Giardiasis, more commonly known as beaver fever, is a common diarrheal illness in Canada and around the world. It is often caused by drinking untreated water, and less commonly through food and from person-to-person.
Giardiasis is an infection of the intestinal tract caused by the parasite Giardia lamblia. Giardiasis is common in the rural and wilderness areas of Western Canada, mostly spread through contaminated drinking water or by fecal-oral contact.
Although generally not a serious illness, it can have some long-lasting side effects if left untreated. This is an issue primarily for people whose immune systems are weakened. Giardiasis is easily prevented by treating water and handwashing.
Giardia may cause:
- diarrhea
- stomach cramps
- gas
- bloating
- frequent loose and pale greasy stools
- nausea
- poor absorption of fats and vitamins
- weight loss
- fatigue
Symptoms start an average of seven to ten days after exposure to the parasite and may last for months. Often a person can be infected and have no symptoms. In some cases, symptoms can return after you have started to get better. If you need advice, call 811 or see your primary care provider.
Giardiasis is commonly a water-borne disease. Giardia cysts (the dormant form of giardia) survive for long periods of time in the environment, including in cold water.
You can ingest giardia by:
- Drinking inadequately treated water contaminated by humans or animals leaving their droppings in or near water sources such as streams, rivers, lakes or shallow wells
- Ingesting contaminated water while swimming in lakes, ponds, streams, rivers, swimming pools and hot tubs
- Eating contaminated food
- Contact with the stool (poop) of an infected person (e.g., after diaper changing, or during sexual contact)
The spread of giardiasis in places like child care settings is a common cause of outbreaks when people infected with giardiasis are not able to follow recommended hygiene practices. Waterborne transmission plays an important role in localized outbreaks and is more common than transmission through food.
Untreated giardia can cause weight loss, excessive gas, and growth impairment, particularly in children. Following an infection, some people may experience ongoing diarrhea and cramps despite successful treatment, a condition known as post-infectious irritable bowel syndrome. Temporary lactose intolerance can occur.
Prolonged and/or severe infection can result in reactive arthritis. People who have weakened immune systems are more prone to long infections and should consult a health professional as soon as they suspect an infection. In rare cases, giardia can affect the liver, gallbladder, and pancreas.
Giardiasis is diagnosed with a stool test. If you think you have a giardia infection, see your doctor or primary care provider for testing, advice and treatment.
People with mild symptoms and healthy immune systems normally clear the infection in about a month. There are anti-parasitic medications that work well to treat giardiasis. Treatment is recommended if the giardia case has more severe symptoms, is immunocompromised, works/attends high risk settings (e.g., food handling or child care) or lives with an immunocompromised or pregnant person. Consult your doctor to determine if you need antimicrobial treatment.
Following infection, it is common to experience difficulty digesting milk and milk products. This causes symptoms similar to those of a giardia infection and can last several weeks. Avoid milk and milk products for a few weeks and then slowly add them back into your diet. Consult your doctor or primary care provider if you have questions.
If you recover without treatment, you may excrete giardia in your stools for several months and possibly infect others. Wash your hands thoroughly with liquid soap and water after using the toilet and before eating or preparing food.
If your local drinking water provider has issued a Boil Water Notice for your community water system, take the advice seriously.
Do not drink untreated surface water from springs, streams, rivers, lakes, ponds or shallow wells. Assume it is contaminated with animal waste. Boil or filter water from sources that are used for:
- drinking
- making ice cubes
- washing uncooked fruits and vegetables
- making baby formula
- brushing teeth
- rinsing dentures
- any purpose where water will be consumed without proper treatment
- Before eating
- Before handling food
- After using the toilet or changing diapers
- After touching animals
- Make sure children, particularly those who handle pets, wash their hands carefully before eating and on a regular basis if they suck their thumbs or put their hands in their mouths
- Wash your hands after sexual activity, especially if you have been in contact with fecal matter
People with diarrhea that could be caused by an infection should not go to work or school until their symptoms resolve. Giardiasis spreads easily in child care settings. If you are a food handler, health care worker, or work in or attend child care, it is possible for you to spread giardia to others in these settings.
Do not work while you have diarrhea or vomiting and do not return to work until 48 hours after your last loose stool or episode of vomiting. This time period will ensure you have a chance to recover and lower the possibility of spreading the infection to others.
Children in child care who have diarrhea can be cared for temporarily in an area separate from other children until picked up by their parents or guardians. Children should stay home until 48 hours after their last loose stool or episode of vomiting. To ensure proper hand washing, children in child care should be supervised by an adult when washing their hands.
- When camping, do not relieve yourself within 100 feet of a water source.
- If you have a giardia infection, do not swim in lakes, ponds, streams, rivers, swimming pools and hot tubs while you have diarrhea and until at least 48 hours after the diarrhea has stopped. Avoiding this activity will help to ensure that other swimmers do not become infected.
- Boiling: Bring water to a rolling boil for at least one minute and then allow it to cool. At elevations over 2,000 metres (6,562 feet) you should boil water for at least two minutes to disinfect. Boiling will not purify water that is obviously heavily polluted or chemically contaminated.
- Filtering: To effectively remove giardia cysts, filters must have an absolute pore size of 1 micron or be rated by the National Sanitation Foundation (NSF) for cyst removal. Cysts are 8 to 12 microns in length and will not pass through a filter pore of 1 micron. Some portable water treatment units used for camping meet the above requirements.
Jug-type water filters, such as Brita, are not effective in removing giardia. Some built-in water filtration systems will remove giardia, but they need regular and thorough maintenance to work effectively.
Other types of water treatment units, such as distillation units and combination (filtration and ultraviolet) units are also available. Check with local water purification suppliers or your local environmental health officer for more detailed information.
Giardia is moderately resistant to chlorine so treating water with chlorine is generally not effective in its removal. If you have no other options, you can attempt to disinfect water with unscented household bleach. Add two drops of bleach per litre (nine drops of bleach per imperial gallon) of untreated water. The treated water should be stirred and allowed to stand for at least 30 minutes prior to use. Double the amount of bleach if the water is cloudy.
