Cryptosporidiosis, Man

The coccidium Cryptosporidium parvum, the oocysts of which are 4–5 μm in diameter, containing four sporozoites, parasitizes the microvillar border of the intestinal epithelial cells projecting into the lumen. With heavy infections the bile ducts, trachea, and possibly conjunctive may also be involved. In addition to the regular coccidian cycle, thin-walled oocysts are formed that sporulate in the intestine and are a source of superinfection; the thick-walled oocysts pass to the outside and develop four sporozoites. In healthy volunteers, acute infection can be produced by ingestion of 30–300 or more oocysts accompanied by abdominal pain, cramps, diarrhea, and fever lasting for 3–10 days.

C. parvum causes debilitating gastrointestinal illness in humans and other mammals and is a frequent opportunistic pathogen in AIDS patients. Chronic infectionin immunosuppressed patients is associated with flattened villi, resulting from loss of epithelial cells and lack of regeneration...