Giardiasis Patient Information Fact Sheet

What is giardiasis?
Giardiasis is a diarrheal disease caused by the parasite Giardia that can affect the small intestine. The most common symptom is loose, pale and greasy stools, especially in the morning. Other symptoms include abdominal cramps, bloating, and foul smelling flatulence. If not treated, the illness can persist for a number of months leading to malabsorption of nutrients and weight loss.

How do you contract giardiasis?
The giardiasis cysts are passed from person to person via contaminated food and water. Outbreaks have also been associated with recreational water that has been contaminated with human or animal feces. Giardiasis occurs throughout the world but is most prevalent in areas with poor sanitation.

The incubation period can be anywhere between 2–6 weeks. The giardiasis cysts can be transmitted to others until the infection has been successfully treated.

How is giardiasis diagnosed?
Diagnosis is usually confirmed by identifying the cysts in a sample of feces.

How is giardiasis treated and prevented?
Metronidazole (Flagyl), an antibiotic, or antiparasitics such as nitazoxanide (Alinia) and tinidazole (Tindamax), are usually prescribed. Relapses may occur and the treatment may need to be repeated.

Take care with food and water hygiene. Boil or purify drinking water. The cysts are very resilient and not always destroyed by chemical treatments alone. To treat water effectively, use a filter before chemical treatment (iodine is best) or use an iodine resin purifier. Avoid swimming and bathing in water unless known to be safe.

Further information
For more information visit www.cdc.gov/parasites/giardia/gen_info/faqs.html

Last Reviewed: May 2013