Observations on Certain Phases of Nutrition and Host-Parasite Relations of Hymenolepis diminuta in White Rats

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Abstract
In the preparation of thiamin-free diets for rats, addition of sulfasuxidine had no ill effect on either H. diminuta or on the rat host. As a source of carbohydrate for the worms, sucrose was less favorable than dextrose, and neither permitted as good growth as a mixture of dextrose and starch. Practically complete elimination of thiamin had no adverse effect on the tapeworms. The thiamin content of the intestinal mucosa is reduced by a thiamin-free diet and is increased by parenteral injections of thiamin. A small amount of thiamin persists in the feces even after prolonged elimination of thiamin from the diet, probably contained mostly in the bodies of microorganisms, but this is not increased by parenteral injection of thiamin. The thiamin content of H. diminuta remains fairly constant regardless of the presence or absence of dietary or parenterally injected thiamin in the host. After parenteral injection of radioactive thiamin (containing S35) the thiamin in the tapeworms and in the intestinal mucosa have the same specific activity, indicating that the worms obtain their thiamin from the host. Parasites in the lumen of the intestine receive a great variety of substances, including O2, nitrogenous compounds, and vitamins, by secretion or diffusion from the gut wall or associated glands, and are therefore at least partly independent of these materials in the host''s food. O2 secreted into the lumen, and present mainly at the interface of lumen and mucosa, may be the critical substance needed by the worms, which accounts for the "crowding effect.".