Giardia and Cryptosporidium are widespread intestinal parasites that cause diarrheal illnesses in people. They are not bacteria or viruses, but protozoa with complex life cycles, which exist in a cyst form, very much like a microscopic egg. Giardia cysts are extremely small; they are 10 times smaller than the smallest object that can be seen with the naked eye, and Cryptospordium oocysts are even smaller. See more information on cysts below.
What health problems are caused by Cysts (Cryptosporidium and Giardia)?
When even a few cysts are consumed, they enter the small intestine, where they excyst, or "hatch," and can multiply into millions of protozoa. Giardiasis and cryptosporidiosis are flu-like illnesses with symptoms involving persistent diarrhea, nausea, abdominal cramps, weight loss and sometimes dehydration.
How do we get Cysts (Cryptosporidium and Giardia)?
Cysts and oocysts are commonly transmitted from the environment to humans through inadequately or improperly treated drinking water. Most surface water sources either contain or are vulnerable to Giardia cyst and Cryptosporidium oocyst contamination at one time or another. Since some people are carriers, cysts and oocysts may enter the water through treated and untreated sewage discharges. Of particular concern are those animals that live in or near the water, since they are likely to deposit cysts and oocysts directly into drinking water supplies. Livestock are notorious carriers of Cryptosporidium, while beavers have been identified as a carrier of Giardia. Once in the water, both protozoan cysts remain capable of infecting a host for many months, especially in colder water where they are more resistant to natural die-off. Since many animals are carriers of cysts and oocysts, you should never drink untreated water from even the clearest looking stream or river. Giardia has became famous as the "backpacker's disease" because so many unsuspecting hikers and backpackers often became ill after drinking water directly from clear, mountain streams. You should also avoid untreated spring water--no matter how clean it looks--because cysts, oocysts, bacteria and viruses may contaminate the spring supply at any time.
The recommended method of treatment is a Reverse Osmosis System or other point-of-use water filter capable of removing particles less than one micron in diameter.