Ascariasis and childhood malnutrition.

In 1968, the World Health Organization published a volume entitled Interactions of Nutrition and Infection (SCRIMSHAW et al., 1968). The preface opened with these words: 'That malnutrition increases susceotibilitv to infectious disease seems a reasonable assumption, and clinical observation in areas where malnutrition is common has generally lent support to this belief. Equally reasonable is the supposition that infectious diseases have an adverse effect on the nutritional state.' The authors' analysis of the interactions between parasitism and nutrition laid the foundation for much experimental and clinical research and for many investigations in communities where parasitic disease is endemic and where malnutrition prevails. They stimulated a vigorous debate between those who concurred with the notion that parasitic infections impair human nutritional status and those who were somewhat sceptical of the evidence and the manner in which it was being obtained. Not surprisingly, the proposed role of Ascaris Zumbricoides as a determinant of childhood nutritional status was discussed extensively. Was Tyson right? Does A. lumbricoides usually trouble children? At least 4 general types of complex interaction appear to link helminth infection and host nutrition. Firstly, many types of helminth are transmitted in the host's diet often as-unseen contaminants of a range of foodstuffs (COOMBS & CROMPTON. 1991). Secondlv, in addition to obtaining food and energy for themselves, all hosts at some time provide nutrients and energy for their hel-minths either directly from thyme and digestion products in the gut or indirectly, and more usually, at the expense of their own tissues and metabolites. Thirdly, host food intake, digestion, absorption, metabolism, growth and development may be impaired to varying degrees during the course of a helminth infection, Fourthly, the population biology, growth, survival and reproduction of helminths may be altered in association with the aualitv and quantity *of food obtained and metabolized by the host (BUNDY & GOLDEN. 1987: CROMPTON. 19871. These'general effects do not occur'in any sequence; they are interrelated and often unpredictable in their extent or significance. The situation is made even more complex by the fact that the host's resistance to infection is affected by nutritional factors (CHANDRA & NEWBERNE, 1977; CHANDRA, 1980) and some of the agents of the immune response, particularly cytokines released during infection (KLASING, 1988), influence nutritional status. Direct evidence for the existence of interactions between helminth infections and host nutrition is based overwhelminalv on the results of controlled exoeriments with laboratory rodents (PARSHAD et al. …