How does onchocerciasis-related skin and eye disease in Africa depend on cumulative exposure to infection and mass treatment?

<h4>Background</h4>Onchocerciasis (river-blindness) in Africa is targeted for elimination through mass drug administration (MDA) with ivermectin. Onchocerciasis may cause various types of skin and eye disease. Predicting the impact of MDA on onchocercal morbidity is useful for future pol...

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Autores principales:	Natalie V S Vinkeles Melchers, Wilma A Stolk, Michele E Murdoch, Belén Pedrique, Marielle Kloek, Roel Bakker, Sake J de Vlas, Luc E Coffeng
Formato:	article
Lenguaje:	EN
Publicado:	Public Library of Science (PLoS) 2021
Materias:	Arctic medicine. Tropical medicine RC955-962 Public aspects of medicine RA1-1270
Acceso en línea:	https://doaj.org/article/67c3e503d2574b8d9810145e9f64d819
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spelling	oai:doaj.org-article:67c3e503d2574b8d9810145e9f64d8192021-11-25T06:33:08ZHow does onchocerciasis-related skin and eye disease in Africa depend on cumulative exposure to infection and mass treatment?1935-27271935-273510.1371/journal.pntd.0009489https://doaj.org/article/67c3e503d2574b8d9810145e9f64d8192021-06-01T00:00:00Zhttps://doi.org/10.1371/journal.pntd.0009489https://doaj.org/toc/1935-2727https://doaj.org/toc/1935-2735<h4>Background</h4>Onchocerciasis (river-blindness) in Africa is targeted for elimination through mass drug administration (MDA) with ivermectin. Onchocerciasis may cause various types of skin and eye disease. Predicting the impact of MDA on onchocercal morbidity is useful for future policy development. Here, we introduce a new disease module within the established ONCHOSIM model to predict trends over time in prevalence of onchocercal morbidity.<h4>Methods</h4>We developed novel generic model concepts for development of symptoms due to cumulative exposure to dead microfilariae, accommodating both reversible (acute) and irreversible (chronic) symptoms. The model was calibrated to reproduce pre-control age patterns and associations between prevalences of infection, eye disease, and various types of skin disease as observed in a large set of population-based studies. We then used the new disease module to predict the impact of MDA on morbidity prevalence over a 30-year time frame for various scenarios.<h4>Results</h4>ONCHOSIM reproduced observed age-patterns in disease and community-level associations between infection and disease reasonably well. For highly endemic settings with 30 years of annual MDA at 60% coverage, the model predicted a 70% to 89% reduction in prevalence of chronic morbidity. This relative decline was similar with higher MDA coverage and only somewhat higher for settings with lower pre-control endemicity. The decline in prevalence was lowest for mild depigmentation and visual impairment. The prevalence of acute clinical manifestations (severe itch, reactive skin disease) declined by 95% to 100% after 30 years of annual MDA, regardless of pre-control endemicity.<h4>Conclusion</h4>We present generic model concepts for predicting trends in acute and chronic symptoms due to history of exposure to parasitic worm infections, and apply this to onchocerciasis. Our predictions suggest that onchocercal morbidity, in particular chronic manifestations, will remain a public health concern in many epidemiological settings in Africa, even after 30 years of MDA.Natalie V S Vinkeles MelchersWilma A StolkMichele E MurdochBelén PedriqueMarielle KloekRoel BakkerSake J de VlasLuc E CoffengPublic Library of Science (PLoS)articleArctic medicine. Tropical medicineRC955-962Public aspects of medicineRA1-1270ENPLoS Neglected Tropical Diseases, Vol 15, Iss 6, p e0009489 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Arctic medicine. Tropical medicine RC955-962 Public aspects of medicine RA1-1270
spellingShingle	Arctic medicine. Tropical medicine RC955-962 Public aspects of medicine RA1-1270 Natalie V S Vinkeles Melchers Wilma A Stolk Michele E Murdoch Belén Pedrique Marielle Kloek Roel Bakker Sake J de Vlas Luc E Coffeng How does onchocerciasis-related skin and eye disease in Africa depend on cumulative exposure to infection and mass treatment?
description	<h4>Background</h4>Onchocerciasis (river-blindness) in Africa is targeted for elimination through mass drug administration (MDA) with ivermectin. Onchocerciasis may cause various types of skin and eye disease. Predicting the impact of MDA on onchocercal morbidity is useful for future policy development. Here, we introduce a new disease module within the established ONCHOSIM model to predict trends over time in prevalence of onchocercal morbidity.<h4>Methods</h4>We developed novel generic model concepts for development of symptoms due to cumulative exposure to dead microfilariae, accommodating both reversible (acute) and irreversible (chronic) symptoms. The model was calibrated to reproduce pre-control age patterns and associations between prevalences of infection, eye disease, and various types of skin disease as observed in a large set of population-based studies. We then used the new disease module to predict the impact of MDA on morbidity prevalence over a 30-year time frame for various scenarios.<h4>Results</h4>ONCHOSIM reproduced observed age-patterns in disease and community-level associations between infection and disease reasonably well. For highly endemic settings with 30 years of annual MDA at 60% coverage, the model predicted a 70% to 89% reduction in prevalence of chronic morbidity. This relative decline was similar with higher MDA coverage and only somewhat higher for settings with lower pre-control endemicity. The decline in prevalence was lowest for mild depigmentation and visual impairment. The prevalence of acute clinical manifestations (severe itch, reactive skin disease) declined by 95% to 100% after 30 years of annual MDA, regardless of pre-control endemicity.<h4>Conclusion</h4>We present generic model concepts for predicting trends in acute and chronic symptoms due to history of exposure to parasitic worm infections, and apply this to onchocerciasis. Our predictions suggest that onchocercal morbidity, in particular chronic manifestations, will remain a public health concern in many epidemiological settings in Africa, even after 30 years of MDA.
format	article
author	Natalie V S Vinkeles Melchers Wilma A Stolk Michele E Murdoch Belén Pedrique Marielle Kloek Roel Bakker Sake J de Vlas Luc E Coffeng
author_facet	Natalie V S Vinkeles Melchers Wilma A Stolk Michele E Murdoch Belén Pedrique Marielle Kloek Roel Bakker Sake J de Vlas Luc E Coffeng
author_sort	Natalie V S Vinkeles Melchers
title	How does onchocerciasis-related skin and eye disease in Africa depend on cumulative exposure to infection and mass treatment?
title_short	How does onchocerciasis-related skin and eye disease in Africa depend on cumulative exposure to infection and mass treatment?
title_full	How does onchocerciasis-related skin and eye disease in Africa depend on cumulative exposure to infection and mass treatment?
title_fullStr	How does onchocerciasis-related skin and eye disease in Africa depend on cumulative exposure to infection and mass treatment?
title_full_unstemmed	How does onchocerciasis-related skin and eye disease in Africa depend on cumulative exposure to infection and mass treatment?
title_sort	how does onchocerciasis-related skin and eye disease in africa depend on cumulative exposure to infection and mass treatment?
publisher	Public Library of Science (PLoS)
publishDate	2021
url	https://doaj.org/article/67c3e503d2574b8d9810145e9f64d819
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How does onchocerciasis-related skin and eye disease in Africa depend on cumulative exposure to infection and mass treatment?

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