title: Insecticide resistance of Anopheles sinensis and An. vagus in Hainan Island, a malaria-endemic area of China.
abstract: BACKGROUND
  Malaria is one of the most important public health problems in Southeast Asia, including Hainan Island, China. Vector control is the main malaria control measure, and insecticide resistance is a major concern for the effectiveness of chemical insecticide control programs. The objective of this study is to determine the resistance status of the main malaria vector species to pyrethroids and other insecticides recommended by the World Health Organization (WHO) for indoor residual sprays.
  
  
  METHODS
  The larvae and pupae of Anopheles mosquitoes were sampled from multiple sites in Hainan Island, and five sites yielded sufficient mosquitoes for insecticide susceptibility bioassays. Bioassays of female adult mosquitoes three days after emergence were conducted in the two most abundant species, Anopheles sinensis and An. vagus, using three insecticides (0.05% deltamethrin, 4% DDT, and 5% malathion) and following the WHO standard tube assay procedure. P450 monooxygenase, glutathione S-transferase and carboxylesterase activities were measured. Mutations at the knockdown resistance (kdr) gene and the ace-1 gene were detected by DNA sequencing and PCR-RFLP analysis, respectively.
  
  
  RESULTS
  An. sinensis and An. vagus were the predominant Anopheles mosquito species. An. sinensis was found to be resistant to DDT and deltamethrin. An. vagus was susceptible to deltamethrin but resistant to DDT and malathion. Low kdr mutation (L1014F) frequency (<10%) was detected in An. sinensis, but no kdr mutation was detected in An. vagus populations. Modest to high (45%-75%) ace-1 mutation frequency was found in An. sinensis populations, but no ace-1 mutation was detected in An. vagus populations. Significantly higher P450 monooxygenase and carboxylesterase activities were detected in deltamethrin-resistant An. sinensis, and significantly higher P450 monooxygenase, glutathione S-transferase and carboxylesterase activities were found in malathion-resistant An. vagus mosquitoes.
  
  
  CONCLUSIONS
  Multiple insecticide resistance was found in An. sinensis and An. vagus in Hainan Island, a malaria-endemic area of China. Cost-effective integrated vector control programs that go beyond synthetic insecticides are urgently needed.
authors.forename: Qian
authors.initials: Q
authors.lastname: Qin
authors.forename: Yiji
authors.initials: Y
authors.lastname: Li
authors.forename: Daibin
authors.initials: D
authors.lastname: Zhong
authors.forename: Ning
authors.initials: N
authors.lastname: Zhou
authors.forename: Xuelian
authors.initials: X
authors.lastname: Chang
authors.forename: Chunyuan
authors.initials: C
authors.lastname: Li
authors.forename: Liwang
authors.initials: L
authors.lastname: Cui
authors.forename: Guiyun
authors.initials: G
authors.lastname: Yan
authors.affiliation: Key Laboratory of Prevention and Control for Emerging Infectious Diseases of Guangdong Higher Education Institutes, Department of Pathogen Biology, School of Public Health and Tropical Medicine, Southern Medical University, Guangzhou, Guangdong 510515, China. xgchen2001@hotmail.com.
authors.forename: Xiao-Guang
authors.initials: XG
authors.lastname: Chen
mesh_terms: D000818:Animals; D000852:Anopheles / Q000187:drug effects* / Q000235:genetics; D001483:Base Sequence; D002681:China / Q000453:epidemiology; D019353:Endemic Diseases; D005260:Female; D006801:Humans; D019476:Insect Proteins / Q000235:genetics; D007303:Insect Vectors / Q000187:drug effects* / Q000235:genetics; D007305:Insecticide Resistance / Q000235:genetics*; D007306:Insecticides / Q000494:pharmacology; D007814:Larva; D008288:Malaria / Q000453:epidemiology / Q000517:prevention & control*; D008969:Molecular Sequence Data; D009032:Mosquito Control; D009154:Mutation; D009570:Nitriles / Q000494:pharmacology; D012150:Polymorphism, Restriction Fragment Length; D011679:Pupa; D011722:Pyrethrins / Q000494:pharmacology; D017422:Sequence Analysis, DNA
chemical_list: D019476:Insect Proteins; D007306:Insecticides; D009570:Nitriles; D011722:Pyrethrins; C017180:decamethrin