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Reference: Philip Bejon, Thomas N. Williams, Anne Liljander et al., (2010). Stable and unstable malaria hotspots in longitudinal cohort studies in Kenya. PLoS Medicine, 7 (7), Article: e1000304.Citable link to this page:


Stable and unstable malaria hotspots in longitudinal cohort studies in Kenya

Abstract: Background: Infectious diseases often demonstrate heterogeneity of transmission among host populations. This heterogeneity reduces the efficacy of control strategies, but also implies that focusing control strategies on hotspots of transmission could be highly effective.Methods and findings: In order to identify hotspots of malaria transmission, we analysed longitudinal data on febrile malaria episodes, asymptomatic parasitaemia, and antibody titres over 12 y from 256 homesteads in three study areas in Kilifi District on the Kenyan coast. We examined heterogeneity by homestead, and identified groups of homesteads that formed hotspots using a spatial scan statistic. Two types of statistically significant hotspots were detected; stable hotspots of asymptomatic parasitaemia and unstable hotspots of febrile malaria. The stable hotspots were associated with higher average AMA-1 antibody titres than the unstable clusters (optical density [OD] = 1.24, 95% confidence interval [CI] 1.02-1.47 versus OD = 1.1, 95% CI 0.88-1.33) and lower mean ages of febrile malaria episodes (5.8 y, 95% CI 5.6-6.0 versus 5.91 y, 95% CI 5.7-6.1). A falling gradient of febrile malaria incidence was identified in the penumbrae of both hotspots. Hotspots were associated with AMA-1 titres, but not seroconversion rates. In order to target control measures, homesteads at risk of febrile malaria could be predicted by identifying the 20% of homesteads that experienced an episode of febrile malaria during one month in the dry season. That 20% subsequently experienced 65% of all febrile malaria episodes during the following year. A definition based on remote sensing data was 81% sensitive and 63% specific for the stable hotspots of asymptomatic malaria. Conclusions: Hotspots of asymptomatic parasitaemia are stable over time, but hotspots of febrile malaria are unstable. This finding may be because immunity offsets the high rate of febrile malaria that might otherwise result in stable hotspots, whereas unstable hotspots necessarily affect a population with less prior exposure to malaria.

Publication status:PublishedPeer Review status:Peer reviewedVersion:Publisher's version Funder: Wellcome Trust   Notes:Citation: Bejon, P. et al. (2010). 'Stable and unstable malaria hotspots in longitudinal cohort studies in Kenya', PLoS Medicine, 7(7), e1000304. [Available at]. Copyright 2010 Bejon et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Bibliographic Details

Publisher: Public Library of Science

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Host: PLoS Medicinesee more from them

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Issue Date: 2010-July

Copyright Date: 2010

pages:Article: e1000304Identifiers


Issn: 1549-1277

Eissn: 1549-1676

Urn: uuid:43ff9034-5504-446c-96f3-cdf813444bb3 Item Description

Type: Article: post-print;

Language: en

Version: Publisher's versionKeywords: KenyaSubjects: Malaria Tropical medicine Public Health Zoological sciences Tiny URL: ora:4115


Author: Philip Bejon - institutionKilifi KEMRI- Wellcome Trust Collaborative Research Programme, Centre for Geographic Medicine Research



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