title: Insecticide resistance in malaria vectors along the Thailand-Myanmar border.
abstract: BACKGROUND
  There is a paucity of data about the susceptibility status of malaria vectors to Public Health insecticides along the Thailand-Myanmar border. This lack of data is a limitation to guide malaria vector-control in this region. The aim of this study was to assess the susceptibility status of malaria vectors to deltamethrin, permethrin and DDT and to validate a simple molecular assay for the detection of knock-down resistance (kdr) mutations in the study area.
  
  
  METHODS
  Anopheles mosquitoes were collected in four sentinel villages during August and November 2014 and July 2015 using human landing catch and cow bait collection methods. WHO susceptibility tests were carried out to measure the mortality and knock-down rates of female mosquitoes to deltamethrin (0.05%), permethrin (0.75%) and DDT (4%). DNA sequencing of a fragment of the voltage-gated sodium channel gene was carried out to identify knock-down resistance (kdr) mutations at position 1014 in mosquitoes surviving exposure to insecticides.
  
  
  RESULTS
  A total of 6295 Anopheles belonging to ten different species were bioassayed. Resistance or suspected resistance to pyrethroids was detected in An. barbirostris (s.l.) (72 and 84% mortality to deltamethrin (n = 504) and permethrin (n = 493) respectively), An. hyrcanus (s.l.) (33 and 48% mortality to deltamethrin (n = 172) and permethrin (n = 154), respectively), An. jamesii (87% mortality to deltamethrin, n = 111), An. maculatus (s.l.) (85 and 97% mortality to deltamethrin (n = 280) and permethrin (n = 264), respectively), An. minimus (s.l.) (92% mortality, n = 370) and An. vagus (75 and 95% mortality to deltamethrin (n =148) and permethrin (n = 178), respectively). Resistance or suspected resistance to DDT was detected in An. barbirostris (s.l.) (74% mortality, n = 435), An. hyrcanus (s.l.) (57% mortality, n = 91) and An. vagus (97% mortality, n = 133). The L1014S kdr mutation at both heterozygous and homozygous state was detected only in An. peditaeniatus (Hyrcanus Group).
  
  
  CONCLUSIONS
  Resistance to pyrethroids is present along the Thailand-Myanmar border, and it represents a threat for malaria vector control. Further investigations are needed to better understand the molecular basis of insecticide resistance in malaria vectors in this area.
authors.affiliation: Centre hospitalier universitaire de Montpellier, Montpellier, France. victor@shoklo-unit.com.|Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle, Institut de Recherche pour le Développement, Montpellier, France. victor@shoklo-unit.com.|Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand. victor@shoklo-unit.com.|Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand. victor@shoklo-unit.com.
authors.forename: Victor
authors.initials: V
authors.lastname: Chaumeau
authors.affiliation: Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand.
authors.forename: Dominique
authors.initials: D
authors.lastname: Cerqueira
authors.affiliation: Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand.
authors.forename: John
authors.initials: J
authors.lastname: Zadrozny
authors.affiliation: Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand.
authors.forename: Praphan
authors.initials: P
authors.lastname: Kittiphanakun
authors.affiliation: Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand.|Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK.
authors.forename: Chiara
authors.initials: C
authors.lastname: Andolina
authors.affiliation: Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand.
authors.forename: Theeraphap
authors.initials: T
authors.lastname: Chareonviriyaphap
authors.affiliation: Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand.|Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK.
authors.forename: François
authors.initials: F
authors.lastname: Nosten
authors.affiliation: Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle, Institut de Recherche pour le Développement, Montpellier, France. vincent.corbel@ird.fr.|Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand. vincent.corbel@ird.fr.
authors.forename: Vincent
authors.initials: V
authors.lastname: Corbel
mesh_terms: D063147:Animal Distribution; D000818:Animals; D000852:Anopheles / Q000187:drug effects*; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology*; D008288:Malaria / Q000635:transmission*; D002052:Myanmar / Q000453:epidemiology; D013785:Thailand / Q000453:epidemiology
chemical_list: D007306:Insecticides
keywords: Anopheles; Insecticide resistance; Malaria; Pyrethroids; Southeast Asia; Thailand-Myanmar border; kdr mutation