title: Long-term trends in Anopheles gambiae insecticide resistance in Côte d'Ivoire.
abstract: BACKGROUND
  Malaria control is heavily dependent on the use of insecticides that target adult mosquito vectors via insecticide treated nets (ITNs) or indoor residual spraying (IRS). Four classes of insecticide are approved for IRS but only pyrethroids are available for ITNs. The rapid rise in insecticide resistance in African malaria vectors has raised alarms about the sustainability of existing malaria control activities. This problem might be particularly acute in Côte d'Ivoire where resistance to all four insecticide classes has recently been recorded. Here we investigate temporal trends in insecticide resistance across the ecological zones of Côte d'Ivoire to determine whether apparent pan-African patterns of increasing resistance are detectable and consistent across insecticides and areas.
  
  
  METHODS
  We combined data on insecticide resistance from a literature review, and bioassays conducted on field-caught Anopheles gambiae mosquitoes for the four WHO-approved insecticide classes for ITN/IRS. The data were then mapped using Geographical Information Systems (GIS) and the IR mapper tool to provide spatial and temporal distribution data on insecticide resistance in An. gambiae sensu lato from Côte d'Ivoire between 1993 and 2014.
  
  
  RESULTS
  Bioassay mortality decreased over time for all insecticide classes, though with significant spatiotemporal variation, such that stronger declines were observed in the southern ecological zone for DDT and pyrethroids than in the central zone, but with an apparently opposite effect for the carbamate and organophosphate. Variation in relative abundance of the molecular forms, coupled with dramatic increase in kdr 1014F frequency in M forms (An. coluzzii) seems likely to be a contributory factor to these patterns. Although records of resistance across insecticide classes have become more common, the number of classes tested in studies has also increased, precluding a conclusion that multiple resistance has also increased.
  
  
  CONCLUSIONS
  Our analyses attempted synthesis of 22 years of bioassay data from Côte d'Ivoire, and despite a number of caveats and potentially confounding variables, suggest significant but spatially-variable temporal trends in insecticide resistance. In the light of such spatio-temporal dynamics, regular, systematic and spatially-expanded monitoring is warranted to provide accurate information on insecticide resistance for control programme management.
authors.affiliation: Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK. C.Edi@liverpool.ac.uk.|Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, 01 BP 1303, Abidjan 01, Côte d'Ivoire. C.Edi@liverpool.ac.uk.
authors.forename: Constant A V
authors.initials: CA
authors.lastname: Edi
authors.affiliation: Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK. benjamin.koudou@lstmed.ac.uk.|Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, 01 BP 1303, Abidjan 01, Côte d'Ivoire. benjamin.koudou@lstmed.ac.uk.|Université Nangui-Abrogoua, UFR Sciences de la Nature, 02 BP 801, Abidjan 02, Côte d'Ivoire. benjamin.koudou@lstmed.ac.uk.
authors.forename: Benjamin G
authors.initials: BG
authors.lastname: Koudou
authors.affiliation: Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, 01 BP 1303, Abidjan 01, Côte d'Ivoire. louisebellai@yahoo.fr.|Université Felix Houphouët-Boigny de Cocody, Abidjan, 22 BP 582, Côte d'Ivoire. louisebellai@yahoo.fr.
authors.forename: Louise
authors.initials: L
authors.lastname: Bellai
authors.affiliation: Université Felix Houphouët-Boigny de Cocody, Abidjan, 22 BP 582, Côte d'Ivoire. adjamaurice@yahoo.fr.|Institut Pierre Richet (IPR), Abidjan, BP 47, Côte d'Ivoire. adjamaurice@yahoo.fr.
authors.forename: Akre M
authors.initials: AM
authors.lastname: Adja
authors.affiliation: Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, 01 BP 1303, Abidjan 01, Côte d'Ivoire. ms.chouaibou@gmail.com.
authors.forename: Mouhamadou
authors.initials: M
authors.lastname: Chouaibou
authors.affiliation: Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, 01 BP 1303, Abidjan 01, Côte d'Ivoire. bassirou.bonfoh@csrs.ci.
authors.forename: Bassirou
authors.initials: B
authors.lastname: Bonfoh
authors.affiliation: Robertson Centre for Biostatistics, University of Glasgow, Boyd Orr Building, Glasgow, G12 8QQ, UK. sarah.barry@glasgow.ac.uk.
authors.forename: Sarah J E
authors.initials: SJ
authors.lastname: Barry
authors.affiliation: Boyd Orr Centre for Population and Ecosystem Health, Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Graham Kerr Building, Glasgow, G12 8QQ, UK. paul.johnson@glasgow.ac.uk.
authors.forename: Paul C D
authors.initials: PC
authors.lastname: Johnson
authors.affiliation: Epidemiology and Public Health Department, Swiss Tropical and Public Health Institute, Socinstrasse 57, PO Box, CH-4002, Basel, Switzerland. Pie.Mueller@unibas.ch.|University of Basel, Petersplatz 1, CH-4003, Basel, Switzerland. Pie.Mueller@unibas.ch.
authors.forename: Pie
authors.initials: P
authors.lastname: Müller
authors.affiliation: Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK. stefan.dongus@unibas.ch.|Epidemiology and Public Health Department, Swiss Tropical and Public Health Institute, Socinstrasse 57, PO Box, CH-4002, Basel, Switzerland. stefan.dongus@unibas.ch.|University of Basel, Petersplatz 1, CH-4003, Basel, Switzerland. stefan.dongus@unibas.ch.
authors.forename: Stefan
authors.initials: S
authors.lastname: Dongus
authors.affiliation: Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, 01 BP 1303, Abidjan 01, Côte d'Ivoire. eliezerngoran@yahoo.fr.|Université Felix Houphouët-Boigny de Cocody, Abidjan, 22 BP 582, Côte d'Ivoire. eliezerngoran@yahoo.fr.
authors.forename: Eliezer K
authors.initials: EK
authors.lastname: N'Goran
authors.affiliation: Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK. Hilary.Ranson@lstmed.ac.uk.
authors.forename: Hilary
authors.initials: H
authors.lastname: Ranson
authors.affiliation: Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK. David.Weetman@lstmed.ac.uk.
authors.forename: David
authors.initials: D
authors.lastname: Weetman
mesh_terms: D000818:Animals; D000852:Anopheles / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D007560:Cote d'Ivoire; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism; D007305:Insecticide Resistance; D007306:Insecticides
chemical_list: D019476:Insect Proteins; D007306:Insecticides