From high to low malaria transmission in Zanzibar—challenges and opportunities to achieve elimination
BACKGROUND: Substantial global progress in the control of malaria in recent years has led to increased commitment to its potential elimination. Whether this is possible in high transmission areas of sub-Saharan Africa remains unclear. Zanzibar represents a unique case study of such attempt, where mo...
Autores principales: | , , , , , , , , , , , , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
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BioMed Central
2019
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6341737/ https://www.ncbi.nlm.nih.gov/pubmed/30665398 http://dx.doi.org/10.1186/s12916-018-1243-z |
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author | Björkman, A. Shakely, D. Ali, A. S. Morris, U. Mkali, H. Abbas, A. K. Al-Mafazy, A-W Haji, K. A. Mcha, J. Omar, R. Cook, J. Elfving, K. Petzold, M. Sachs, M. C. Aydin-Schmidt, B. Drakeley, C. Msellem, M. Mårtensson, A. |
author_facet | Björkman, A. Shakely, D. Ali, A. S. Morris, U. Mkali, H. Abbas, A. K. Al-Mafazy, A-W Haji, K. A. Mcha, J. Omar, R. Cook, J. Elfving, K. Petzold, M. Sachs, M. C. Aydin-Schmidt, B. Drakeley, C. Msellem, M. Mårtensson, A. |
author_sort | Björkman, A. |
collection | PubMed |
description | BACKGROUND: Substantial global progress in the control of malaria in recent years has led to increased commitment to its potential elimination. Whether this is possible in high transmission areas of sub-Saharan Africa remains unclear. Zanzibar represents a unique case study of such attempt, where modern tools and strategies for malaria treatment and vector control have been deployed since 2003. METHODS: We have studied temporal trends of comprehensive malariometric indices in two districts with over 100,000 inhabitants each. The analyses included triangulation of data from annual community-based cross-sectional surveys, health management information systems, vital registry and entomological sentinel surveys. RESULTS: The interventions, with sustained high-community uptake, were temporally associated with a major malaria decline, most pronounced between 2004 and 2007 and followed by a sustained state of low transmission. In 2015, the Plasmodium falciparum community prevalence of 0.43% (95% CI 0.23–0.73) by microscopy or rapid diagnostic test represented 96% reduction compared with that in 2003. The P. falciparum and P. malariae prevalence by PCR was 1.8% (95% CI 1.3–2.3), and the annual P. falciparum incidence was estimated to 8 infections including 2.8 clinical episodes per 1000 inhabitants. The total parasite load decreased over 1000-fold (99.9%) between 2003 and 2015. The incidence of symptomatic malaria at health facilities decreased by 94% with a trend towards relatively higher incidence in age groups > 5 years, a more pronounced seasonality and with reported travel history to/from Tanzania mainland as a higher risk factor. All-cause mortality among children < 5 years decreased by 72% between 2002 and 2007 mainly following the introduction of artemisinin-based combination therapies whereas the main reduction in malaria incidence followed upon the vector control interventions from 2006. Human biting rates decreased by 98% with a major shift towards outdoor biting by Anopheles arabiensis. CONCLUSIONS: Zanzibar provides new evidence of the feasibility of reaching uniquely significant and sustainable malaria reduction (pre-elimination) in a previously high endemic region in sub-Saharan Africa. The data highlight constraints of optimistic prognostic modelling studies. New challenges, mainly with outdoor transmission, a large asymptomatic parasite reservoir and imported infections, require novel tools and reoriented strategies to prevent a rebound effect and achieve elimination. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12916-018-1243-z) contains supplementary material, which is available to authorized users. |
format | Online Article Text |
id | pubmed-6341737 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2019 |
publisher | BioMed Central |
record_format | MEDLINE/PubMed |
