Observations on the Digestion of the Shells of the Eggs of Taenia Taeniaeformis

Abstract

From time to time reports (1, 2, 3, 4) have been published from this laboratory on the experimental production of Cysticercus tumors of the liver of rats by feeding these animals cat feces containing the eggs of Taenia taeniaeformis (crassicollis). Following the ingestion of the eggs by the rats, the shells of the eggs are digested away and the freed oncospheres gain access to the blood vessels of the intestinal wall and are carried to the liver. In their passage from the intestine of the cat to the liver of the rat the larvae may carry with them bacteria which may survive and multiply in the liver tissues. What rôle, if any, these bacteria play in the reactions of the rat's liver has not been determined. The presence of the oncosphere in the liver stimulates a proliferative tissue reaction of the host which terminates in the formation of a fibrous-walled cyst about the larva. In other publications (5, 6) it has been shown that Taenia larvae of an early stage of development, when transplanted from the livers of rats to the groins of other rats, may grow and induce the formation of fibrous cyst walls in the subcutaneous tissues. Eight to 27 months after the rats were infested the walls of some of the parasitic cysts, both in the liver and in the groin, showed early sarcomatous changes or were partially or completely transformed into tumors, usually sarcomata.