title: Insecticide resistance of Triatoma infestans (Hemiptera, Reduviidae) vector of Chagas disease in Bolivia.
abstract: OBJECTIVE
  To define the insecticide resistance status of Triatoma infestans to deltamethrin (pyrethroid), malathion (organophosphate) and bendiocarb (carbamate) in Bolivia.
  
  
  METHODS
  Fifty populations of T. infestans were sampled in Bolivian human dwellings. Quantal response data were obtained by topical applications of 0.2 μl of insecticide-acetone solutions on nymphs N1 of the F1 generations. For most populations, dose-mortality relationships and resistance ratios (RR) were analysed. Discriminating concentrations were established for each insecticide with a susceptible reference strain and used on the other field populations. A tarsal-contact diagnostic test using insecticide impregnated papers was designed to rapidly identify deltamethrin-resistant populations in the field.
  
  
  RESULTS
  Discriminating concentrations for topical applications were 5, 70 and 120 ng active ingredient per insect for deltamethrin, bendiocarb and malathion, respectively. The diagnostic concentration for deltamethrin was 0.30% for the 1-h exposure by tarsal contact. All populations sampled in human dwellings exhibited significant levels of resistance to deltamethrin, from 6 to 491 and varied among regions. Resistant populations did not recover complete susceptibility to deltamethrin when the synergist piperonyl butoxide (PBO) was used. None of the sampled populations exhibited significant resistance to bendiocarb (all RR(50) < 1.8) or malathion (all RR(50) < 2.2).
  
  
  CONCLUSIONS
  In Bolivia, most 'domestic' T. infestans populations are resistant to deltamethrin. Because insecticide vector control is the only selection pressure, resistance likely originates from it. Switching from pyrethroids to organophosphates or carbamates could be a short-term solution to control this vector, but other alternative integrated control strategies should also be considered in the long term.
authors.affiliation: Institut de Recherche pour le Développement, Montpellier, France. Frederic.Lardeux@ird.fr
authors.forename: Frédéric
authors.initials: F
authors.lastname: Lardeux
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Depickère
authors.forename: Stéphane
authors.initials: S
authors.lastname: Duchon
authors.forename: Tamara
authors.initials: T
authors.lastname: Chavez
mesh_terms: D000818:Animals; D001838:Bolivia; D014355:Chagas Disease / Q000635:transmission*; D004305:Dose-Response Relationship, Drug; D006430:Hemiptera; D006801:Humans; D007303:Insect Vectors / Q000187:drug effects*; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology*; D008294:Malathion / Q000494:pharmacology*; D009570:Nitriles / Q000494:pharmacology*; D048448:Phenylcarbamates / Q000494:pharmacology*; D011722:Pyrethrins / Q000494:pharmacology*; D020064:Reduviidae; D014224:Triatoma / Q000187:drug effects*
chemical_list: D007306:Insecticides; D009570:Nitriles; D048448:Phenylcarbamates; D011722:Pyrethrins; C017180:decamethrin; C007725:bendiocarb; D008294:Malathion