Bovine humoral immune response to Cryptosporidium parvum.

Cryptosporidiosis is a diarrheal disease predominantly affecting cattle and humans. Sera from experimentally infected calves and calves of various ages with no histories of exposure were evaluated for immunoglobulin G to Cryptosporidium parvum. An age-associated increase in immunoglobulin G was present in experimental calves and in calves with no histories of infection from 1 to 3, but not > 3, months of age.