The effect of alpha+-thalassaemia on the incidence of malaria and other diseases in children living on the coast of Kenya.

<h4>Background</h4>The alpha-thalassaemias are the commonest genetic disorders of humans. It is generally believed that this high frequency reflects selection through a survival advantage against death from malaria; nevertheless, the epidemiological description of the relationships betwe...

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Autores principales:	Sammy Wambua, Tabitha W Mwangi, Moses Kortok, Sophie M Uyoga, Alex W Macharia, Jedidah K Mwacharo, David J Weatherall, Robert W Snow, Kevin Marsh, Thomas N Williams
Formato:	article
Lenguaje:	EN
Publicado:	Public Library of Science (PLoS) 2006
Materias:	Medicine R
Acceso en línea:	https://doaj.org/article/a8c6f8bc992443bd84605921228b2e50
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spelling	oai:doaj.org-article:a8c6f8bc992443bd84605921228b2e502021-12-02T19:55:58ZThe effect of alpha+-thalassaemia on the incidence of malaria and other diseases in children living on the coast of Kenya.1549-12771549-167610.1371/journal.pmed.0030158https://doaj.org/article/a8c6f8bc992443bd84605921228b2e502006-05-01T00:00:00Zhttps://doi.org/10.1371/journal.pmed.0030158https://doaj.org/toc/1549-1277https://doaj.org/toc/1549-1676<h4>Background</h4>The alpha-thalassaemias are the commonest genetic disorders of humans. It is generally believed that this high frequency reflects selection through a survival advantage against death from malaria; nevertheless, the epidemiological description of the relationships between alpha-thalassaemia, malaria, and other common causes of child mortality remains incomplete.<h4>Methods and findings</h4>We studied the alpha+-thalassaemia-specific incidence of malaria and other common childhood diseases in two cohorts of children living on the coast of Kenya. We found no associations between alpha+-thalassaemia and the prevalence of symptomless Plasmodium falciparum parasitaemia, the incidence of uncomplicated P. falciparum disease, or parasite densities during mild or severe malaria episodes. However, we found significant negative associations between alpha+-thalassaemia and the incidence rates of severe malaria and severe anaemia (haemoglobin concentration < 50 g/l). The strongest associations were for severe malaria anaemia (> 10,000 P. falciparum parasites/mul) and severe nonmalaria anaemia; the incidence rate ratios and 95% confidence intervals (CIs) for alpha+-thalassaemia heterozygotes and homozygotes combined compared to normal children were, for severe malaria anaemia, 0.33 (95% CI, 0.15,0.73; p = 0.006), and for severe nonmalaria anaemia, 0.26 (95% CI, 0.09,0.77; p = 0.015).<h4>Conclusions</h4>Our observations suggest, first that selection for alpha+-thalassaemia might be mediated by a specific effect against severe anaemia, an observation that may lead to fresh insights into the aetiology of this important condition. Second, although alpha+-thalassaemia is strongly protective against severe and fatal malaria, its effects are not detectable at the level of any other malaria outcome; this result provides a cautionary example for studies aimed at testing malaria interventions or identifying new malaria-protective genes.Sammy WambuaTabitha W MwangiMoses KortokSophie M UyogaAlex W MachariaJedidah K MwacharoDavid J WeatherallRobert W SnowKevin MarshThomas N WilliamsPublic Library of Science (PLoS)articleMedicineRENPLoS Medicine, Vol 3, Iss 5, p e158 (2006)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R
spellingShingle	Medicine R Sammy Wambua Tabitha W Mwangi Moses Kortok Sophie M Uyoga Alex W Macharia Jedidah K Mwacharo David J Weatherall Robert W Snow Kevin Marsh Thomas N Williams The effect of alpha+-thalassaemia on the incidence of malaria and other diseases in children living on the coast of Kenya.
description	<h4>Background</h4>The alpha-thalassaemias are the commonest genetic disorders of humans. It is generally believed that this high frequency reflects selection through a survival advantage against death from malaria; nevertheless, the epidemiological description of the relationships between alpha-thalassaemia, malaria, and other common causes of child mortality remains incomplete.<h4>Methods and findings</h4>We studied the alpha+-thalassaemia-specific incidence of malaria and other common childhood diseases in two cohorts of children living on the coast of Kenya. We found no associations between alpha+-thalassaemia and the prevalence of symptomless Plasmodium falciparum parasitaemia, the incidence of uncomplicated P. falciparum disease, or parasite densities during mild or severe malaria episodes. However, we found significant negative associations between alpha+-thalassaemia and the incidence rates of severe malaria and severe anaemia (haemoglobin concentration < 50 g/l). The strongest associations were for severe malaria anaemia (> 10,000 P. falciparum parasites/mul) and severe nonmalaria anaemia; the incidence rate ratios and 95% confidence intervals (CIs) for alpha+-thalassaemia heterozygotes and homozygotes combined compared to normal children were, for severe malaria anaemia, 0.33 (95% CI, 0.15,0.73; p = 0.006), and for severe nonmalaria anaemia, 0.26 (95% CI, 0.09,0.77; p = 0.015).<h4>Conclusions</h4>Our observations suggest, first that selection for alpha+-thalassaemia might be mediated by a specific effect against severe anaemia, an observation that may lead to fresh insights into the aetiology of this important condition. Second, although alpha+-thalassaemia is strongly protective against severe and fatal malaria, its effects are not detectable at the level of any other malaria outcome; this result provides a cautionary example for studies aimed at testing malaria interventions or identifying new malaria-protective genes.
format	article
author	Sammy Wambua Tabitha W Mwangi Moses Kortok Sophie M Uyoga Alex W Macharia Jedidah K Mwacharo David J Weatherall Robert W Snow Kevin Marsh Thomas N Williams
author_facet	Sammy Wambua Tabitha W Mwangi Moses Kortok Sophie M Uyoga Alex W Macharia Jedidah K Mwacharo David J Weatherall Robert W Snow Kevin Marsh Thomas N Williams
author_sort	Sammy Wambua
title	The effect of alpha+-thalassaemia on the incidence of malaria and other diseases in children living on the coast of Kenya.
title_short	The effect of alpha+-thalassaemia on the incidence of malaria and other diseases in children living on the coast of Kenya.
title_full	The effect of alpha+-thalassaemia on the incidence of malaria and other diseases in children living on the coast of Kenya.
title_fullStr	The effect of alpha+-thalassaemia on the incidence of malaria and other diseases in children living on the coast of Kenya.
title_full_unstemmed	The effect of alpha+-thalassaemia on the incidence of malaria and other diseases in children living on the coast of Kenya.
title_sort	effect of alpha+-thalassaemia on the incidence of malaria and other diseases in children living on the coast of kenya.
publisher	Public Library of Science (PLoS)
publishDate	2006
url	https://doaj.org/article/a8c6f8bc992443bd84605921228b2e50
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The effect of alpha+-thalassaemia on the incidence of malaria and other diseases in children living on the coast of Kenya.

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