Causes of Giardia infection (giardiasis)

Learn about the causes of Giardia infection, how it’s spread and where it’s found.  

On this page

• Cause of Giardia infection
• How Giardia infection is spread
• Where Giardia infection is found

Cause of Giardia infection

Giardia infection is caused by microscopic parasites, called Giardia, that are found in water. These parasites cause an intestinal illness called giardiasis, which is sometimes called ‘beaver fever.’

How Giardia infection is spread

Giardia can be spread by:  

• touching contaminated surfaces
• drinking untreated water from rivers or lakes
• eating or drinking contaminated food or water
• exposure to the feces of infected animals, such as pets and livestock
• exposure to infected human feces (for example, during sexual contact)

People and animals become sick if they swallow the parasite. The parasite is then passed in the feces of the infected human or animal. 

How food and water become contaminated

Food can become contaminated with Giardia if it comes into contact with:

• contaminated water
• feces from infected humans or animals, such as pets and livestock

Water sources can become contaminated with Giardia if:

• feces from infected humans or animals enter the water
• they are not treated adequately

Where Giardia infection is found

Giardia parasites are commonly found in or on:

• contaminated food and water
• untreated water from rivers and lakes
• contaminated surfaces, such as change tables and bathroom handles 
• intestines and feces of infected humans or animals, such as pets and livestock

The parasite can withstand harsh environmental conditions and can survive for weeks or months.