Morphology: A protozoan parasite (oocyst) that is protected by an outer shell that allows it to survive outside the body for long periods and makes it resistant to chlorine.
Habitat: Can live in the intestines of humans and wild animals in every region of the USA and throughout the world. Can get into municipal drinking water and recreational water (swimming pools and water slides) with malfunction of sewage systems, with flooding and storm water run-off and agricultural run-off.
Disease or illness: Mild fever, stomach cramps and watery diarrhea 4-7 days after exposure. The illness can last 1-3 weeks; Can be deadly to immune-suppressed or older people.
Who is at risk: Children and those with a weak immune system are at greatest risk.
Avoidance techniques: Effective treatment of municipal water supply including UV light, ozone, and filtration in addition to chlorine. Check well-water periodically especially after local flooding. Boil contaminated water for 1 minute or 3 minutes at higher altitudes.