An illustration of diseases caused by water borne protist parasites along with brief description:

1. Entameoba stuck in the walls of intestine. Entameoba causes diseases known as amebic dysentry. The amoebas live in the intestines, where they absorb food from the host. They also attack the wall of the intestine itself, shown above, destroying parts of it and causing severe bleeding.
2. Cyptosporidium is resistant to the chlorine compounds often used to sanitize drinking water and therefore poses a special threat to public water systems. In 2008, an outbreak in Utah sickened more than 2000 people.
3. Giardia, a flagellated protist. The flagellated protist Giardia causes sevre diarrhea and digestive-system problems. Even crystal-clear streams may be contaminated with Giardia, which produces tough cysts that can be killed only by boiling water thoroughly or by adding iodine to the water.