title: Changing Malaria Prevalence on the Kenyan Coast since 1974: Climate, Drugs and Vector Control.
abstract: BACKGROUND
  Progress toward reducing the malaria burden in Africa has been measured, or modeled, using datasets with relatively short time-windows. These restricted temporal analyses may miss the wider context of longer-term cycles of malaria risk and hence may lead to incorrect inferences regarding the impact of intervention.
  
  
  METHODS
  1147 age-corrected Plasmodium falciparum parasite prevalence (PfPR2-10) surveys among rural communities along the Kenyan coast were assembled from 1974 to 2014. A Bayesian conditional autoregressive generalized linear mixed model was used to interpolate to 279 small areas for each of the 41 years since 1974. Best-fit polynomial splined curves of changing PfPR2-10 were compared to a sequence of plausible explanatory variables related to rainfall, drug resistance and insecticide-treated bed net (ITN) use.
  
  
  RESULTS
  P. falciparum parasite prevalence initially rose from 1974 to 1987, dipped in 1991-92 but remained high until 1998. From 1998 onwards prevalence began to decline until 2011, then began to rise through to 2014. This major decline occurred before ITNs were widely distributed and variation in rainfall coincided with some, but not all, short-term transmission cycles. Emerging resistance to chloroquine and introduction of sulfadoxine/pyrimethamine provided plausible explanations for the rise and fall of malaria transmission along the Kenyan coast.
  
  
  CONCLUSIONS
  Progress towards elimination might not be as predictable as we would like, where natural and extrinsic cycles of transmission confound evaluations of the effect of interventions. Deciding where a country lies on an elimination pathway requires careful empiric observation of the long-term epidemiology of malaria transmission.
authors.affiliation: Spatial Health Metrics Group, Kenya Medical Research Institute-Wellcome Trust Research Programme, Nairobi, Kenya; Centre for Tropical Medicine & Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, United Kingdom.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Snow
authors.affiliation: Spatial Health Metrics Group, Kenya Medical Research Institute-Wellcome Trust Research Programme, Nairobi, Kenya.
authors.forename: Eliud
authors.initials: E
authors.lastname: Kibuchi
authors.affiliation: Spatial Health Metrics Group, Kenya Medical Research Institute-Wellcome Trust Research Programme, Nairobi, Kenya.
authors.forename: Stella W
authors.initials: SW
authors.lastname: Karuri
authors.affiliation: Spatial Health Metrics Group, Kenya Medical Research Institute-Wellcome Trust Research Programme, Nairobi, Kenya.
authors.forename: Gilbert
authors.initials: G
authors.lastname: Sang
authors.affiliation: Spatial Health Metrics Group, Kenya Medical Research Institute-Wellcome Trust Research Programme, Nairobi, Kenya.
authors.forename: Caroline W
authors.initials: CW
authors.lastname: Gitonga
authors.affiliation: Eastern and Southern Africa Centre of International Parasite Control, Kenya Medical Research Institute, Nairobi, Kenya.
authors.forename: Charles
authors.initials: C
authors.lastname: Mwandawiro
authors.affiliation: Centre for Tropical Medicine & Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, United Kingdom; Centre for Geographic Medicine-Coast, KEMRI-Wellcome Trust programme, Kilifi, Kenya.
authors.forename: Philip
authors.initials: P
authors.lastname: Bejon
authors.affiliation: Spatial Health Metrics Group, Kenya Medical Research Institute-Wellcome Trust Research Programme, Nairobi, Kenya; Centre for Tropical Medicine & Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, United Kingdom.
authors.forename: Abdisalan M
authors.initials: AM
authors.lastname: Noor
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000962:Antimalarials / Q000627:therapeutic use*; D001499:Bayes Theorem; D002648:Child; D002675:Child, Preschool; D002738:Chloroquine / Q000627:therapeutic use; D002980:Climate; D004338:Drug Combinations; D004351:Drug Resistance; D005260:Female; D006306:Health Surveys; D006801:Humans; D057148:Insecticide-Treated Bednets / Q000706:statistics & numerical data*; D007630:Kenya / Q000453:epidemiology; D016778:Malaria, Falciparum / Q000188:drug therapy / Q000453:epidemiology* / Q000469:parasitology / Q000635:transmission; D008297:Male; D008875:Middle Aged; D009032:Mosquito Control / Q000706:statistics & numerical data*; D010963:Plasmodium falciparum / Q000187:drug effects* / Q000502:physiology; D015995:Prevalence; D011739:Pyrimethamine / Q000627:therapeutic use; D065947:Rainforest; D012189:Retrospective Studies; D013413:Sulfadoxine / Q000627:therapeutic use
chemical_list: D000962:Antimalarials; D004338:Drug Combinations; C001205:fanasil, pyrimethamine drug combination; D013413:Sulfadoxine; D002738:Chloroquine; D011739:Pyrimethamine