688 Modern Food Microbiology (from vertebrate animals to humans) is most likely where infected animals (such as calves) deposit fecal matter to which humans are exposed The disease may be contracted by drinking untreated water Oocysts at levels of 2–112 per liter were found in 11 samples of water from four rivers in Washington and California.74 Although the minimum infectious dose for humans is not known, two of two primates became infected after the ingestion of 10 oocysts.2 The organism has been shown to be an etiological agent of travelers’ diarrhea.102 Symptoms, Diagnosis, and Treatment The clinical course of cryptosporidiosis in humans depends on the immune state, with the most severe cases occurring in the immunocompromised In immunocompetent individuals, the organism primarily parasitizes the intestinal epithelium and causes diarrhea The disease is self-limiting, with an incubation period of 6–14 days, and symptoms typically last 9–23 days In the immunocompromised, diarrhea is profuse and watery, with as many as 71 stools per day and up to 17 l per day reported.32 Diarrhea is sometimes accompanied by mucus but rarely blood Abdominal pain, nausea, vomiting and low-grade (