Giardiasis is an infection of the intestine caused by a parasite called Giardia lamblia (also known as Giardia intestinalis and Giardia duodenalis). “Beaver fever” is a common name for giardiasis, though other domestic and wild animals can carry Giardia as well. People or animals who have a Giardia infection—whether showing signs of illness or not—can pass the parasite in their feces (stool), which may contaminate water, soil or food. The parasite can live for many weeks or months in the environment because it is protected by a strong coating or shell. Giardia are a common cause of diarrhea and affect children and adults worldwide.

How is giardiasis spread?

People may become ill with giardiasis by:

  • swallowing contaminated water when swimming or playing in recreational water such as lakes or rivers, and less commonly in swimming pools, splash pads, and water parks
  • drinking water from an unknown or an inadequately treated source
  • eating food that has been contaminated with feces or handled by someone who has a Giardia infection who did not properly wash hands after using the toilet and before preparing food
  • getting feces from an infected pet or animal on one’s hands and then into one’s mouth
  • touching surfaces (such as bathroom handles, changing tables, toys, or diaper pails) that have been soiled with feces from an ill person, not washing one’s hands, and then touching one’s mouth
  • oral-fecal contact during sex with someone who has a Giardia infection
What are the symptoms of giardiasis?

Symptoms of giardiasis usually appear between 7 to 10 days after coming in contact with the parasite but it may take as little as 3 days or 25 days or longer to show symptoms. Some people may have Giardia parasites in their feces without having any symptoms. Symptoms may include abdominal cramps and bloating, gas, frequent loose, pale, greasy stools, bad smelling diarrhea, nausea, vomiting, low grade fever, fatigue and weight loss.

What is the treatment for giardiasis?

Most healthy people with giardiasis will recover without complications. Your health care provider may prescribe antibiotic medications to treat giardiasis. People who have weakened immune systems are at risk for more severe symptoms and disease. If symptoms are persistent or severe, it is important to see a healthcare provider.

Are there any restrictions or special considerations for people ill with giardiasis?

Those ill with giardiasis should stay at home while they are having symptoms. People whose work involves preparing or handling food, people who provide childcare or healthcare, and children who attend daycare should remain at home until the diarrhea has stopped for at least 24 hours; this includes if you have been prescribed antibiotics. If you have taken anti-diarrheal medication, you must be symptom-free for 48 hours after stopping the anti-diarrheal medication before returning to the work or places mentioned above. Children who still use diapers or may have accidental incontinence of stool must not to use recreational water, such as swimming pools and splash pads for 1 week after symptoms resolve.

How can I protect myself against giardiasis?

To prevent becoming ill with giardiasis:

  • Avoid swallowing water while swimming; do not drink untreated water from lakes, streams and rivers.
  • Avoid local water when travelling to countries where the water supply is uncertain; instead use only sealed bottled water or treated (chemically disinfected or boiled) water for drinking, brushing teeth, preparing foods, making ice, and cooking.
  • Beware of raw foods washed in local water when travelling; eat only cooked food and fruit that can be peeled after it has been washed with water from a safe source.
  • Wash your hands well with soap and water for at least 15 seconds before preparing food, before eating, after using the toilet, after changing diapers, after handling pets or their feces, and anytime hands may be dirty.
  • Avoid preparing foods or drinks for others if you have diarrhea.
  • Wait to resume sexual activity until you no longer have diarrhea. You may continue to have Giardia parasites in your stool after you recover, so wash your body (genitals, anus, and hands especially) before and after sexual activity.
What is Ottawa Public Health’s role?

Labs and health care providers must report all cases of giardiasis to public health. OPH investigates all cases to find a source of illness and provide education. OPH will investigate further if we find a common source of illness. 

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