Insecticides Resistance And Its Underlying Mechanisms For Dengue Vectors Ae Albopictus And Ae.Aegypti In Jinghong City,Yunnan Province

Jinghong is a border city located in the far south of Yunnan province,China.The main dengue vectors,Aedes aegypti and Ae.albopictus,thrive in this district.In recent years,due to the increasing number of foreign imported dengue cases and the high density of Aedes mosquito,Jinghong has become one of the hot spots of dengue fever in China.In 2013,the first large scale outbreak of dengue fever in Jinghong resulted in 1269 cases.A similar scale of dengue epidemic occurred again in 2015,with 1054 cases.ULV and residual spray with pyrethroids were extensively used for dengue vectors control.However,the performance of these insecticides wasn’t satisfying.This study was carried out to provide guidance in the control of dengue vector mosquitoes.The geographic distribution and habitats of dengue vectors in Jinghong was investigated,and the resistance level of four classes of commonly used insecticides as well as biorational larvicides and its underlying mechanisms was tested.The results of this study were summarized as following:1.Ae.aegypti is the dominant species in the urban areas of Jinghong City,which plays an important role in dengue virus transmission in the epidemics.This species was mainly breeding in vases,buckets,tanks,pickle jars,tyres,water dispenser trough and other idle water container.Ae,albopictus was relatively few and mainly distributed in the surrounding areas of Jinghong city.2.Aedes mosquitoes from Jinghong were highly resistant to pyrethroids,but were relatively sensitive to organophosphate,carbamate and biorational insecticides.To pyrethroids,RRs of Ae.aegypti and albopictus larvae were 12.2-865.5 and 41.6-1559.7 folds.For adults,the RRs were 36.4-336.0 and 5.0-45.2 folds.To the other three classes of insecticides,RRs of Ae.aegypti and albopictus larvae were 0.8～20.4 and 0.5-5.3 folds.For adult,the mortality under the discriminate dose was(84.44～97.96)%and(51.85～100.00)%.3.Biochemical assays revealed that the enzyme activity of MFO and GST in the wild Ae.aegypti larvae was 89.57 and 2.56 folds higher than ICDC-SUS.For adults,the ratio were 1.12 and 1.70 folds.In Ae.albopictus,the enzyme activities of GST larvae was 1.34 folds higher than JS-SUS.For adults,12.11-fold MFO activity was observed.While the synergist assays with PBO did not show a recovery of the susceptibility of Ae.aegypti to deltamethrin,the elevated susceptibility was observed in Ae.albopictus,which suggested that P450s was related to the resistance of Ae.albopictus.4.AS-PCR successfully detected V1016G(100%)and F1534C(30.4%)mutations in the wild Ae.aegypti population of Jinghong.And 11532T(23.2%)and F1534S/L(29.6%)mutations were observed in Ae.albopictus by sequenced the sodium channel gene directly.Ae.aegypti and Ae.albopictus populations from Jinghong have exhibited a significant increased resistance to pyrethroids.Insecticides with different mode of action should be recommended to use alternatively to improve the effectiveness of mosquito control and delay the development of insecticides resistance.Moreover,metabolic resistance and target resistance are involved in the high resistance against pyrethroids in Aedes populations from Jinghong.Metabolic enzymes and kdr mutations involved should be considered as parts of surveillance of vector resistance for integrated vector control and resistance management.