Malnutrition and parasitic helminth infections

The Global Burden of Disease caused by the 3 major intestinal nematodes is an estimated 22.1 million disability-adjusted life-years (DALYs) lost for h ookworm, 10.5 million for Ascaris lumbricoides, 6.4 million for Trichuris t richiura, and 39.0 million for the three infections combined (as compared w ith malaria at 35.7 million) (World Bank, 1993; Chan et al. 1994); these fi gures illustrate why some scarce health care resources must be used for the ir control. Strongyloides stercoralis is the fourth most important intestin al worm infection ; its nutritional implications are discussed, and the fac t that its geographic distribution needs further study is emphasized. Mecha nisms underlying the malnutrition induced by intestinal helminths are descr ibed, Anorexia, which can decrease intake of all nutrients in tropical popu lations on marginal diets, is likely to be the most important in terms of m agnitude and the probable major mechanism by which intestinal nematodes inh ibit growth and development. We present a revised and expanded conceptual f ramework for how parasites cause/aggravate malnutrition and retard developm ent in endemic areas. Specific negative effects that a wide variety of para sites may have on gastrointestinal physiology are presented. The synergism between Trichuris and Campylobacter, intestinal inflammation and growth fai lure, and new studies showing that hookworm inhibits growth and promotes an aemia in preschool (as well as school-age) children are presented. We concl ude by presenting rationales and evidence to justify ensuring the widest po ssible coverage for preschool-age children and girls and women of childbear ing age in intestinal parasite control programmes, in order to prevent morb idity and mortality in general and specifically to help decrease the viciou s intergenerational cycle of growth failure (of low-birth-weight/intrauteri ne growth retardation and stunting) that entraps infants, children and girl s and women of reproductive age in developing areas.