Progress in reducing malaria burden in Africa may have had the paradoxical effect of increasing transmission among older children in recent years, according to research published this week in PLOS Medicine. The 25-year observational study, by Polycarp Mogeni, of the KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya, and colleagues, analyzed malaria screening data from pediatric emergency admissions to Kilifi County Hospital between 1990 and 2014. Over this time, 69,104 children aged from 3 months to 13 years old who were admitted had malaria screening data available. The proportion of admissions found positive for malaria decreased from a high of 56% in 1998 to a low of 7% in 2009, but then rose again to 24% in 2014. The recent increases in infections coincided with a shift in burden from younger to older children, and the researchers found children that lived in areas with high usage of insecticide treated bednets (ITNs) were less likely to present with malaria than children who lived in areas with low usage of ITNs. The researchers suggest that the upswing of malaria transmission among older children following a period of low malaria transmission may be due to decreased acquired immunity due to the fact that these children were less likely to have been exposed to malaria early in life.
The authors note that varying levels of access to care and bednet use may have introduced bias, and that the data were taken from a single geographic setting. However, the authors say the findings suggest that malaria elimination will require continued-- and increasing-- vigilance: "As countries and regions make progress in malaria control, maintaining control measures will be essential: in fact, further progress will be required to offset the increasing rates of malaria in older children."
In an accompanying Perspective, Lorenz von Seidlein and Jakob Knudsen discuss the hurdle that decreased immunity presents for malaria elimination strategies, and potential strategies for improving ITN usage in high-transmission settings.
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Research Article
Funding:
The work was supported by core funding from the Wellcome Trust. RWS, AN, and TNW are supported by the Wellcome Trust as Principal Research Fellow (#079080/#103602),Intermediate Fellow (#095127) and Senior Fellow (#091758), respectively, and PB is supported by the UK Medical Research Council (MRC) and the UK Department for International Development (DFID) under the MRC/DFID Concordat agreement. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests:
AN serves on the PLOS Medicine Editorial Board.
Citation:
Mogeni P, Williams TN, Fegan G, Nyundo C, Bauni E, Mwai K, et al. (2016) Age, Spatial, and Temporal Variations in Hospital Admissions with Malaria in Kilifi County, Kenya: A 25-Year Longitudinal Observational Study. PLoS Med 13(6): e1002047. doi:10.1371/journal.pmed.1002047
Author Affiliations:
KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
Imperial College London, London, United Kingdom
Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, CCVTM, Oxford, United Kingdom
Johns Hopkins Bloomberg School of Public Health, Department of International Health, Baltimore, Maryland, United States of America
Spatial Health Metrics Group, Kenya Medical Research Institute/Wellcome Trust Research Programme, Nairobi, Kenya
IN YOUR COVERAGE PLEASE USE THIS URL TO PROVIDE ACCESS TO THE FREELY AVAILABLE PAPER: http://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1002047
Contact:
Polycarp Mogeni Centre for Geographic Medicine Research Coast Bioscience Bofa-Opposite Kilifi County Hospital Kilifi, Coast 80108 KENYA +254710792334 PMogeni@kemri-wellcome.org
Perspective Article
Funding: No funding was obtained for this work.
Competing Interests:
LvS receives a stipend as a specialty consulting editor for PLOS Medicine and serves on the journal's editorial board. The authors have declared that no other competing interests exist.
Citation:
von Seidlein L, Knudsen J (2016) Malaria Epidemiology in Kilifi, Kenya during the 21st Century: What Next? PLoS Med 13(6): e1002048. doi:10.1371/journal.pmed.1002048
Author Affiliations:
Mahidol-Oxford Tropical Medicine Research Unit (MORU), Mahidol, Thailand
The Royal Danish Academy of Fine Arts, Schools of Architecture, Design and Conservation, Copenhagen, Denmark
IN YOUR COVERAGE PLEASE USE THIS URL TO PROVIDE ACCESS TO THE FREELY AVAILABLE PAPER: http://www.plosmedicine.org/article/info%3Adoi%2F10.1371%2Fjournal.pmed.1002048
Journal
PLoS Medicine