Inclusion Criteria:  Demonstrated understanding of Cryptosporidium disease, safety measures and transmission risks Good health Ability to communicate well with the Investigator  Exclusion Criteria:  - History of Cryptosporidium infection, gastrointestinal conditions (including diarrheal syndromes, gastroenteritis and gastrointestinal tract surgery), immunodeficiency, infections, significant medical concerns, hypersensitivity to nitazoxanide or other specified antibiotics.  Other protocol-defined inclusion/exclusion criteria may apply.