title: Susceptibility of Triatoma sordida Stal, 1859 (Hemiptera: Reduviidae) to alpha-cypermethrin under natural climatic conditions.
abstract: BACKGROUND
  Despite the recommendations by interpretation of resistance ratios obtained in laboratory bioassays, little is known about the actual impact of these results in the effectiveness of vector control activities in the field. In this context, our objective was to determine the mean value of different resistance ratios obtained by laboratory bioassays performed as part of the chemical control strategies of Triatoma sordida in the field.
  
  
  METHODS
  Field bioassays were developed in Monte Azul and Coração de Jesus (Southeast, Brazil). In each location, samples were formed with three domestic units treated with alpha-cypermethrin 20.0% (Alfatek (r) 200 SC). One day after spraying, 10 fifth-instar nymphs remained in contact with the surfaces treated (adobe with plaster, adobe without plaster, or wood) with insecticide in plastic cones for 72h. Three cones were exposed inside the intradomicile and the peridomicile. The insects in the control group were exposed to an insecticide-free piece of cardboard. Mortality was measured 72h after removal of the insects from the treated surfaces. The tests were realized in triplicate.
  
  
  RESULTS
  Mortality was 100.0% in all locations, except for Monte Azul; Landinho (96.6%) and Coração de Jesus; Barriguda (96.6%).
  
  
  CONCLUSIONS
  Although the resistant populations in laboratory tests proved to be susceptible in the field, this observation is not sufficient to suggest that the cut-off points used to justify the resistance ratio should be changed. In this sense, we recommend that laboratory and field bioassays are carried out with a greater number of Triatominae populations to allow more in-depth consideration of the subject.
authors: Laboratório de Referência em Triatomíneos e Epidemiologia da Doença de Chagas, Centro de Pesquisas René Rachou, Fundação Oswaldo Cruz, Belo Horizonte, Minas Gerais, BR.
authors: Grasielle Caldas Dávila
authors: GC
authors: Pessoa
authors: Laboratório de Referência em Triatomíneos e Epidemiologia da Doença de Chagas, Centro de Pesquisas René Rachou, Fundação Oswaldo Cruz, Belo Horizonte, Minas Gerais, BR.
authors: Aline Cristine Luiz
authors: AC
authors: Rosa
authors: Laboratório de Referência em Triatomíneos e Epidemiologia da Doença de Chagas, Centro de Pesquisas René Rachou, Fundação Oswaldo Cruz, Belo Horizonte, Minas Gerais, BR.
authors: Letícia
authors: L
authors: Cavalari
authors: Gerência Regional de Saúde de Montes Claros, Montes Claros, Minas Gerais, BR.
authors: João Geraldo de
authors: JG
authors: Rezende
authors: Secretaria de Saúde do Estado de Minas Gerais, Governo do Estado de Minas Gerais, Belo Horizonte, Minas Gerais, BR.
authors: Bernardino Vaz
authors: BV
authors: de Mello
authors: Laboratório de Referência em Triatomíneos e Epidemiologia da Doença de Chagas, Centro de Pesquisas René Rachou, Fundação Oswaldo Cruz, Belo Horizonte, Minas Gerais, BR.
authors: Liléia
authors: L
authors: Diotaiuti
mesh_terms: D000818:Animals; D001681:Biological Assay; D014355:Chagas Disease / Q000635:transmission; D017753:Ecosystem; D007303:Insect Vectors; D007305:Insecticide Resistance; D007928:Lethal Dose 50; D011722:Pyrethrins; D014224:Triatoma
chemical_list: D011722:Pyrethrins; C017160:cypermethrin