Causes and Symptoms of Giardiasis

Giardiasis is a diarrheal illness caused by Giardia intestinalis (also known as Giardia lamblia), a one-celled, microscopic protozoan parasite

The parasite is passed in the stool of an infected person or animal. The parasite is protected by an outer shell that allows it to survive outside the body and in the environment for long periods of time.

During the past 2 decades, Giardia has become recognized as one of the most common causes of waterborne disease (drinking and recreational) in humans in the United States. Approximately 970 to 1550 cases of giardiasis are reported to the Minnesota Department of Health each year.

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Fact Sheets
Duration of Illness

Fact Sheet


Symptoms include:

  • watery diarrhea
  • vomiting
  • stomach cramps
  • loss of appetite
  • weight loss
  • and a slight fever.

Some people have no symptoms.

Symptoms generally begin 1-2 weeks after infection.

Duration of Illness

  • Symptoms last about 2-6 weeks in healthy persons.


Giardia lives in the intestine of infected humans or animals. Millions of germs can be released in a bowel movement from an infected human or animal. You can become infected after accidentally ingesting the parasite.

Giardia may be found in soil, food, water, or surfaces that have been contaminated with the feces from infected humans or animals.



Do you suspect that you have a foodborne illness? Visit reporting suspected foodborne illnesses.


Updated Tuesday, 16-Nov-2010 12:21:12 CST