title: Inheritance and heritability of deltamethrin resistance under laboratory conditions of Triatoma infestans from Bolivia.
abstract: BACKGROUND
  Over the last few decades, pyrethroid-resistant in Triatoma infestans populations have been reported, mainly on the border between Argentina and Bolivia. Understanding the genetic basis of inheritance mode and heritability of resistance to insecticides under laboratory conditions is crucial for vector management and monitoring of insecticide resistance. Currently, few studies have been performed to characterize the inheritance mode of resistance to pyrethroids in T. infestans; for this reason, the present study aims to characterize the inheritance and heritability of deltamethrin resistance in T. infestans populations from Bolivia with different toxicological profiles.
  
  
  METHODS
  Experimental crosses were performed between a susceptible (S) colony and resistant (R) and reduced susceptibility (RS) colonies in both directions (♀ x ♂ and ♂ x ♀), and inheritance mode was determined based on degree of dominance (DO) and effective dominance (D(ML)). In addition, realized heritability (h(2)) was estimated based on a resistant colony, and select pressure was performed for two generations based on the diagnostic dose (10 ng. i. a. /nymph). The F1 progeny of the experimental crosses and the selection were tested by a standard insecticide resistance bioassay.
  
  
  RESULTS
  The result for DO and D(ML) (< 1) indicates that resistance is an incompletely dominant character, and inheritance is autosomal, not sex-linked. The LD50 for F1 of ♀S x ♂R and ♂S x ♀R was 0.74 and 3.97, respectively, which is indicative of dilution effect. In the resistant colony, after selection pressure, the value of h(2) was 0.37; thus, the LD50 value increased 2.25-fold (F2) and 26.83-fold (F3) compared with the parental colony.
  
  
  CONCLUSIONS
  The inheritance mode of resistance of T. infestans to deltamethrin, is autosomal and an incompletely dominant character; this is a previously known process, confirmed in the present study on T. infestans populations from Bolivia. The lethal doses (LD50) increase from one generation to another rapidly after selection pressure with deltamethrin. This suggests that resistance is an additive and cumulative factor, mainly in highly structured populations with limited dispersal capacity, such as T. infestans. This phenomenon was demonstrated for the first time for T. infestans in the present study. These results are very important for vector control strategies in problematic areas where high resistance ratios of T. infestans have been reported.
authors.affiliation: Laboratório de Referência em Triatomíneos e Epidemiologia da Doença de Chagas, Centro de Pesquisas René Rachou - FIOCRUZ Minas, Belo Horizonte, Brazil. marinelybustamante@gmail.com.
authors.forename: Marinely Bustamante
authors.initials: MB
authors.lastname: Gomez
authors.affiliation: Laboratório de Referência em Triatomíneos e Epidemiologia da Doença de Chagas, Centro de Pesquisas René Rachou - FIOCRUZ Minas, Belo Horizonte, Brazil. grasielle@cpqrr.fiocruz.br.
authors.forename: Grasielle D'Avila Caldas
authors.initials: GD
authors.lastname: Pessoa
authors.affiliation: Laboratório de Referência em Triatomíneos e Epidemiologia da Doença de Chagas, Centro de Pesquisas René Rachou - FIOCRUZ Minas, Belo Horizonte, Brazil. aline.rosa@cpqrr.fiocruz.br.
authors.forename: Aline Cristine Luiz
authors.initials: AC
authors.lastname: Rosa
authors.affiliation: Laboratório de Referência em Triatomíneos e Epidemiologia da Doença de Chagas, Centro de Pesquisas René Rachou - FIOCRUZ Minas, Belo Horizonte, Brazil. jorgeespinozaecheverria@gmail.com.
authors.forename: Jorge Espinoza
authors.initials: JE
authors.lastname: Echeverria
authors.affiliation: Laboratório de Referência em Triatomíneos e Epidemiologia da Doença de Chagas, Centro de Pesquisas René Rachou - FIOCRUZ Minas, Belo Horizonte, Brazil. diotaiut@cpqrr.fiocruz.br.
authors.forename: Liléia Gonçalves
authors.initials: LG
authors.lastname: Diotaiuti
mesh_terms: D000818:Animals; D001838:Bolivia; D003433:Crosses, Genetic; D005799:Genes, Dominant; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology*; D007928:Lethal Dose 50; D009570:Nitriles / Q000494:pharmacology*; D011722:Pyrethrins / Q000494:pharmacology*; D012641:Selection, Genetic; D014224:Triatoma / Q000187:drug effects* / Q000235:genetics; D014918:Wills
chemical_list: D007306:Insecticides; D009570:Nitriles; D011722:Pyrethrins; C017180:decamethrin