Synergism and antagonism of parasitic diseases and malnutrition.

Malnutrition may appear to increase or decrease the severity of a parasitic disease, but the fundamental mechanisms that influence such synergistic or antagonistic relationship have yet to be identified. Several factors must be considered in an evaluation of possible synergistic or antagonistic relationships. They include the species and virulence of the parasite; the nutritional requirements of the parasite; the severity, duration, and type of malnutrition in the host; and lastly, the competence of immune mechanisms and other resistance factors in the host. Because the immune system may be impaired by malnutrition, fails to provide protection against most parasitic infections, and has a known propensity for producing harmful as well as beneficial responses, the immunological functions of the host are undoubtedly key indicators of whether malnutrition will cause an increase or a decrease in the severity f a parasitic disease.