The dynamics of
secondary infections with Hymenolepis citelli in mice are described. A primary
infection of one and six cysticercoids for 21 days sensitized CFLP male mice against homologous challenge
infections. Acquired resistance was manifested mainly as
stunting/destrobilation of secondary worms. The severity of
stunting depended on the intensity of the primary
infection. Secondary worms were not expelled more rapidly than primary worms but the protective response retards growth early in challenge
infections. Sensitization of mice for seven days with six or 24 cysticercoids did not confer a measurable protective response, whereas priming by the same regime for 21 days induced a significant protective response. Acquired resistance to challenge waned with time in the absence of the primary worms. The growth and survival of a six-cysticercoid primary
infection was enhanced by the administration of the
immunosuppressant drug cortisone acetate. Worms from
cortisone-treated mice were heavier than those from untreated controls. Acquired resistance to homologous challenge was also partially ablated in
cortisone-treated mice. It is suggested that rejection of primary
infections and
stunting/destrobilation of secondary worms may be immunologically mediated.