title: A significant increase in kdr in Anopheles gambiae is associated with an intensive vector control intervention in Burundi highlands.
abstract: OBJECTIVE
  In Burundi, the occurrence of the knock down resistance (kdr) mutation in Anopheles gambiae sensu lato (s.l.) was determined for six consecutive years within the framework of a vector control programme. Findings were also linked with the insecticide resistance status observed with bioassay in An. gambiae s.l. and An. funestus.
  
  
  RESULTS
  The proportion of An. gambiae s.l. carrying the East Leu-Ser kdr mutation was 1% before the spraying intervention in 2002; by 2007 it was 86% in sprayed valleys and 67% in untreated valleys. Multivariate analysis showed that increased risk of carrying the kdr mutation is associated with spraying interventions, location and time. In bioassays conducted between 2005 and 2007 at five sites, An. funestus was susceptible to permethrin, deltamethrin and DDT. Anopheles gambiae s.l. remained susceptible or tolerant to deltamethrin and resistant to DDT and permethrin, but only when kdr allele carriers reached 90% of the population.
  
  
  CONCLUSIONS
  The cross-resistance against DDT and permethrin in Karuzi suggests a possible kdr resistance mechanism. Nevertheless, the homozygous resistant genotype alone does not entirely explain the bioassay results, and other mechanisms conferring resistance cannot be ruled out. After exposure to all three insecticides, homozygote individuals for the kdr allele dominate among the surviving An. gambiae s.l. This confirms the potential selection pressure of pyrethroids on kdr mutation. However, the high occurrence of the kdr mutation, even at sites far from the sprayed areas, suggests a selection pressure other than that exerted by the vector control programme.
authors.affiliation: Department of Parasitology, Prince Leopold Institute of Tropical Medicine, Antwerp, Belgium. nprotopopoff@itg.be
authors.forename: Natacha
authors.initials: N
authors.lastname: Protopopoff
authors.forename: Katrijn
authors.initials: K
authors.lastname: Verhaeghen
authors.forename: Wim
authors.initials: W
authors.lastname: Van Bortel
authors.forename: Patricia
authors.initials: P
authors.lastname: Roelants
authors.forename: Tanguy
authors.initials: T
authors.lastname: Marcotty
authors.forename: Dismas
authors.initials: D
authors.lastname: Baza
authors.forename: Umberto
authors.initials: U
authors.lastname: D'Alessandro
authors.forename: Marc
authors.initials: M
authors.lastname: Coosemans
mesh_terms: D000818:Animals; D000852:Anopheles / Q000187:drug effects / Q000235:genetics*; D002063:Burundi; D003634:DDT / Q000494:pharmacology; D017344:Genes, Insect; D005838:Genotype; D006720:Homozygote; D007305:Insecticide Resistance / Q000235:genetics*; D007306:Insecticides / Q000494:pharmacology; D009032:Mosquito Control; D009154:Mutation; D009570:Nitriles / Q000494:pharmacology; D026023:Permethrin / Q000494:pharmacology; D011722:Pyrethrins / Q000494:pharmacology
chemical_list: D007306:Insecticides; D009570:Nitriles; D011722:Pyrethrins; C017180:decamethrin; D026023:Permethrin; D003634:DDT