The Preliminary Study On Kdr Mediated Repellent Behavior And Mechanism

Background:Aedes albopictus can transmit a variety of arboviral diseases through blood feeding,which seriously threatens human health.At present,the control of mosquitoes still relies on insecticides,but the long-term and large-scale use of insecticides leads to the development of mosquito resistance,which brings new challenges to the strategies of disease control.In some studies,pyrethroids have been found to have repellent effects on mosquitoes in addition to killing them,which can cause changes in mosquito behavior.When mosquitoes develop target resistance to insecticides,mutations of kdr genotype can be detected in the VGSC gene.Some studies have reported that the susceptible mosquitoes showed obvious repellent behavior under sublethal concentrations of insecticides,but the insensitivity of mosquitoes with kdr mutation to insecticides would lead to a decrease in repellent behavior,which could enable them to locate the host and then cause disease transmission.However,the exact mechanism of mosquito repellent behavior remains unclear.Therefore,understanding the change and mechanism of kdr mediated repellent behavior in mosquitoes is significant for disease control strategies.Objective:In this study,deltamethrin resistant strains of Aedes albopictus were established and those with homozygous kdr mutation at locus 1532 or 1534 were constructed.The susceptible strain and deltamethrin resistant strains above of Aedes albopictus were used as the research objects,to explore the repellent behavior and mechanism of mosquitoes to pyrethroid insecticides under the participation of kdr.Methods:1.The kdr genotype of deltamethrin resistant Lab-R30 was detected.The kdr 1532 locus homozygous mutation strain R30-1532T and the kdr 1534 locus homozygous mutation strain R30-1534S with the same genetic background as Lab-R30 were established by selection or hybridization;2.The spatial activity index(SAI)and repellency percentage were used to evaluate the repellent response of mosquitoes.By studying the repellent behaviors of deltamethrin,bioallethrin,transfluthrin and DEET in susceptible and resistant strains,discuss the effects of kdr on(1):changes in the repellent behavior of mosquitoes;(2):the difference of repellent response of mosquitoes to different drugs;3.Evaluate the plasticity of repellent behavior of different mosquitoes to different insecticides by exposing mosquitoes to the same pyrethroid insecticides repeatedly within a day,and explore the mechanism that may play a dominant role in this phenomenon.Results:1.Deltamethrin resistant strains R30-1532T and R30-1534S with homozygous mutation at locus 1532 or 1534 on VGSC were successfully constructed;2.Compared with the susceptible strain,the resistant strains showed significantly decreased repellent behaviors to deltamethrin,bioallethrin and transfluthrin,but no significant difference in repellent behaviors to DEET;3.Compared with the susceptible strain,the olfactory deficient Orco▲ strain showed a significant decrease in the repellent behavior to bioallethrin and DEET,but no significant difference in the repellent behavior to deltamethrin and transfluthrin;4.There were dose effect relations between the repellent behavior of susceptible and resistant strains of Aedes albopictus to deltamethrin,bioallethrin and transfluthrin;5.Both susceptible strain Lab-S and resistant strain Lab-R30 showed plasticity of repellent behavior to bioallethrin and transfluthrin;The homozygous mutation strain R30-1532T at locus 1532 only showed plasticity of repellent behavior to transfluthrin;The homozygous mutation strain R30-1534S at locus 1534 showed plasticity of repellent behavior to both deltamethrin and bioallethrin.Conclusion:1.The repellent behaviors of resistant mosquitoes with kdr selected by deltamethrin were significantly decreased under the sublethal concentrations of deltamethrin,and the repellent behaviors to bioallethrin and transfluthrin were also significantly decreased,among which the homozygous mutation at 1534 locus contributed the most to the decrease in repellent behavior of mosquitoes;2.When mosquitoes were repeatedly exposed to sublethal concentrations of pyrethroid insecticides in a short period of time,susceptible and resistant mosquitoes had different plasticity of repellent behavior.The homozygous mutation at kdr 1532 locus was mainly associated with the repellent behavioral plasticity of transfluthrin,and the homozygous mutation at kdr 1534 locus was mainly associated with the repellent behavioral plasticity of deltamethrin and bioallethrin.When mosquitoes with kdr mutation are exposed to sublethal concentrations of pyrethroid insecticides,the significant decrease in repellent behavior and the plasticity of repellent behavior in the short term would lead to a decrease in the proportion of mosquitoes flying away from the host,and then promote the transmission of diseases.