ABSTRACT
[Abstract] Objective To explore the role of metabolic detoxification enzyme activity and knockdown resistance (kdr) gene mutations in the pyrethroid resistance of Aedes (Ae.) albopictus. Methods From Aug. to Sep. in 2017, the Ae. albopictus samples were collected in Qianfoshan Park, Jinan City, Shandong Province (JN), Shangmaojiabu, Hangzhou City, Zhejiang Province (HZ), Baoshan Sixth Village, Baoshan District, Shanghai (BS), Gongqing Forest Park, Yangpu District, Shanghai (YP), and Meilan District Residential Area, Haikou City, Hainan Province (HK). The above five field populations were all resistant to insecticide. The activities of metabolic detoxification enzymes (glutathione-S transferase [GST] and mixed function oxidase [MFO]) were detected and compared with the Ae. albopictus susceptible strain (JS). The contribution rates of activity changes of GST and MFO and kdr mutations (I1532 and F1534) in the resistance formation were analyzed by the classification and regression trees (CART). Results The baseline enzyme activities of GST and MFO in Ae. albopictus JS were both significantly higher than those in the BS and HK resistant populations (both P0.01). There were no significant difference in the activities of GST and MFO between the BS population unexposed and exposed to deltamethrin (P0.05). After exposure to permethrin of BS population, the activities of GST and MFO were significantly increased (P0.05, P0.01). After exposure to deltamethrin, the GST activity was not significantly changed in the HK population (P0.05), while the MFO activity was significantly increased (P0.01). However, after exposure to permethrin in the HK population, there were no significant changes in the GST and MFO activities (both P0.05). In the 5 field resistant populations exposed to deltamethrin and permethrin, the changes of GST and MFO activities were irregular compared with baseline of Ae. albopictus JS strain. CART analysis showed that in the resistance formation of Ae. albopictus against deltamethrin, the contribution rates of GST activity and kdr F1534 mutation were the greatest, followed by MFO activity, and the kdr I1532 mutation was the smallest. In the resistance formation of Ae. albopictus against permethrin, the kdr F1534 mutation had the highest contribution rate, followed by the GST and MFO activities, and the kdr I1532 mutation had no contribution. Conclusion The activity levels of metabolic detoxification enzymes (GST and MFO) are not suitable as single markers for detecting the resistance of Ae. albopictus to pyrethroids. The activity changes of metabolic detoxification enzymes and kdr mutations may be two synergistic mechanisms in the resistance formation of Ae. albopictus to pyrethroid insecticides.