Age, Spatial, and Temporal Variations in Hospital Admissions with Malaria in Kilifi County, Kenya: A 25-Year Longitudinal Observational Study.

<h4>Background</h4>Encouraging progress has been seen with reductions in Plasmodium falciparum malaria transmission in some parts of Africa. Reduced transmission might lead to increasing susceptibility to malaria among older children due to lower acquired immunity, and this has implicati...

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Main Authors: Polycarp Mogeni, Thomas N Williams, Gregory Fegan, Christopher Nyundo, Evasius Bauni, Kennedy Mwai, Irene Omedo, Patricia Njuguna, Charles R Newton, Faith Osier, James A Berkley, Laura L Hammitt, Brett Lowe, Gabriel Mwambingu, Ken Awuondo, Neema Mturi, Norbert Peshu, Robert W Snow, Abdisalan Noor, Kevin Marsh, Philip Bejon
Format: Article
Language:English
Published: Public Library of Science (PLoS) 2016-06-01
Series:PLoS Medicine
Online Access:https://doi.org/10.1371/journal.pmed.1002047
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author Polycarp Mogeni
Thomas N Williams
Gregory Fegan
Christopher Nyundo
Evasius Bauni
Kennedy Mwai
Irene Omedo
Patricia Njuguna
Charles R Newton
Faith Osier
James A Berkley
Laura L Hammitt
Brett Lowe
Gabriel Mwambingu
Ken Awuondo
Neema Mturi
Norbert Peshu
Robert W Snow
Abdisalan Noor
Kevin Marsh
Philip Bejon
author_facet Polycarp Mogeni
Thomas N Williams
Gregory Fegan
Christopher Nyundo
Evasius Bauni
Kennedy Mwai
Irene Omedo
Patricia Njuguna
Charles R Newton
Faith Osier
James A Berkley
Laura L Hammitt
Brett Lowe
Gabriel Mwambingu
Ken Awuondo
Neema Mturi
Norbert Peshu
Robert W Snow
Abdisalan Noor
Kevin Marsh
Philip Bejon
author_sort Polycarp Mogeni
collection DOAJ
description <h4>Background</h4>Encouraging progress has been seen with reductions in Plasmodium falciparum malaria transmission in some parts of Africa. Reduced transmission might lead to increasing susceptibility to malaria among older children due to lower acquired immunity, and this has implications for ongoing control strategies.<h4>Methods and findings</h4>We conducted a longitudinal observational study of children admitted to Kilifi County Hospital in Kenya and linked it to data on residence and insecticide-treated net (ITN) use. This included data from 69,104 children aged from 3 mo to 13 y admitted to Kilifi County Hospital between 1 January 1990 and 31 December 2014. The variation in malaria slide positivity among admissions was examined in logistic regression models using the following predictors: location of the residence, calendar time, the child's age, ITN use, and the enhanced vegetation index (a proxy for soil moisture). The proportion of malaria slide-positive admissions declined from 0.56 (95% confidence interval [CI] 0.54-0.58) in 1998 to 0.07 (95% CI 0.06-0.08) in 2009 but then increased again through to 0.24 (95% CI 0.22-0.25) in 2014. Older children accounted for most of the increase after 2009 (0.035 [95% CI 0.030-0.040] among young children compared to 0.22 [95% CI 0.21-0.23] in older children). There was a nonlinear relationship between malaria risk and prevalence of ITN use within a 2 km radius of an admitted child's residence such that the predicted malaria positive fraction varied from ~0.4 to <0.1 as the prevalence of ITN use varied from 20% to 80%. In this observational analysis, we were unable to determine the cause of the decline in malaria between 1998 and 2009, which pre-dated the dramatic scale-up in ITN distribution and use.<h4>Conclusion</h4>Following a period of reduced transmission, a cohort of older children emerged who have increased susceptibility to malaria. Further reductions in malaria transmission are needed to mitigate the increasing burden among older children, and universal ITN coverage is a promising strategy to achieve this goal.
