Question: My husband and I are taking our children (7 and 10 years) camping in the High Sierras this summer. I must have been warned by three different people about Giardia and the water. What is Giardia, and are there any precautions I need to know about?
Answer: Giardiasis refers to an infection caused by the parasite Giardia lamblia. Giardia is the most common parasite found in the United States, and it is found worldwide. It is usually acquired by drinking water that is infested with the Giardia cysts. When this happens, the cysts make their way to the upper portion of the intestinal tract just beyond the stomach. That is where they "take up residence" and mature into the adult form. The adult Giardia excrete cysts which are passed in the stool of the host. Humans are the principal reservoir of Giardia, however, dogs, cats and other animals can become infected and sustain the life cycle. It is the passing of the cysts in the feces that contaminates the streams and lakes.
The symptoms of Giardia are variable. Some people are infected, yet have no symptoms at all. They do shed the cysts in their stools, and as such, are considered "carriers". Some people have a sudden onset of severe abdominal pain and diarrhea--much like a viral intestinal infection. Less fortunate individuals have a prolonged, or protracted course marked by intermittent flare-ups of intense gas, bloating, abdominal pain, fatigue, weight loss and loss of appetite.
The incubation period is from 1-4 weeks, and an infected person can shed the cysts in the stools for up to months. Many, if not most, of the streams and lakes in the United States are infested with Giardia. Campers and hikers must exercise extreme caution when using this water as a drinking source. Check with the Forest Service about the specific area where you will be camping.
There are methods available to make this water safe to drink. By far the most effective and safe way is to hard boil the water for 5 minutes. This is what is recommended by the Center for Disease Control.
There are also iodine tablets that can be used to treat the water. These will kill the cysts, although, the killed cysts are not removed and the water is left with an "iodine after taste". Chlorine tablets will not kill the cysts.
There are also portable filtration systems available that will remove the Giardia cysts as well as many bacteria. The price of these systems range from $25-$200. They are portable, but must be carried along.
Should someone contract Giardia, it is a treatable disease. There are a number of anti-parasite drugs that are effective in eradicating the disease. Some of these are over 95% effective provided the infected person completes a full course of therapy.
Hopefully this answers your question, and happy camping.