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What is giardia? Giardia (jar-deeya) is a parasite that enters the body through the mouth and lives in the small intestine of people and animals. Swallowing the parasite can cause symptoms like diarrhea in some people or no symptoms at all. An outer shell protects the parasite, which helps it to survive outside the body and in the environment for a long time. The shell also helps it resist chlorine disinfection. Giardia is found around the world, and is widespread in Canada.


  • Front of Giardia fact sheetGiardia Fact Sheet (PDF 77KB)
    View, download and print the Giardia Fact Sheet. Giardia (jar-deeya) is a parasite that enters the body through the mouth and lives in the small intestine of people and animals. Swallowing the parasite can cause symptoms like diarrhea in some people or no symptoms at all.

How do I get Giardia and how is it spread?

Giardia is passed through the bowel movement of a person or animal that has it in their intestines. Giardia can be found in soil, food, water or surfaces that have been contaminated with feces (poop) from infected animals or humans. Infection happens after swallowing the parasite.

Giardia can be spread:

  • By swallowing Giardia that was picked up by hands from surfaces (bathroom fixtures, changing tables, diaper pails or toys) contaminated with feces from an infected person;
  • By swallowing recreational water contaminated with Giardia (lakes, rivers, springs, ponds, streams, swimming pools or hot tubs can be contaminated with sewage or feces from humans or animals);
  • By eating uncooked food contaminated with Giardia;
  • Person to person through contact with infected feces, which can happen in child care centres or other settings where diapers or incontinence products are touched;
  • By touching animals or animal feces, including house pets, farm, and wild animals; and
  • Through sex activities that involve contact with another person’s feces.

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What are the symptoms of a Giardia infection?

Often, there are no symptoms with Giardia infection. A recent infection may cause diarrhea; loose, mucousy and pale, greasy stools; stomach cramps; bloating; upset stomach; severe gas; tiredness; weight loss; nausea and dehydration.

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How long after infection do symptoms appear?

Symptoms usually appear within 7 to 10 days, but can range from 3 to 25 days after a person becomes infected.

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How long do symptoms last?

In healthy people, symptoms of Giardia can last 2 to 6 weeks. Sometimes symptoms will last longer. Often symptoms will disappear on their own and in some cases medication is needed to treat the infection.

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Am I at risk for Giardia infection?

Everyone is at risk for getting Giardia. People most likely to become infected include:

  • Children who go to day care
  • Day care workers
  • People who care for someone sick with Giardia
  • International travelers
  • People who drink or swallow water from contaminated sources
  • Backpackers, hikers and campers who drink unfiltered, untreated water
  • Swimmers who swallow water while swimming in lakes, rivers, ponds and streams
  • People who drink water from shallow wells
  • People who are in contact with another person’s feces (poop) through sexual activity

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How do I prevent Giardia infection?

Proper Hand Washing

  • Make sure hands are properly washed with soap and water after using the toilet, changing diapers, helping others toilet, before eating and preparing food and after touching pets, farm or wild animals.
  • If working in a child or health care setting where diapers are changed, make sure hands are washed with soap and water after every diaper change even if gloves are used.
  • The six steps to good hand washing are:
    1. Wet hands with warm running water
    2. Put liquid soap on hands
    3. Lather hands and scrub for 20 seconds
    4. Rinse under running water
    5. Dry your hands with paper towels
    6. Use the towel to turn off the taps

 If you have diarrhea, stay out of swimming pools.

  • If you have diarrhea, stay out of swimming pools. Due to Giardia’s outer coat, it won’t be killed by the chlorine in the water.

Pasturized milk and milk products and safe drinking water

  • Always drink pasteurized milk and use only pasteurized milk products.
  • Always wash all vegetables and fruits with water from a safe supply. 
  • Do not drink water directly from lakes, rivers, springs, ponds or streams unless it has been filtered or chemically treated to remove Giardia. Use a filter that has an absolute pore size of at least 1 micron or smaller or one that has been NSF rated for “cyst removal.”
  • When travelling, camping or hiking, or if a “boil water” advisory has been issued, bring water to a full boil for one minute. This water can then be used for drinking, brushing teeth, rinsing dentures or contact lenses, making ice cubes, washing uncooked fruits and vegetables, and in recipes requiring water. Dishes should be washed with water that has been boiled.
  • When traveling in areas where water supply may be unsafe, avoid drinking tap water that has not been boiled or consuming drinks with ice made from an unknown water source. Eat only uncooked foods washed with boiled tap water.

Sexual Practices

  • Avoid sex practices that involve contact with stool.

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Date of creation: December 31, 2012
Last modified on: January 11, 2016


1Centers for Disease Control and Prevention. (2012). Giardia and Drinking Water from Private Wells Retrieved from
2Centers for Disease Control and Prevention. (2011). Parasites- Giardia Retrieved from
3Heymann, D. L. (Ed.). (2015). Control of communicable diseases manual (20th ed.). Washington, DC: American Public Health Association.