title: First identification of kdr allele F1534S in VGSC gene and its association with resistance to pyrethroid insecticides in Aedes albopictus populations from Haikou City, Hainan Island, China.
abstract: BACKGROUND
  Aedes albopictus is distributed widely in China, as a primary vector of Dengue fever and Chikungunya fever in south of China. Chemical insecticide control is one of the integrated programmes to prevent mosquito-borne diseases. Long-term applications of pyrethroids have resulted in the development of resistance in Ae. albopictus populations in China. However, the susceptibility of Ae. albopictus to pyrethroids in Hainan Island was unclear. Knockdown resistance (kdr), caused by point mutations in the VGSC gene, is one of the mechanisms that confer resistance to DDT and pyrethroids. This study was to investigate the resistance level of Ae. albopictus populations in Haikou City to three pyrethroid insecticides, and elucidate the relationship between the resistant phenotype and kdr mutations.
  
  
  METHODS
  The Aedes albopictus samples were collected in Xinbu Island (XI), Longtang Town (LT), Shishan Town (ST), Baishamen Park (BP), and Flower Market (FM) from Haikou City, Hainan Island, China. The larval susceptibility to deltamethrin, permethrin and beta-cypermethrin was tested by larval bioassays, and adult susceptibility to deltamethrin and DDT was determined by adult bioassays. The degree of resistance was determined by resistance ratio value (RR50 > 3) for larvae and by mortality for adult. The kdr alleles at codon 1534 of the VGSC gene were genotyped. The relationship between kdr genotypes and resistant phenotypes was analyzed by Chi-square test.
  
  
  RESULTS
  Out of five populations, assessed by larval bioassays, XI was susceptible to deltamethrin and permethrin; LT was susceptible to permethrin and beta-cypermethrin; and ST was susceptible to permithrin. FM and BP both were resistant to all of the three pyrethroids, and FM showed the highest degree of resistance, with RR50 values from 65.17 to 436.36. A total of 493 individuals from the larval bioassays were genotyped for kdr alleles. Five alleles were detected, including two wildtype alleles, TTC(F) (67.04 %) and TTT(F) (0.41 %), and three mutant alleles, TGC(C) (0.30 %), TCC(S) (31.54 %) and TTG(L) (0.71 %). There was a clear correlation between mutant alleles (or F1534S) and resistant phenotypes (P < 0.01).
  
  
  CONCLUSIONS
  Two novel kdr mutant alleles F1534S and F1534L were detected in the pyrethroid resistant populations of Ae. albopictus in Haikou Hainan, China. For the first time, the mutant F1534S was associated with pyrethroid resistance in Ae. albopictus.
authors.affiliation: Department of Tropical Infectious Diseases, Faculty of Tropical Medicine and Public Health, Second Military Medical University, Shanghai, 200433, China.
authors.forename: Huiying
authors.initials: H
authors.lastname: Chen
authors.affiliation: Department of Tropical Infectious Diseases, Faculty of Tropical Medicine and Public Health, Second Military Medical University, Shanghai, 200433, China.
authors.forename: Kaili
authors.initials: K
authors.lastname: Li
authors.affiliation: Haikou Center for Disease Control and Prevention, Haikou, 571100, China.|CDC Key Laboratory of Surveillance and Early-Warning on Infectious Disease, Haikou, 571100, China.
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Wang
authors.affiliation: Haikou Center for Disease Control and Prevention, Haikou, 571100, China.|CDC Key Laboratory of Surveillance and Early-Warning on Infectious Disease, Haikou, 571100, China.
authors.forename: Xinyan
authors.initials: X
authors.lastname: Yang
authors.affiliation: Haikou Center for Disease Control and Prevention, Haikou, 571100, China.|CDC Key Laboratory of Surveillance and Early-Warning on Infectious Disease, Haikou, 571100, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Lin
authors.affiliation: Haikou Center for Disease Control and Prevention, Haikou, 571100, China.|CDC Key Laboratory of Surveillance and Early-Warning on Infectious Disease, Haikou, 571100, China.
authors.forename: Fang
authors.initials: F
authors.lastname: Cai
authors.affiliation: Haikou Center for Disease Control and Prevention, Haikou, 571100, China.|CDC Key Laboratory of Surveillance and Early-Warning on Infectious Disease, Haikou, 571100, China.
authors.forename: Wenbin
authors.initials: W
authors.lastname: Zhong
authors.affiliation: Haikou Center for Disease Control and Prevention, Haikou, 571100, China.|CDC Key Laboratory of Surveillance and Early-Warning on Infectious Disease, Haikou, 571100, China.
authors.forename: Chunyan
authors.initials: C
authors.lastname: Lin
authors.affiliation: Haikou Center for Disease Control and Prevention, Haikou, 571100, China.|CDC Key Laboratory of Surveillance and Early-Warning on Infectious Disease, Haikou, 571100, China.
authors.forename: Zhongling
authors.initials: Z
authors.lastname: Lin
authors.affiliation: Department of Tropical Infectious Diseases, Faculty of Tropical Medicine and Public Health, Second Military Medical University, Shanghai, 200433, China. yajun_ma@163.com.|CDC Key Laboratory of Surveillance and Early-Warning on Infectious Disease, Haikou, 571100, China. yajun_ma@163.com.
authors.forename: Yajun
authors.initials: Y
authors.lastname: Ma
mesh_terms: D000330:Aedes / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D000483:Alleles; D000818:Animals; D002681:China; D005260:Female; D019476:Insect Proteins / Q000235:genetics* / Q000378:metabolism; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology*; D062312:Islands; D007814:Larva / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D008297:Male; D020125:Mutation, Missense; D011722:Pyrethrins / Q000494:pharmacology*; D061566:Voltage-Gated Sodium Channels / Q000235:genetics* / Q000378:metabolism
chemical_list: D019476:Insect Proteins; D007306:Insecticides; D011722:Pyrethrins; D061566:Voltage-Gated Sodium Channels
keywords: Aedes albopictus; China; Pyrethroids; Resistance; kdr mutation