title: Impact of metric and sample size on determining malaria hotspot boundaries.
abstract: The spatial heterogeneity of malaria suggests that interventions may be targeted for maximum impact. It is unclear to what extent different metrics lead to consistent delineation of hotspot boundaries. Using data from a large community-based malaria survey in the western Kenyan highlands, we assessed the agreement between a model-based geostatistical (MBG) approach to detect hotspots using Plasmodium falciparum parasite prevalence and serological evidence for exposure. Malaria transmission was widespread and highly heterogeneous with one third of the total population living in hotspots regardless of metric tested. Moderate agreement (Kappa = 0.424) was observed between hotspots defined based on parasite prevalence by polymerase chain reaction (PCR)- and the prevalence of antibodies to two P. falciparum antigens (MSP-1, AMA-1). While numerous biologically plausible hotspots were identified, their detection strongly relied on the proportion of the population sampled. When only 3% of the population was sampled, no PCR derived hotspots were reliably detected and at least 21% of the population was needed for reliable results. Similar results were observed for hotspots of seroprevalence. Hotspot boundaries are driven by the malaria diagnostic and sample size used to inform the model. These findings warn against the simplistic use of spatial analysis on available data to target malaria interventions in areas where hotspot boundaries are uncertain.
authors.affiliation: Department of Infectious and Tropical Diseases, London School of Hygiene &Tropical Medicine, London, United Kingdom.
authors.forename: Gillian H
authors.initials: GH
authors.lastname: Stresman
authors.affiliation: Faculty of Health and Medicine, Furness College, Lancaster University, Lancaster, United Kingdom.
authors.forename: Emanuele
authors.initials: E
authors.lastname: Giorgi
authors.affiliation: Radboud University Medical Center, Nijmegen, the Netherlands.
authors.forename: Amrish
authors.initials: A
authors.lastname: Baidjoe
authors.affiliation: Department of Ecology and Geography, University of Bath, Bath, United Kingdom.
authors.forename: Phil
authors.initials: P
authors.lastname: Knight
authors.affiliation: Kenya Medical Research Institute, Centre for Global Health Research, Kisumu, Kenya.
authors.forename: Wycliffe
authors.initials: W
authors.lastname: Odongo
authors.affiliation: Kenya Medical Research Institute, Centre for Global Health Research, Kisumu, Kenya.
authors.forename: Chrispin
authors.initials: C
authors.lastname: Owaga
authors.affiliation: Kenya Medical Research Institute, Centre for Global Health Research, Kisumu, Kenya.
authors.forename: Shehu
authors.initials: S
authors.lastname: Shagari
authors.affiliation: Kenya Medical Research Institute, Centre for Global Health Research, Kisumu, Kenya.
authors.forename: Euniah
authors.initials: E
authors.lastname: Makori
authors.affiliation: Department of Infectious and Tropical Diseases, London School of Hygiene &Tropical Medicine, London, United Kingdom.|Kenya Medical Research Institute, Centre for Global Health Research, Kisumu, Kenya.|Malaria Centre, Johns Hopkins Bloomberg School of Public Health, Baltimore, United States.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Stevenson
authors.affiliation: Department of Infectious and Tropical Diseases, London School of Hygiene &Tropical Medicine, London, United Kingdom.
authors.forename: Chris
authors.initials: C
authors.lastname: Drakeley
authors.affiliation: Department of Infectious and Tropical Diseases, London School of Hygiene &Tropical Medicine, London, United Kingdom.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Cox
authors.affiliation: Department of Infectious and Tropical Diseases, London School of Hygiene &Tropical Medicine, London, United Kingdom.|Radboud University Medical Center, Nijmegen, the Netherlands.
authors.forename: Teun
authors.initials: T
authors.lastname: Bousema
authors.affiliation: Faculty of Health and Medicine, Furness College, Lancaster University, Lancaster, United Kingdom.|Institute of Infection and Global Health, University of Liverpool, Liverpool, United Kingdom.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Diggle
mesh_terms: D000293:Adolescent; D000913:Antibodies, Protozoan / Q000235:genetics*; D002648:Child; D005260:Female; D006801:Humans; D007630:Kenya; D016778:Malaria, Falciparum / Q000453:epidemiology* / Q000235:genetics / Q000469:parasitology; D008297:Male; D020066:Merozoite Surface Protein 1 / Q000235:genetics*; D010963:Plasmodium falciparum / Q000235:genetics* / Q000472:pathogenicity; D018401:Sample Size; D016036:Seroepidemiologic Studies; D062206:Spatial Analysis
chemical_list: D000913:Antibodies, Protozoan; D020066:Merozoite Surface Protein 1