Schistosomiasis: nutritional implications.

Most studies on the interactions of nutrition and schistosomiasis have involved experimental animals. Generally, these studies show that schistosomiasis may be alleviated by severe malnutrition, especially calorie deprivation. However, nutritional modulation of schistosomiasis in experimental animals is observed only when severe deficiencies are induced during the acute disease. Except during overt famine, in humans such severe forms of malnutrition occur mainly in the young, who are not yet exposed to heavy burdens of schistosomal infection. Older individuals, who may be heavily infected, are usually not so severely malnourished. Therefore, the nutritional rehabilitation of severely malnourished children, which should improve immune function, is unlikely to exacerbate the immune-mediated pathogenesis of schistosomal disease. Nutritional interventions can be planned independently of the prevalence or intensity of schistosomiasis in the population. Heavy infection with Schistosoma mansoni can cause both direct nutritional losses and severe disease manifestations. These constitute two important reasons for the administration of mass chemotherapy to the heavily infected segment of a population. Both of these adverse effects can be corrected by a reduction in the intensity of infection; complete cure is not necessary.