by Rick Alan
Giardiasis is a gastrointestinal infection. It is one of the most common parasitic diseases in the world.
Giardiasis is caused by a tiny parasite called Giardia lamblia. Giardia cysts are a resistant form of the parasite that can survive outside a human or animal body. These cysts cause the spread of this disease. For infection to occur, a person must ingest Giardia cysts by mouth. After cysts are ingested, the parasites start growing and multiplying in the small intestine. Ingesting as few as ten parasitic cysts can cause an infection.
Giardiasis can occur by:
Factors that increase your risk of getting this disease include:
Symptoms usually start 5 to 28 days after infection. Not all people who are infected have symptoms. But, all people who are infected can transmit the disease.
Symptoms may include:
The doctor will ask about your symptoms and medical history. A physical exam will be done.
Your doctor may want to lab results from your bodily fluids, waste products, or tissue. This can be done with:
If you are diagnosed with giardiasis, everyone living in your household should be tested for infection as well.
Giardiasis is treated with a prescription antiparasitic drug. The medication is usually given for 5 to 10 days. Some of these medications include:
This condition may be resistant to any of these medications or to several others that are sometimes used. This may make treatment difficult. It may also mean that you may be sick longer.
Follow these guidelines to prevent getting or spreading giardiasis:
American Academy of Family Physicians
National Institute of Allergy and Infectious Diseases
The Canadian Association of Gastroenterology (CAG)
Public Health Agency of Canada
Adam RD. Biology of Giardia lamblia . Clin Microbiol Rev. 2001;14:447
Giardiasis. KidsHealth.org website. Available at: http://kidshealth.org/parent/infections/stomach/giardiasis.html . Updated September 2011. Accessed January 8, 2013.
Parasites–giardia. Centers for Disease Control and Prevention website. Available at: http://www.cdc.gov/parasites/giardia/ . Updated March 8, 2011. Accessed January 8, 2013.
Nash TE. Surface antigenic variation in Giardia lamblia . Mol Microbiol. 2002;45:585.
Last reviewed November 2012 by Michael Woods, MD