title: Modelling the relative abundance of the primary African vectors of malaria before and after the implementation of indoor, insecticide-based vector control.
abstract: BACKGROUND
  Malaria remains a heavy burden across sub-Saharan Africa where transmission is maintained by some of the world's most efficient vectors. Indoor insecticide-based control measures have significantly reduced transmission, yet elimination remains a distant target. Knowing the relative abundance of the primary vector species can provide transmission models with much needed information to guide targeted control measures. Moreover, understanding how existing interventions are impacting on these relative abundances highlights where alternative control (e.g., larval source management) is needed.
  
  
  METHODS
  Using the habitat suitability probabilities generated by predictive species distribution models combined with data collated from the literature, a multinomial generalized additive model was applied to produce relative abundance estimates for Anopheles arabiensis, Anopheles funestus and Anopheles gambiae/Anopheles coluzzii. Using pre- and post-intervention abundance data, estimates of the effect of indoor insecticide-based interventions on these relative abundances were made and are illustrated in post-intervention maps.
  
  
  RESULTS
  Conditional effect plots and relative abundance maps illustrate the individual species' predicted habitat suitability and how they interact when in sympatry. Anopheles arabiensis and An. funestus show an affinity in habitat preference at the expense of An. gambiae/An. coluzzii, whereas increasing habitat suitability for An. gambiae/An. coluzzii is conversely less suitable for An. arabiensis but has little effect on An. funestus. Indoor insecticide-based interventions had a negative impact on the relative abundance of An. funestus, and a lesser effect on An. arabiensis. Indoor residual spraying had the greatest impact on the relative abundance of An. funestus, and a lesser effect on An. gambiae/An. coluzzii. Insecticide-treated bed nets reduced the relative abundance of both species equally. These results do not indicate changes in the absolute abundance of these species, which may be reduced for all species overall.
  
  
  CONCLUSIONS
  The maps presented here highlight the interactions between the primary vector species in sub-Saharan Africa and demonstrate that An. funestus is more susceptible to certain indoor-based insecticide interventions than An. gambiae/An. coluzzii, which in turn, is more susceptible than An. arabiensis. This may provide An. arabiensis with a competitive advantage where it is found in sympatry with other more endophilic vectors, and potentially increase the need for outdoor-based vector interventions to deal with any residual transmission barring the way to malaria elimination.
authors.affiliation: Spatial Ecology and Epidemiology Group, Department of Zoology, University of Oxford, Oxford, OX1 3PS, UK. marianne.sinka@zoo.ox.ac.uk.
authors.forename: Marianne E
authors.initials: ME
authors.lastname: Sinka
authors.affiliation: Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK. nick.golding.research@gmail.com.
authors.forename: Nick
authors.initials: N
authors.lastname: Golding
authors.affiliation: Spatial Ecology and Epidemiology Group, Department of Zoology, University of Oxford, Oxford, OX1 3PS, UK. claire.massey@zoo.ox.ac.uk.
authors.forename: N Claire
authors.initials: NC
authors.lastname: Massey
authors.affiliation: Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK. awiebe@well.ox.ac.uk.
authors.forename: Antoinette
authors.initials: A
authors.lastname: Wiebe
authors.affiliation: Spatial Ecology and Epidemiology Group, Department of Zoology, University of Oxford, Oxford, OX1 3PS, UK. zhi.huang@zoo.ox.ac.uk.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Huang
authors.affiliation: Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK. simon.hay@well.ox.ac.uk.|Institute for Health Metrics and Evaluation, University of Washington, Seattle, WA, 98121, USA. simon.hay@well.ox.ac.uk.|Fogarty International Center, National Institutes of Health, Bethesda, MD, 20892-2220, USA. simon.hay@well.ox.ac.uk.
authors.forename: Simon I
authors.initials: SI
authors.lastname: Hay
authors.affiliation: Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK. clmoyes@well.ox.ac.uk.
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Moyes
mesh_terms: D000349:Africa; D000818:Animals; D000852:Anopheles / Q000187:drug effects*; D006801:Humans; D007303:Insect Vectors / Q000187:drug effects*; D057148:Insecticide-Treated Bednets; D007306:Insecticides / Q000494:pharmacology* / Q000627:therapeutic use; D008288:Malaria / Q000517:prevention & control* / Q000635:transmission*; D008954:Models, Biological; D009032:Mosquito Control / Q000706:statistics & numerical data*
chemical_list: D007306:Insecticides