title: Susceptibility status of Culex quinquefasciatus (Diptera: Culicidae) populations to the chemical insecticide temephos in Pernambuco, Brazil.
abstract: BACKGROUND
  Culex quinquefasciatus is the vector of many agents of human diseases, including Wuchereria bancrofti, the parasite that causes bancroftian filariasis, an endemic disease in Pernambuco State, Brazil. Although temephos is not currently used to control C. quinquefasciatus, the species might be under a selection process from incidental exposure to this compound. This study aimed to evaluate the susceptibility status of C. quinquefasciatus to temephos, using bioassays, and to investigate its putative resistance mechanisms through biochemical assays and screening of the G119S mutation in the acetylcholinesterase gene, which is associated with organophosphate resistance, carried out by PCR and sequencing.
  
  
  RESULTS
  The results showed that only mosquitoes from Santa Cruz do Capibaribe (SC) had an alteration in their susceptibility status (RR = 7.2-fold), while the other populations were all susceptible to the insecticide. Biochemical assays showed increased activity for all esterases in SC, as well as evidence of acetylcholinesterase insensitivity. The G119S mutation was detected in this population with a frequency of 0.11, but it was not found in the remaining populations.
  
  
  CONCLUSIONS
  These data show that mechanisms of temephos resistance have been selected in natural C. quinquefasciatus populations from Pernambuco, which could undermine future control actions.
authors.affiliation: Department of Entomology, Centro de Pesquisas Aggeu Magalhães/FIOCRUZ, Recife-PE, Brazil; Postgraduate Programme of Animal Biology/UFPE.
authors.forename: Liliane Barbosa
authors.initials: LB
authors.lastname: Amorim
authors.forename: Elisama
authors.initials: E
authors.lastname: Helvecio
authors.forename: Cláudia Maria Fontes
authors.initials: CM
authors.lastname: de Oliveira
authors.forename: Constância Flávia Junqueira
authors.initials: CF
authors.lastname: Ayres
mesh_terms: D000110:Acetylcholinesterase / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001681:Biological Assay; D001938:Brazil; D003465:Culex / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism; D007306:Insecticides / Q000633:toxicity*; D009032:Mosquito Control; D009154:Mutation; D000002:Temefos / Q000633:toxicity*
chemical_list: D019476:Insect Proteins; D007306:Insecticides; D000110:Acetylcholinesterase; D000002:Temefos
keywords: Culex quinquefasciatus; acetylcholinesterase; bioassay; detoxifying enzymes; temephos resistance