institute of Health)
• Wook-Gyo Lee(Div. of Medical Entomology, Center for immunology and pathology, National Institute of Health)
• Jong Yul Roh(Div. of Medical Entomology, Center for immunology and pathology, National Institute of Health)