title: Molecular analysis of knock down resistance (kdr) mutation and distribution of kdr genotypes in a wild population of Culex quinquefasciatus from India.
abstract: OBJECTIVE
  To investigate the presence of knock down resistance (kdr) mutation, its frequency distribution in the principal vector of bancroftian filariasis, Culex quinquefasciatus from northeastern India, and to relate kdr genotypes with susceptibility and/or resistance to DDT and deltamethrin in this vectors.
  
  
  METHODS
  Adult female mosquitoes were collected by aspiration from human dwellings in two villages, Benganajuli and Rikamari, and two military establishments, Field Units I and II. Insecticide susceptibility tests were performed following WHO methods with 4% DDT and 0.05% deltamethrin. Molecular identification of kdr mutation and genotyping of kdr locus was performed by allele-specific PCR (AS-PCR) and direct sequencing in a subset of samples.
  
  
  RESULTS
  Mosquitoes were resistant to DDT and showed 11.9-41.2% mortality, whereas the knock down bioassay for deltamethrin suggests complete susceptibility to this insecticide in all study sites except Benganajuli. The result of AS-PCR confirmed the presence of three genotypes: susceptible (SS), resistant (RR) and heterozygous (SR) in the population. Genotype frequencies at kdr locus for DDT-resistant individuals conformed with the Hardy-Weinberg proportion, whereas DDT and deltamethrin susceptible individuals differed significantly (P < 0.05). The efficacy of AS-PCR in detecting the correct genotype was not encouraging.
  
  
  CONCLUSIONS
  This is the first report from India on kdr genotyping in C. quinquefasciatus, and it confirms the occurrence of kdr allele in this vector in northeastern India. This finding has serious implications for the filariasis control programmes in India.
authors: Medical Entomology Division, Defence Research Laboratory, Tezpur, India. manas_sarkar54491@yahoo.com
authors: Manas
authors: M
authors: Sarkar
authors: Aparajita
authors: A
authors: Borkotoki
authors: Indra
authors: I
authors: Baruah
authors: Indra Kumar
authors: IK
authors: Bhattacharyya
authors: Ravi Bihari
authors: RB
authors: Srivastava
mesh_terms: D000818:Animals; D003465:Culex / Q000235:genetics*; D003634:DDT / Q000008:administration & dosage; D004351:Drug Resistance / Q000187:drug effects / Q000235:genetics*; D005260:Female; D005368:Filariasis / Q000188:drug therapy / Q000235:genetics*; D055785:Gene Knockdown Techniques / Q000379:methods; D005838:Genotype; D006798:Housing; D007194:India; D007306:Insecticides / Q000008:administration & dosage; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D009570:Nitriles / Q000008:administration & dosage; D011722:Pyrethrins / Q000008:administration & dosage
chemical_list: D007306:Insecticides; D009570:Nitriles; D011722:Pyrethrins; C017180:decamethrin; D003634:DDT