title: Impact of agriculture on the selection of insecticide resistance in the malaria vector Anopheles gambiae: a multigenerational study in controlled conditions.
abstract: BACKGROUND
  Resistance of mosquitoes to insecticides is mainly attributed to their adaptation to vector control interventions. Although pesticides used in agriculture have been frequently mentioned as an additional force driving the selection of resistance, only a few studies were dedicated to validate this hypothesis and characterise the underlying mechanisms. While insecticide resistance is rising dramatically in Africa, deciphering how agriculture affects resistance is crucial for improving resistance management strategies. In this context, the multigenerational effect of agricultural pollutants on the selection of insecticide resistance was examined in Anopheles gambiae.
  
  
  METHODS
  An urban Tanzanian An. gambiae population displaying a low resistance level was used as a parental strain for a selection experiment across 20 generations. At each generation larvae were selected with a mixture containing pesticides and herbicides classically used in agriculture in Africa. The resistance levels of adults to deltamethrin, DDT and bendiocarb were compared between the selected and non-selected strains across the selection process together with the frequency of kdr mutations. A microarray approach was used for pinpointing transcription level variations selected by the agricultural pesticide mixture at the adult stage.
  
  
  RESULTS
  A gradual increase of adult resistance to all insecticides was observed across the selection process. The frequency of the L1014S kdr mutation rose from 1.6% to 12.5% after 20 generations of selection. Microarray analysis identified 90 transcripts over-transcribed in the selected strain as compared to the parental and the non-selected strains. Genes encoding cuticle proteins, detoxification enzymes, proteins linked to neurotransmitter activity and transcription regulators were mainly affected. RT-qPCR transcription profiling of candidate genes across multiple generations supported their link with insecticide resistance.
  
  
  CONCLUSIONS
  This study confirms the potency of agriculture in selecting for insecticide resistance in malaria vectors. We demonstrated that the recurrent exposure of larvae to agricultural pollutants can select for resistance mechanisms to vector control insecticides at the adult stage. Our data suggest that in addition to selected target-site resistance mutations, agricultural pollutants may also favor cuticle, metabolic and synaptic transmission-based resistance mechanisms. These results emphasize the need for integrated resistance management strategies taking into account agriculture activities.
authors.affiliation: Laboratoire d'Ecologie Alpine, UMR CNRS 5553, BP 53, 38041, Grenoble cedex 09, France. theresia.nkya@gmail.com.|Université Grenoble-Alpes, Grenoble, France. theresia.nkya@gmail.com.|National Institute of Medical Research of Tanzania. Amani Medical Research Centre, P. O. Box 81, Muheza, Tanga, Tanzania. theresia.nkya@gmail.com.
authors.forename: Theresia Estomih
authors.initials: TE
authors.lastname: Nkya
authors.affiliation: Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke place, L35QA, Liverpool, UK. rodolphe.poupardin@gmail.com.
authors.forename: Rodolphe
authors.initials: R
authors.lastname: Poupardin
authors.affiliation: Laboratoire d'Ecologie Alpine, UMR CNRS 5553, BP 53, 38041, Grenoble cedex 09, France. frederic.laporte@ujf-grenoble.fr.|Université Grenoble-Alpes, Grenoble, France. frederic.laporte@ujf-grenoble.fr.
authors.forename: Frederic
authors.initials: F
authors.lastname: Laporte
authors.affiliation: Laboratoire d'Ecologie Alpine, UMR CNRS 5553, BP 53, 38041, Grenoble cedex 09, France. ig.akhouayri@yahoo.com.|Université Grenoble-Alpes, Grenoble, France. ig.akhouayri@yahoo.com.
authors.forename: Idir
authors.initials: I
authors.lastname: Akhouayri
authors.affiliation: KCM College of Tumaini University, P. O. Box. 2240, Moshi, Tanzania. fwmosha@kcmcollege.ac.tz.
authors.forename: Franklin
authors.initials: F
authors.lastname: Mosha
authors.affiliation: National Institute of Medical Research of Tanzania. Amani Medical Research Centre, P. O. Box 81, Muheza, Tanga, Tanzania. smagesa@hotmail.com.|RTI International-Tanzania, P.O.Box 369, Dar es Salaam, Tanzania. smagesa@hotmail.com.
authors.forename: Stephen
authors.initials: S
authors.lastname: Magesa
authors.affiliation: National Institute of Medical Research of Tanzania. Amani Medical Research Centre, P. O. Box 81, Muheza, Tanga, Tanzania. wkisinza@nimr.or.tz.
authors.forename: William
authors.initials: W
authors.lastname: Kisinza
authors.affiliation: Laboratoire d'Ecologie Alpine, UMR CNRS 5553, BP 53, 38041, Grenoble cedex 09, France. jean-philippe.david@ujf-grenoble.fr.|Université Grenoble-Alpes, Grenoble, France. jean-philippe.david@ujf-grenoble.fr.
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: David
mesh_terms: D000383:Agriculture; D000818:Animals; D000852:Anopheles / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation; D005838:Genotype; D007303:Insect Vectors / Q000187:drug effects* / Q000469:parasitology; D007305:Insecticide Resistance / Q000235:genetics*; D007306:Insecticides / Q000008:administration & dosage / Q000494:pharmacology*; D008288:Malaria / Q000635:transmission*; D040081:Protein Array Analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012641:Selection, Genetic; D059467:Transcriptome
chemical_list: D007306:Insecticides