The role of nutrition in integrated programs to control neglected tropical diseases

The fundamental basis of the relationship between an infectious organism and its host is nutritional because the host is the source of all nutrients needed by the organism for maintenance, growth, and reproduction [1]. But the impact of obligate parasites on the nutritional status of a host is not due just to a requirement for nutrients, it is due mainly to the host's responses to infection which lead to an increased metabolic rate, loss of appetite, immune responses, and pathological changes in tissues [2]. Although some of these reactions may be protective to a degree during acute infection, during repeated or chronic infection they can cause the host to become undernourished, especially if the diet is already poor. Undernutrition also increases susceptibility to infection and increases the severity of disease which can lead to a downward spiral of increasing undernutrition and repeated or persistent disease. In this opinion article we argue that breaking out of that spiral requires not just treating disease but treating undernutrition as well, and that nutrition needs to become an important component of integrated programs to control neglected tropical diseases (NTDs).The relatively new classification by the World Health Organization (WHO) of 17 diseases as 'NTDs' includes eight that are caused by at least 23 species of parasitic worms or helminths [3]. The five NTDs of major interest for control efforts listed in Table 1 (intestinal worms, lymphatic filariasis, onchocerciasis, schistosomiasis, and trachoma) have been identified because of the large numbers of people infected, but mainly because there are safe, inexpensive, single-dose drugs to treat them by mass chemotherapy [4]. The hope is to make drugs available free or at a very low cost and deliver them in 'community directed treatment' using a model developed during onchocerciasis control programs [5] or by school teachers to their pupils [6,7]. Mass treatment serves also to decrease transmission by killin