Cryptosporidium is a protozoan parasite that causes an infection called cryptosporidiosis. It is most commonly found in children aged between 1 and 5 years, but it can affect any age group. Infection may be asymptomatic. Symptoms of cryptosporidiosis may include Diarrhea Abdominal pain, Nausea and vomiting Fever Respiratory problems prolonging from several days to more than a month. The examination of multiple faecal specimens may be required to detect cryptosporidium.