Michigan Environmental Education Curriculum
Water Quality - Pollutant Sources and Impacts

Giardia lamblia cyst

Giardia lamblia cyst

Protozoa are microorganisms with several animal-like characteristics: they can eat other organisms (like bacteria) and they can move around. The protozoan life cycle often alternates between an active stage (which causes damage to the human body) and an encysted stage (which is the form that is passed along and causes infection). Cysts are resistant to the acids present in the digestive systems of animals and thus pass out of the body with fecal material. Protozoan diseases often lead to diarrhea and cramps. In the case of amoebic dysentery, the protozoans can destroy internal tissues, where bleeding accompanies diarrhea.

Examples of the waterborne diseases caused by bacteria are:

  • amoebic dysentery – 34,000 deaths worldwide each year
  • giardiasis
  • cryptosporidiosis

Medicines are available to treat persons suffering from these diseases. Protozoan cysts are difficult to destroy, even by the normal methods used to eliminate pathogens from drinking water. Backpackers are encouraged to boil their drinking water. Protozoan pathogens are removed from public drinking water supplies by filtration.


Beaver Fever

Crypto in Milwaukee

Cryptosporidium parvum oocysts

Cryptosporidium parvum oocysts

Start > Title > Site Map > Credits > Glossary > Help
Michigan Tech > Tech Alive > Series Index > Michigan Environmental Education Curriculum > Module Index > Water