Cryptosporidiosis is one of the main causes of persistent diarrhea in the developed world. It is caused by the presence of Cryptosporidium parvum oocysts in the gastrointestinal tract. This parasite is known to be highly pathogenic and its infectious stage is transmitted by fecal-oral contact. It is also an opportunistic pathogen found in immunocompromised patients.
The symptoms of cryptosporidiosis are watery diarrhea, stomach cramps, weight loss, nausea, and fever. In industrialized countries, 2-2.5% of diarrhea-hospitalized patients shed C. parvum oocysts. 10% of AIDS pateints have chronic cryptosporidiosis and this figure can be as high as 40% in certain developing countries. C. parvum is a diagnosed by either Ziehl-Neelsen stain or immunofluorescence in smears of unconcentrated specimens.