by Rick Alan
Giardiasis is a common intestinal infection that is found around the world.
A specific parasite cause the infection. Giardia cysts are a form of the parasite that survive outside of humans and animals. The cysts spread the infection. You can get it by swallowing the cysts. It grows once it gets to the small intestine. It can pass to you from water, food, or stool that have the cysts. Examples include:
Giardiasis spreads easily. It takes only 10 cysts to cause infection.
Risk Factors TOP
Giardiasis is more common in places without proper water or sewage treatment. Places in Asia or South America have the highest infection rates.
Risk is also higher if you:
Most people don’t have symptoms. If they do appear, they may cause:
If you don’t have symptoms, you can still pass the infection to others.
The doctor will ask about your symptoms. You will be asked about your health and travel history. Your answers and a physical exam may point to giardiasis. If needed, you may also have:
If you have the infection, others in your household will need testing.
Medicines will treat the infection. Sometimes, the parasite is resistant. This can make you sick longer.
To lower your chances of giardiasis:
Wash your hands often, mainly:
When traveling overseas:
Centers for Disease Control and Prevention
IDSA—Infectious Diseases Society of America
Canadian Public Health Association
Giardiasis. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T113949/Giardiasis. Updated August 7, 2017. Accessed May 29, 2018.
Giardiasis. Kids Health—Nemours Foundation website. Available at:
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Updated August 2017. Accessed May 29, 2018.
Giardiasis. Merck Manual Professional Version website. Available at: https://www.merckmanuals.com/professional/infectious-diseases/intestinal-protozoa-and-microsporidia/giardiasis. Updated February 2017. Accessed May 29, 2018.
Parasites–giardia. Centers for Disease Control and Prevention website. Available at: https://www.cdc.gov/parasites/giardia. Updated July 22, 2015. Accessed May 29, 2018
Last reviewed May 2018 by David L. Horn, MD, FACP
Last Updated: 5/29/2018
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