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Diseases & Topics


Giardia is a microscopic parasite that causes a diarrheal illness called giardiasis. A parasite is an organism that feeds off another to survive. Giardia is found on surfaces or in soil, food or water that has been contaminated with feces from infected humans or animals.

Once a person or animal (for example, cats, dogs, cattle, deer or beavers) has been infected with Giardia, the parasite lives in the intestines and is passed in the feces.

Once outside the body, Giardia can sometimes survive for weeks or months, since it is protected by an outer shell that also makes it tolerant to chlorine disinfection. While the parasite can be spread in different ways, water (drinking water and recreational water) is the most common method of transmission.

Giardiasis can be treated with prescription medicines. People with diarrhea from Giardia infection, particularly infants and pregnant women, should also drink plenty of fluids to avoid dangerous dehydration.

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