title: Co-occurrence of point mutations in the voltage-gated sodium channel of pyrethroid-resistant Aedes aegypti populations in Myanmar.
abstract: BACKGROUND
  Single amino acid substitutions in the voltage-gated sodium channel associated with pyrethroid resistance constitute one of the main causative factors of knockdown resistance in insects. The kdr gene has been observed in several mosquito species; however, point mutations in the para gene of Aedes aegypti populations in Myanmar have not been fully characterized. The aim of the present study was to determine the types and frequencies of mutations in the para gene of Aedes aegypti collected from used tires in Yangon City, Myanmar.
  
  
  RESULTS
  We determined high pyrethroid resistance in Aedes aegypti larvae at all collection sites in Yangon City, by using a simplified knockdown bioassay. We showed that V1016G and S989P mutations were widely distributed, with high frequencies (84.4% and 78.8%, respectively). By contrast, we were unable to detect I1011M (or I1011V) or L1014F mutations. F1534C mutations were also widely distributed, but with a lower frequency than the V1016G mutation (21.2%). High percentage of co-occurrence of the homozygous V1016G/S989P mutations was detected (65.7%). Additionally, co-occurrence of homozygous V1016G/F1534C mutations (2.9%) and homozygous V1016G/F1534C/S989P mutations (0.98%) were detected in the present study.
  
  
  CONCLUSIONS
  Pyrethroid insecticides were first used for malaria control in 1992, and have since been constantly used in Myanmar. This intensive use may explain the strong selection pressure toward Aedes aegypti, because this mosquito is generally a domestic and endophagic species with a preference for indoor breeding. Extensive use of DDT for malaria control before the use of this chemical was banned may also explain the development of pyrethroid resistance in Aedes aegypti.
authors: Department of Vector Ecology and Environment, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan.
authors: Hitoshi
authors: H
authors: Kawada
authors: Department of Vector Ecology and Environment, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan; Medical Entomology Research Division, Department of Medical Research (Lower Myanmar), Yangon, Myanmar.
authors: Sai Zaw Min
authors: SZ
authors: Oo
authors: Medical Entomology Research Division, Department of Medical Research (Lower Myanmar), Yangon, Myanmar.
authors: Sein
authors: S
authors: Thaung
authors: Department of Vector Ecology and Environment, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan.
authors: Emiko
authors: E
authors: Kawashima
authors: Medical Entomology Research Division, Department of Medical Research (Lower Myanmar), Yangon, Myanmar.
authors: Yan Naung Maung
authors: YN
authors: Maung
authors: Medical Entomology Research Division, Department of Medical Research (Lower Myanmar), Yangon, Myanmar.
authors: Hlaing Myat
authors: HM
authors: Thu
authors: Medical Entomology Research Division, Department of Medical Research (Lower Myanmar), Yangon, Myanmar.
authors: Kyaw Zin
authors: KZ
authors: Thant
authors: Department of Vector Ecology and Environment, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan; The Global Center of Excellence Program, Nagasaki University, Nagasaki, Japan.
authors: Noboru
authors: N
authors: Minakawa
mesh_terms: D000330:Aedes / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics; D019943:Amino Acid Substitution; D000818:Animals; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology*; D007814:Larva / Q000187:drug effects; D008969:Molecular Sequence Data; D002052:Myanmar; D017354:Point Mutation; D011722:Pyrethrins / Q000494:pharmacology*; D017422:Sequence Analysis, DNA; D061566:Voltage-Gated Sodium Channels / Q000235:genetics*
chemical_list: D007306:Insecticides; D011722:Pyrethrins; D061566:Voltage-Gated Sodium Channels