spelling | pubmed-63417372019-01-24 From high to low malaria transmission in Zanzibar—challenges and opportunities to achieve elimination Björkman, A. Shakely, D. Ali, A. S. Morris, U. Mkali, H. Abbas, A. K. Al-Mafazy, A-W Haji, K. A. Mcha, J. Omar, R. Cook, J. Elfving, K. Petzold, M. Sachs, M. C. Aydin-Schmidt, B. Drakeley, C. Msellem, M. Mårtensson, A. BMC Med Research Article BACKGROUND: Substantial global progress in the control of malaria in recent years has led to increased commitment to its potential elimination. Whether this is possible in high transmission areas of sub-Saharan Africa remains unclear. Zanzibar represents a unique case study of such attempt, where modern tools and strategies for malaria treatment and vector control have been deployed since 2003. METHODS: We have studied temporal trends of comprehensive malariometric indices in two districts with over 100,000 inhabitants each. The analyses included triangulation of data from annual community-based cross-sectional surveys, health management information systems, vital registry and entomological sentinel surveys. RESULTS: The interventions, with sustained high-community uptake, were temporally associated with a major malaria decline, most pronounced between 2004 and 2007 and followed by a sustained state of low transmission. In 2015, the Plasmodium falciparum community prevalence of 0.43% (95% CI 0.23–0.73) by microscopy or rapid diagnostic test represented 96% reduction compared with that in 2003. The P. falciparum and P. malariae prevalence by PCR was 1.8% (95% CI 1.3–2.3), and the annual P. falciparum incidence was estimated to 8 infections including 2.8 clinical episodes per 1000 inhabitants. The total parasite load decreased over 1000-fold (99.9%) between 2003 and 2015. The incidence of symptomatic malaria at health facilities decreased by 94% with a trend towards relatively higher incidence in age groups > 5 years, a more pronounced seasonality and with reported travel history to/from Tanzania mainland as a higher risk factor. All-cause mortality among children < 5 years decreased by 72% between 2002 and 2007 mainly following the introduction of artemisinin-based combination therapies whereas the main reduction in malaria incidence followed upon the vector control interventions from 2006. Human biting rates decreased by 98% with a major shift towards outdoor biting by Anopheles arabiensis. CONCLUSIONS: Zanzibar provides new evidence of the feasibility of reaching uniquely significant and sustainable malaria reduction (pre-elimination) in a previously high endemic region in sub-Saharan Africa. The data highlight constraints of optimistic prognostic modelling studies. New challenges, mainly with outdoor transmission, a large asymptomatic parasite reservoir and imported infections, require novel tools and reoriented strategies to prevent a rebound effect and achieve elimination. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12916-018-1243-z) contains supplementary material, which is available to authorized users. BioMed Central 2019-01-22 /pmc/articles/PMC6341737/ /pubmed/30665398 http://dx.doi.org/10.1186/s12916-018-1243-z Text en © The Author(s). 2019 Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. |
spellingShingle | Research Article Björkman, A. Shakely, D. Ali, A. S. Morris, U. Mkali, H. Abbas, A. K. Al-Mafazy, A-W Haji, K. A. Mcha, J. Omar, R. Cook, J. Elfving, K. Petzold, M. Sachs, M. C. Aydin-Schmidt, B. Drakeley, C. Msellem, M. Mårtensson, A. From high to low malaria transmission in Zanzibar—challenges and opportunities to achieve elimination |
title | From high to low malaria transmission in Zanzibar—challenges and opportunities to achieve elimination |
title_full | From high to low malaria transmission in Zanzibar—challenges and opportunities to achieve elimination |
title_fullStr | From high to low malaria transmission in Zanzibar—challenges and opportunities to achieve elimination |
title_full_unstemmed | From high to low malaria transmission in Zanzibar—challenges and opportunities to achieve elimination |
title_short | From high to low malaria transmission in Zanzibar—challenges and opportunities to achieve elimination |
title_sort | from high to low malaria transmission in zanzibar—challenges and opportunities to achieve elimination |
topic | Research Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6341737/ https://www.ncbi.nlm.nih.gov/pubmed/30665398 http://dx.doi.org/10.1186/s12916-018-1243-z |
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