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Fact Sheet: Giardiasis

What is giardiasis?

Giardiasis is an illness caused by Giardia lamblia, a one-celled parasite that can only be seen under a microscope. It lives in the guts of people and animals. During the past 15 years, Giardia lamblia has become recognized as one of the most common causes of waterborne disease in humans in the United States. This parasite is found in every region of the United States and throughout the world.

How is Giardia lamblia spread?

The parasites are spread by what is called fecal-oral transmission, which putting something in your mouth that has come in contact with the bowel movement of a person with giardiasis. This happens by swallowing polluted water, eating uncooked contaminated food or by touching and putting contaminated objects in the mouth.

Giardia can form though cysts that:
  • usually do not die in chlorine-treated water
  • continue to pass in the bowel movements of infected persons for many weeks after symptoms have stopped.

What are the symptoms of giardiasis?

Diarrhea (frequent and watery bowel movements), stomach cramps, and nausea (feeling the need to throw up) are the most common symptoms of giardiasis. These symptoms may lead to weight loss and dehydration (loss of liquids). However, not everyone infected has symptoms.

Who is at risk?

Persons at increased risk for giardiasis include diaper-aged children who attend day care centers; childcare workers; international travelers; hikers; campers; and others who drink untreated water from contaminated sources. Some persons who drink city or town water may also be at risk. Several community-wide outbreaks of giardiasis have been linked to drinking city or town water contaminated with Giardia.

How is giardiasis diagnosed?

Giardiasis is diagnosed by testing a sample of feces to see if you are infected. Because Giardia can be hard to find, you may be asked for many test samples over several days.

What is the treatment for giardiasis?

Several prescription drugs are available to treat Giardia. When children are treated, they usually get different medicine than adults.

How can I prevent giardiasis?

  • Wash your hands with soap and water after using the toilet and before handling or eating food.
  • Wash your hands thoroughly with plenty of soap and warm water after every diaper change, even when gloves are worn.
  • Avoid water or food that may be polluted.
  • Wash and peel all raw vegetables and fruits before eating.
  • Avoid drinking water from lakes, rivers, springs, ponds, or streams.
  • Avoid drinking water that may be contaminated.
  • During community-wide outbreaks caused by contaminated drinking water, boil drinking water to kill the parasite and make the water safe to drink.
  • When traveling in countries where the water supply may be unsafe, avoid drinking unboiled tap water and avoid uncooked foods washed with unboiled tap water. Bottled or canned carbonated beverages (pops, seltzers), or pasteurized fruit drinks, and steaming hot coffee and tea are safe to drink. Check the label on bottled water to make sure it has been properly filtered before drinking.

My water comes from a well; should I have my well water tested?

Well water should be tested if you answer yes to the following questions:
  • Are other users of your well water ill with giardiasis? If yes, your well may be the source of infection.
  • Is your well located at the bottom of a hill or is it considered shallow? If so, runoff from rain or flood water may be draining directly into your well, causing contamination.
  • Is your well in a rural area where animals graze? Animals can contaminate well water if the waste gets into the ground water. This can occur if your well has cracked casings, is poorly constructed or is too shallow.
If you answered yes to any of the above questions, then your well water should be tested. Tests that target Giardia are expensive, difficult, and usually require hundreds of gallons of water to be pumped through a filter. You may want to think about doing a well test for fecal coliforms. This test costs less and will tell if any animal or human waste is in your water. If the water is polluted with waste, it is likely that it is polluted with Giardia and other harmful bacteria and viruses. Many local telephone books have listings of where to call to get your water tested and treated.

My child was recently diagnosed with giardiasis, but does not have any diarrhea. My health care provider says treatment is not necessary. Is this true?

The American Academy of Pediatrics says that treatment is generally not necessary. However, there are a few exceptions. If your child does not have diarrhea, but is having nausea, is tired a lot, is losing weight, is not hungry or not eating, treatment should be looked into. If your child attends a day care center where an outbreak continues to occur despite efforts to control it, screening and treatment all children is a good idea. The same is true if several family members are ill, or if a family member is pregnant and therefore not able to take the most effective anti-Giardia  medications.

If you think you may have giardiasis, contact your doctor or health clinic for information on where you can get tested. If you can't afford a doctor and/or are not currently on a health plan or insurance, call 1-800-SAFENET (723-3638) for information on low-cost clinics near you.

Issued by: The Oregon Health Division
Date: December, 1999, revised January 2001

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