Current status of insecticide resistance and its underlying mechanisms in Aedes aegypti (L.) in Punjab, Pakistan

Aedes aegypti (Linnaeus) plays an important role as a vector of different deadly diseases particularly dengue fever. Insecticides are used as a primary tool to control Ae. aegypti. However, due to the excessive use of insecticides on agricultural, public health, and industrial levels, mosquitoes have developed resistance. In this study, the current susceptibility status of Ae. aegypti mosquitoes against different insecticides (Temephos, DDT, dieldrin, Malathion, Bendiocarb, Permethrin, Cypermethrin, and Lambda-cyhalothrin) was evaluated in district Lahore and district Muzaffargarh of Punjab, Pakistan. For this purpose, WHO bioassays and biochemical assays were performed on Ae. aegypti population from Lahore (APLa) and Aedes population from Muzaffargarh (APMg). Results of APLa and APMg showed high levels of resistance against the larvicide Temephos. Resistance against all adulticides was also observed in APLa and APMg (% mortality < 98%). The biochemical assays indicated statistically significant elevated levels of detoxification enzymes in APLa and APMg. APLa showed slightly higher levels as compared to APMg. Mosquitoes were also screened for the presence of kdr mutations. The results revealed no mutation in domain II while the presence of mutation F1534C in domain III was found in both field populations. The results showed the presence of moderate to high grade resistance against all insecticides in Ae. aegypti in district Lahore and district Muzaffargarh of Punjab, Pakistan

Role of metabolic detoxification enzyme activity and knockdown resistance gene mutations in resistance of aedes albopictus to pyrethroid insecticides / 第二军医大学学报

[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.

The classification of esterases: an important gene family involved in insecticide resistance - A review

The use of chemical insecticides continues to play a major role in the control of disease vector populations, which is leading to the global dissemination of insecticide resistance. A greater capacity to detoxify insecticides, due to an increase in the expression or activity of three major enzyme families, also known as metabolic resistance, is one major resistance mechanisms. The esterase family of enzymes hydrolyse ester bonds, which are present in a wide range of insecticides; therefore, these enzymes may be involved in resistance to the main chemicals employed in control programs. Historically, insecticide resistance has driven research on insect esterases and schemes for their classification. Currently, several different nomenclatures are used to describe the esterases of distinct species and a universal standard classification does not exist. The esterase gene family appears to be rapidly evolving and each insect species has a unique complement of detoxification genes with only a few orthologues across species. The examples listed in this review cover different aspects of their biochemical nature. However, they do not appear to contribute to reliably distinguish among the different resistance mechanisms. Presently, the phylogenetic criterion appears to be the best one for esterase classification. Joint genomic, biochemical and microarray studies will help unravel the classification of this complex gene family.