The establishment, growth, survival and distribution olHymenolepis muris-sylvaticaem different laboratory animals (Wistar rats, golden hamsters, CFLP and NMRI mice) after oral infection and surgical transplantation were determined.Worms that establish in CFLP and NMRI mice grow exponentially but are rejected at different times p.i. depending on the strain of mice and mode of infection. Only in golden hamsters willH. muris-sylvaticaedevelop to a mature worm; in rats there is no growth at all. Worms of all sizes are found in the posterior half of the small intestine in rats and both strains of mice; in hamsters the worms are recovered more anteriorly.

When mice were treated with 1–25 mg cortisone acetate thrice weekly, recovery of Hymenolepis murissylvaticae was significantly higher than in untreated controls, both in oral infections with six cysticercoids and surgical transplantations of one 7-day or 8-day-old worm. Cortisone treatment also resulted in the worms being located more anteriorly in the small intestine. Evidence of an immunological response against the tapeworm in the intestine is given by: (a) an accelerated rejection of a secondary oral cysticercoid infection and a significant difference of the dry weights of the worms recovered on day 10 in CFLP mice; (b) an accelerated rejection of a secondary surgical infection on days 4 and 6 in CFLP mice and on days 3 and 4 in NMRI mice; (c) an accelerated rejection of a secondary surgical infection given 3 and 6 months after the primary immunizing infection in SWlSS-albino mice.

Hymenolepis murissylvatici elicits a humoral response in serum and in the intestine of the mouse from which it is immunologically rejected. In serum, significant differences were recorded 3 days after reinfection, while in intestinal lavages it takes place from day 9 after reinfection. In serum the response is largely the result of IgG and IgM antibodies whereas in the intestine, IgA is the most abundant antibody. Although specific IgE could not be demonstrated in serum, it was present in intestinal lavages, although rather late (i.e. day 14 after reinfection). Treatment of young worms in vitro both with immune serum or intestinal lavages had no apparent effect on their viability. Immune serum produced a complement independent precipitation on the surface of the worms in vitro. This reaction did not affect viability or infectivity of the parasite, as demonstrated by the successful implantation of treated worms in recipient mice. The above-mentioned results, together with the knowledge that the Hymenolepis model has no tissue stages and causes no tissue damage, make it probable that further study of this model will reveal some specific intestinal immunological reactions.

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