Nutrition-parasite interaction.

The interactions between host nutrition and parasitism in ruminants are viewed within a framework that accounts for the allocation of scarce nutrient resources, such as energy and protein, between the various competing body functions of the host. These include functions that are the direct result of parasitism. Since it is proposed that the host gives priority to the reversal of the pathophysiological consequences of parasitism over other body functions, it is to be expected that improved nutrition will always lead to improved resilience. On the other hand, it is proposed that the function of growth, pregnancy and lactation are prioritised over the expression of immunity. Thus, improved nutrition may affect the degree of expression of immunity during these phases. The framework is useful at highlighting areas of future research on host/parasite/nutrition interactions. Its suggestions can account for the observations of the periparturient relaxation of immunity in reproducing females, as well as the reduction in worm burden in small ruminants supplemented with additional protein. Although developed for gastrointestinal nematodes in ruminants, the concepts of the framework should be applicable to the interactions of nutrition in other parasitic diseases.