Developmental physiology of cestodes. V. Effects of vitamin deficient diets and host coprophagy prevention on development on Hymenolepis diminuta.

Effects of B vitamin deficient diets on Hymenolepis diminuta were studied. The worms were markedly affected by a diet deficient in all B vitamins only when host coprophagy was prevented, but some effects were noted in worms from hosts where coprophagy was allowed. Very few worms could establish themselves in coprophagy-prevented rats on the B vitamin deficient diet, and growth in weight, length, and proglottid numbers, and proglottid differentiation were severely impaired. Further investigation showed that the dietary absence of pyridoxine was responsible for the foregoing effects. Pyridoxine deficient worms exhibited abnormalities similar to those found in B vitamin deficient worms. The abnormalities were partially mitigated when rats were injected with 10 ,ug pyridoxine HCl/day while being fed pyridoxine deficient diets. The average size of the worms under these conditions was about half that of controls. However, if 10 jig pyridoxine HCl/day was provided in the diet, or if larger amounts of pyridoxine HC1 were injected, worm size was equal to controls. The results imply that vitamin B6 may be a growth factor for H. diminuta, and the worms may obtain the vitamin from the exocrino-enteric circulation when it is absent from the ingesta. Little is known about the vitamin requirements of any cestode, although the requirements of H. diminuta have received the most attention. Hager (1941) observed, over a period of several months, that a diet deficient in thiamine had no effect on the egg production of H. diminuta, but a diet deficient in all B vitamins, supplemented with thiamine, greatly decreased the egg production. These experiments were repeated by Chandler (1943) and Addis and Chandler (1944) except that they noted the effects on numbers of worms recovered and the total length of the worms in 14-, 28-, and 30-day infections. They reported that diets deficient in thiamine, or diets deficient in vitamins A, D, and E, supplemented with thiamine, stunted the worms, but only in female rats. Addis and Chandler (1946) later found that the dietary presence of none of the B vitamins (niacin, pyridoxine, pantothenic acid, riboflavin, biotin, p-aminobenzoic acid, inositol, choline, and folic acid), either collectively or individually, would support normal growth in the worms. They concluded that some factor (s) in yeast, other than the vitamins they included, was * This investigation was supported by Grants AI-06153 and 5 TOI AI-226 from the NIH, U. S. Public Health Service. t Present address: The Rockefeller University, New York, New York 10021. Received for publication 2 May 1969. necessary for normal growth and establishment of H. diminuta because their complete diet had contained yeast as the B vitamin source. Subsequently, Beck (1951) reported that "B vitamin deficient diets" decreased egg production in H. diminuta both in male and female rats. The rats on the "B vitamin deficient diet" received choline, thiamine, riboflavin, pyridoxine, calcium pantothenate, and p-aminobenzoic acid each day in excess of the daily requirement. Whether the vitamins were given by mouth or by injection was not stated. Under the conditions used by the foregoing investigators, H. diminuta did not require vitamins A, D, E, or thiamine in the host diet; however, the situation with respect to the other B vitamins was equivocal since dried brewer's yeast was included in their diets as the complete B vitamin source. Hence, elimination of B vitamins from the host diet was accompanied by a major dietary change since brewer's yeast comprised about 9% of the diet. Although the full implications of such a dietary change on H. diminuta have not been investigated, the data of Addis and Chandler (1946) indicated that the absence of yeast, replaced by the available B vitamins, resulted in a 52% reduction in length of the worms. The absence of synthetic vitamins from the yeast-free diet had no consistent effects on growth of H. diminuta when compared to the correct control diet, i.e., one in which