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Malnutrition and parasitic helminth infections
- L.S. STEPHENSON, M.C. LATHAM, E.A. OTTESEN
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- Journal:
- Parasitology / Volume 121 / Issue S1 / October 2000
- Published online by Cambridge University Press:
- 15 June 2001, pp. S23-S38
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- Article
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The Global Burden of Disease caused by the 3 major intestinal nematodes is an estimated 22·1million disability-adjusted life-years (DALYs) lost for hookworm, 10·5million for Ascaris lumbricoides, 6·4million for Trichuris trichiura, and 39·0million for the three infections combined (as compared with malaria at 35·7million) (World Bank, 1993; Chan et al. 1994); these figures illustrate why some scarce health care resources must be used for their control. Strongyloides stercoralis is the fourth most important intestinal worm infection; its nutritional implications are discussed, and the fact that its geographic distribution needs further study is emphasized. Mechanisms underlying the malnutrition induced by intestinal helminths are described. Anorexia, which can decrease intake of all nutrients in tropical populations on marginal diets, is likely to be the most important in terms of magnitude and the probable major mechanism by which intestinal nematodes inhibit growth and development. We present a revised and expanded conceptual framework for how parasites cause/aggravate malnutrition and retard development in endemic areas. Specific negative effects that a wide variety of parasites may have on gastrointestinal physiology are presented. The synergism between Trichuris and Campylobacter, intestinal inflammation and growth failure, and new studies showing that hookworm inhibits growth and promotes anaemia in preschool (as well as school-age) children are presented. We conclude by presenting rationales and evidence to justify ensuring the widest possible coverage for preschool-age children and girls and women of childbearing age in intestinal parasite control programmes, in order to prevent morbidity and mortality in general and specifically to help decrease the vicious intergenerational cycle of growth failure (of low-birth-weight/intrauterine growth retardation and stunting) that entraps infants, children and girls and women of reproductive age in developing areas.
Global malnutrition
- L.S. STEPHENSON, M.C. LATHAM, E.A. OTTESEN
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- Journal:
- Parasitology / Volume 121 / Issue S1 / October 2000
- Published online by Cambridge University Press:
- 15 June 2001, pp. S5-S22
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- Article
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The four most important forms of malnutrition worldwide (protein-energy malnutrition, iron deficiency and anaemias (IDA), vitamin A deficiency (VAD), and iodine deficiency disorders (IDD)) are examined below in terms of their global and regional prevalences, the age and gender groups most affected, their clinical and public health consequences, and, especially, the recent progress in country and regional quantitation and control. Zinc deficiency, with its accompanying diminished host resistance and increased susceptibility to infections, is also reviewed. WHO estimates that malnutrition (underweight) was associated with over half of all child deaths in developing countries in 1995. The prevalence of stunting in developing countries is expected to decline from 36% in 1995 to 32·5% in 2000; the numbers of children affected (excluding China) are expected to decrease from 196·59millions to 181·92millions. Stunting affects 48% of children in South Central Asia, 48% in Eastern Africa, 38% in South Eastern Asia, and 13–24% in Latin America. IDA affects about 43% of women and 34% of men in developing countries and usually is most serious in pregnant women and children, though non-pregnant women, the elderly, and men in hookworm-endemic areas also comprise groups at risk. Clinical VAD affects at least 2·80million preschool children in over 60 countries, and subclinical VAD is considered a problem for at least 251millions; school-age children and pregnant women are also affected. Globally about 740million people are affected by goitre, and over two billions are considered at risk of IDD. However, mandatory salt iodisation in the last decade in many regions has decreased dramatically the percentage of the population at risk. Two recent major advances in understanding the global importance of malnutrition are (1) the data of 53 countries that links protein-energy malnutrition (assessed by underweight) directly to increased child mortality rates, and (2) the outcome in 6 of 8 large vitamin A supplementation trials showing decreases of 20–50% in child mortality.
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