Cryptosporidiosis: clinical, epidemiologic, and parasitologic review.

Cryptosporidium, an intestinal protozoan parasite, is a well-known cause of diarrhea in animals but has been recognized only recently as a cause of human disease. Since 1976, 58 cases of cryptosporidiosis in humans have been reported; 18 of the patients had normal immune function, and 40 had various immunologic abnormalities, the most common of which, acquired immune deficiency syndrome (AIDS), occurred in 33 patients. Patients with normal immune function had self-limited diarrhea, but patients with immunologic abnormalities often developed severe, irreversible diarrhea; 22 patients have died. The diagnosis of cryptosporidiosis can now be made noninvasively, but increased diagnostic proficiency has led to little improvement in control or treatment of the disease. Although 23 compounds have been evaluated in experimentally infected animals and 20 drugs have been used in human clinical trials, no effective chemotherapeutic agent for cryptosporidiosis has been identified to date.