Our Health Library information does not replace the advice of a doctor. Please be advised that this information is made available to assist our patients to learn more about their health. Our providers may not see and/or treat all topics found herein.
What is giardiasis?
Giardiasis (say "jee-ar-DYE-uh-sus") is an infection of the intestines caused by the parasite Giardia lamblia.
The illness, also called giardia (say "jee-AR-dee-uh"), is most often a problem in undeveloped countries where tap water is not safe.
How can you become infected with giardia?
You may become infected with giardia if you eat food or drink water that is tainted with human or animal waste. In the United States and Canada, you can get giardia by drinking untreated water from wells, streams, rivers, and lakes. This is true even in mountain lakes and streams where the water may seem very pure. The infection can also happen if you swallow contaminated water while you swim.
You can get giardia from someone else through:
- Close contact with someone who is infected.
- Working in day care centers for young children. For example, if you change a diaper and don't wash your hands afterward, anything or anyone you touch could get infected. You could even get the illness yourself if you touch your mouth or eat food that you've touched. Children in day care centers are also more likely to get infected.
- Working or living in nursing homes or other care centers where people may have poor bowel control and poor hygiene.
- Some types of sexual contact, such as anal-oral contact.
What are the symptoms?
Giardia can cause diarrhea, stomach cramps, gas, and nausea. You may feel sick once and then get better. Or your symptoms may come and go for some time. Some children with giardiasis do not grow or gain weight normally. Sometimes giardiasis does not cause any symptoms.
After a person is exposed to the parasite, it usually takes 7 to 10 days for the infection to develop, but it can take from 3 to 25 days or longer. You can pass the infection to others during the entire time you are infected. You may be infected for months, even if you don't have symptoms.
How is it diagnosed?
Your doctor will ask questions about your past health and will do a physical exam to find out if you have giardiasis. He or she may also test your stool for the parasite that causes the infection.
How is it treated?
Your doctor may prescribe medicine to kill the parasite. Treatment also lowers the chance that you will pass giardia to others. It's important to take the medicine for as long as prescribed, so the infection does not come back.
In some situations, you may be tested for giardiasis even though you don't have any symptoms. For example, this could happen during an outbreak at a day care center.
If you have diarrhea, try eating small amounts of bland food until you feel better. This gives your bowel a rest. But you need to take frequent sips of clear fluids like rehydration drinks to avoid dehydration. This is especially important for children, because they can become dehydrated quickly.
Some people with giardiasis have temporary trouble digesting milk and milk products. This is called lactose intolerance. If you have this problem, avoid these foods for at least 1 month. Then slowly add them back into your daily meals as your body can handle them.
Can giardiasis be prevented?
There are some things you can do to avoid giardiasis.
- Don't drink untreated or unpurified water. If you are camping or hiking, boil or purify water from lakes and streams before you drink it.
- When you travel in high-risk areas, drink bottled water and avoid raw fruits and vegetables. Don't drink beverages containing ice cubes.
- Wash your hands often to prevent getting giardiasis from an infected person. This is very important not only after you change diapers, use the toilet, or help someone else use the toilet but also before you prepare food.
Other Works Consulted
- Adachi JA, et al. (2012). Infectious diarrhea from wilderness and foreign travel. In PS Auerbach, ed., Wilderness Medicine, 6th ed., pp. 1360–1374. Philadelphia: Mosby.
- American Academy of Pediatrics (2015). Giardia intestinalis (formerly giardia lamblia and giardia duodenalis) infections. In DW Kimberlin et al., eds., Red Book: 2015 Report of the Committee on Infectious Diseases, 30th ed., pp. 353–355. Elk Grove Village, IL: American Academy of Pediatrics.
- Huston CD (2010). Intestinal protozoa. In M Feldman et al., eds., Sleisenger and Fordtran's Gastrointestinal and Liver Disease, 9th ed., vol. 2, pp. 1905–1919. Philadelphia: Saunders.
- Roy SL, Hlavsa MC (2012). Giardiasis. In GW Brunette et al., eds., CDC Health Information for International Travel 2012: The Yellow Book. New York: Oxford University Press. Also available online: http://wwwnc.cdc.gov/travel/yellowbook/2012/chapter-3-infectious-diseases-related-to-travel/giardiasis.htm.
- Yoder JS, et al. (2010). Giardiasis surveillance—United States, 2006–2008. MMWR, 59(SS-6): 15–25.
Current as of: January 26, 2020
Author: Healthwise Staff
Medical Review: E. Gregory Thompson, MD - Internal Medicine
Adam Husney, MD - Family Medicine
W. David Colby IV, MSc, MD, FRCPC - Infectious Disease
To learn more about Healthwise, visit Healthwise.org.
© 1995-2020 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.