The effect of amino acid supplementation of the host diet on the growth of the cestode hymenolepis diminuta

ABSTRACT

Although there is evidence to show that in animals on low intakes of protein the parasites flourish better than those animals on normal diets no relationship has been found between parasite growth and intake of protein. The effect of dietary protein on the growth of H. diminuta in the rat was evaluated. The animals were fed diets constant in caloric content but varying in quantity and quality of protein. Removal of casein from the diet, and its replacement by carbohydrate, resulted in a marked increase in the dry weight and nitrogen content of the parasite. Replacement of casein by fat had no effect on worm development, indicating that protein is not a significant factor. Exchange of zein for casein in the diet failed to influence parasite growth and the addition of the amino acids L-tryptophan and L-tryptophan and L-lysine to the meal containing zein in order to balance it nutritional value was also without significant effect on worm growth. These findings indicate that the growth of H. diminuta is uninfluenced by quality of dietary protein. When tryptophan and lysine were fed to the host at times other than those of giving zein, parasite growth was considerably depressed. This effect is unrelated to the quality of protein fed in the rest of the diet, since the depression in worm growth can be demonstrated by their addition to both casein and to protein free diets. Addition of these amino acids to either zein, casein or protein free diets resulted in significant changes in parasite growth, which was sometimes increased and sometimes depressed (AU)