title: Pyrethroid-resistance and presence of two knockdown resistance (kdr) mutations, F1534C and a novel mutation T1520I, in Indian Aedes aegypti.
abstract: BACKGROUND
  Control of Aedes aegypti, the mosquito vector of dengue, chikungunya and yellow fever, is a challenging task. Pyrethroid insecticides have emerged as a preferred choice for vector control but are threatened by the emergence of resistance. The present study reports a focus of pyrethroid resistance and presence of two kdr mutations--F1534C and a novel mutation T1520I, in Ae. aegypti from Delhi, India.
  
  
  RESULTS
  Insecticide susceptibility status of adult-female Ae. aegypti against DDT (4%), deltamethrin (0.05%) and permethrin (0.75%) was determined using WHO's standard insecticide susceptibility kit, which revealed resistance to DDT, deltamethrin and permethrin with corrected mortalities of 35%, 72% and 76% respectively. Mosquitoes were screened for the presence of kdr mutations including those reported earlier (I1011V/M, V1016G/I, F1534C, D1794Y and S989P), which revealed the presence of F1534C and a novel mutation T1520I. Highly specific PCR-RFLP assays were developed for genotyping of these two mutations. Genotyping using allele specific PCR and new PCR-RFLP assays revealed a high frequency of F1534C (0.41-0.79) and low frequency of novel mutation T1520I (0.13). The latter was observed to be tightly linked with F1534C and possibly serve as a compensatory mutation. A positive association of F1534C mutation with DDT and deltamethrin resistance in Ae. aegypti was established. However, F1534C-kdr did not show significant protection against permethrin.
  
  
  CONCLUSIONS
  The Aedes aegypti population of Delhi is resistant to DDT, deltamethrin and permethrin. Two kdr mutations, F1534C and a novel mutation T1520I, were identified in this population. This is the first report of kdr mutations being present in the Indian Ae. aegypti population. Highly specific PCR-RFLP assays were developed for discrimination of alleles at both kdr loci. A positive association of F1534C mutation with DDT and deltamethrin resistance was confirmed.
authors.affiliation: National Institute of Malaria Research, Sector 8, Dwarka, Delhi, India.
authors.forename: Raja Babu S
authors.initials: RB
authors.lastname: Kushwah
authors.affiliation: National Institute of Malaria Research, Sector 8, Dwarka, Delhi, India.
authors.forename: Cherry L
authors.initials: CL
authors.lastname: Dykes
authors.affiliation: School of Life Sciences, Indira Gandhi National Open University, Maidangarhi, New Delhi, India.
authors.forename: Neera
authors.initials: N
authors.lastname: Kapoor
authors.affiliation: National Institute of Malaria Research, Sector 8, Dwarka, Delhi, India.
authors.forename: Tridibes
authors.initials: T
authors.lastname: Adak
authors.affiliation: National Institute of Malaria Research, Sector 8, Dwarka, Delhi, India.
authors.forename: Om P
authors.initials: OP
authors.lastname: Singh
mesh_terms: D000330:Aedes / Q000187:drug effects* / Q000235:genetics; D000483:Alleles; D000818:Animals; D005260:Female; D005838:Genotype; D007194:India; D007305:Insecticide Resistance / Q000235:genetics*; D007306:Insecticides / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009154:Mutation; D011722:Pyrethrins / Q000494:pharmacology*
chemical_list: D007306:Insecticides; D011722:Pyrethrins