Cryptosporidiosis is a disease caused by ingesting or swallowing the intestinal parasite Cryptosporidium parvum. Watery diarrhea and abdominal cramping are the most common major symptoms, while other symptoms may include nausea, vomiting, fatigue, weight loss and low-grade fever. Symptoms may last as long as 30 days in otherwise healthy individuals, but in persons with weakened immune systems symptoms can persist indefinitely and possibly lead to serious illness and death. The parasite Cryptosporidium parvum is found in the feces of infected animals and people. Inadequate disposal of feces and water run-off from animal habitats may also contaminate drinking water supplies and natural-resourcesal water sites.