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institution Kabale University
issn 1549-1277
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language English
publishDate 2016-06-01
publisher Public Library of Science (PLoS)
record_format Article
series PLoS Medicine
spelling doaj-art-617a8ff97cc04c669de8300dd53419712025-08-20T03:44:46ZengPublic Library of Science (PLoS)PLoS Medicine1549-12771549-16762016-06-01136e100204710.1371/journal.pmed.1002047Age, Spatial, and Temporal Variations in Hospital Admissions with Malaria in Kilifi County, Kenya: A 25-Year Longitudinal Observational Study.Polycarp MogeniThomas N WilliamsGregory FeganChristopher NyundoEvasius BauniKennedy MwaiIrene OmedoPatricia NjugunaCharles R NewtonFaith OsierJames A BerkleyLaura L HammittBrett LoweGabriel MwambinguKen AwuondoNeema MturiNorbert PeshuRobert W SnowAbdisalan NoorKevin MarshPhilip Bejon<h4>Background</h4>Encouraging progress has been seen with reductions in Plasmodium falciparum malaria transmission in some parts of Africa. Reduced transmission might lead to increasing susceptibility to malaria among older children due to lower acquired immunity, and this has implications for ongoing control strategies.<h4>Methods and findings</h4>We conducted a longitudinal observational study of children admitted to Kilifi County Hospital in Kenya and linked it to data on residence and insecticide-treated net (ITN) use. This included data from 69,104 children aged from 3 mo to 13 y admitted to Kilifi County Hospital between 1 January 1990 and 31 December 2014. The variation in malaria slide positivity among admissions was examined in logistic regression models using the following predictors: location of the residence, calendar time, the child's age, ITN use, and the enhanced vegetation index (a proxy for soil moisture). The proportion of malaria slide-positive admissions declined from 0.56 (95% confidence interval [CI] 0.54-0.58) in 1998 to 0.07 (95% CI 0.06-0.08) in 2009 but then increased again through to 0.24 (95% CI 0.22-0.25) in 2014. Older children accounted for most of the increase after 2009 (0.035 [95% CI 0.030-0.040] among young children compared to 0.22 [95% CI 0.21-0.23] in older children). There was a nonlinear relationship between malaria risk and prevalence of ITN use within a 2 km radius of an admitted child's residence such that the predicted malaria positive fraction varied from ~0.4 to <0.1 as the prevalence of ITN use varied from 20% to 80%. In this observational analysis, we were unable to determine the cause of the decline in malaria between 1998 and 2009, which pre-dated the dramatic scale-up in ITN distribution and use.<h4>Conclusion</h4>Following a period of reduced transmission, a cohort of older children emerged who have increased susceptibility to malaria. Further reductions in malaria transmission are needed to mitigate the increasing burden among older children, and universal ITN coverage is a promising strategy to achieve this goal.https://doi.org/10.1371/journal.pmed.1002047
spellingShingle Polycarp Mogeni
Thomas N Williams
Gregory Fegan
Christopher Nyundo
Evasius Bauni
Kennedy Mwai
Irene Omedo
Patricia Njuguna
Charles R Newton
Faith Osier
James A Berkley
Laura L Hammitt
Brett Lowe
Gabriel Mwambingu
Ken Awuondo
Neema Mturi
Norbert Peshu
Robert W Snow
Abdisalan Noor
Kevin Marsh
Philip Bejon
Age, Spatial, and Temporal Variations in Hospital Admissions with Malaria in Kilifi County, Kenya: A 25-Year Longitudinal Observational Study.
PLoS Medicine
title Age, Spatial, and Temporal Variations in Hospital Admissions with Malaria in Kilifi County, Kenya: A 25-Year Longitudinal Observational Study.
title_full Age, Spatial, and Temporal Variations in Hospital Admissions with Malaria in Kilifi County, Kenya: A 25-Year Longitudinal Observational Study.
title_fullStr Age, Spatial, and Temporal Variations in Hospital Admissions with Malaria in Kilifi County, Kenya: A 25-Year Longitudinal Observational Study.
title_full_unstemmed Age, Spatial, and Temporal Variations in Hospital Admissions with Malaria in Kilifi County, Kenya: A 25-Year Longitudinal Observational Study.
title_short Age, Spatial, and Temporal Variations in Hospital Admissions with Malaria in Kilifi County, Kenya: A 25-Year Longitudinal Observational Study.
title_sort age spatial and temporal variations in hospital admissions with malaria in kilifi county kenya a 25 year longitudinal observational study
url https://doi.org/10.1371/journal.pmed.1002047
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