Persistent Cryptosporidium infection in congenitally athymic (nude) mice.

Nude (nu/nu) BALB/c mice and their white (nu/+) littermates were experimentally infected with Cryptosporidium sp. at 6 days of age. In white mice, the infection was transient, but in nude mice a persistent infection developed that was characterized by diarrhea and, occasionally, death. There were villus atrophy and crypt hyperplasia in the small intestine of infected nude and white mice necropsied at 11 days of age. Persistently infected nude mice had, in addition to the above small intestinal lesions, diffuse cystic mucosal hyperplasia and crypt abscesses in the large intestine at 56 days of age. These results suggest that T cells are required for recovery from the Cryptosporidium infection but are not required for epithelial cell loss in cryptosporidiosis. Both nude and white mice appeared to be relatively more resistant to Cryptosporidium infection at 42 days of age than at 6 days of age.