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Water and Waste Department

Water treatment program

The facts about Cryptosporidium and Winnipeg's water supply

Cryptosporidium (crip-toe-spor-ID-ee-um) is a parasite that may contaminate water supplies and cause human illness. The Winnipeg Regional Health Authority and the City of Winnipeg want you to know about this disease-causing organism and Winnipeg's drinking water.

What is Cryptosporidium?

Cryptosporidium (Crypto) is a microscopic, disease-causing parasite. It may be present in the bowel movements (feces) of infected animals and people. It is spread when feces contaminate water or, less commonly, food that people eat or drink. Contaminated animal droppings from livestock, wild animals or pets may wash into rivers, creeks or lakes.

Is concern about Crypto unique to Winnipeg?

No. Crypto is a concern to all public water utilities that rely on surface water supplies for drinking water.

How do people get infected?

There are many potential pathways to infection. People may be infected by drinking contaminated water or eating raw or undercooked food contaminated with Crypto. As well, people may be infected by coming into contact with the feces of infected individuals or animals, or surfaces contaminated with fecal matter.

Is Winnipeg's water supply tested for Cryptosporidium?

Yes. Since 1994, the City has regularly tested the water supply for Crypto at Shoal Lake and at the Deacon Reservoir outlet. Water samples taken from Shoal Lake and Deacon Reservoir are normally negative for Crypto.

We get our water from Shoal Lake, on the border between Manitoba and Ontario. Water flows from Shoal Lake to Winnipeg by gravity through a 135 kilometre long aqueduct (concrete pipe). The water is stored in Deacon Reservoir, a large reservoir that holds 8.8 billion litres, enough water to supply Winnipeg for about 20 days. Water passes from Deacon Reservoir to three smaller reservoirs and pumping stations in different areas of the city. From these, it is delivered to water users throughout the city.

What is the City doing to prevent contamination of the water supply?

The best means of preventing a possible waterborne outbreak of Crypto is to protect the watershed from contamination. The Shoal Lake watershed has few sources of potential Crypto contamination, with low human activity, few farm animals, and no livestock feed lots.

We work with the First Nation communities in the Shoal Lake area, the federal government, and the provincial governments of Manitoba and Ontario to make sure that development in the area does not affect water quality.

Does the City of Winnipeg treat its water for Cryptosporidium?

Yes. Ultraviolet light disinfection is in place and protecting Winnipeg residents against waterborne parasites as part of the water treatment program. Our new water treatment plant houses the remaining treatment processes.

Water treatment will reduce the already low risk of a waterborne outbreak of Crypto. However, even a well-operated water treatment system cannot ensure that drinking water will be completely free of this parasite.

Can Crypto make people ill?

Yes. Crypto can cause a diarrheal illness called cryptosporidiosis. However, not every person who becomes infected with Crypto feels ill or notices symptoms.

Who is at risk from Cryptosporidium?

Anyone can get it. For people in good health, the illness may come and go for up to a month and usually ends on its own. The disease can cause prolonged distress and be life-threatening for people with extremely weak immune systems. This includes:

  • people with HIV/AIDS
  • people with cancer
  • transplant and other patients taking immunosuppressive drugs
  • people with genetically weakened immune systems
What are the symptoms of cryptosporidiosis?

Symptoms often start 2 - 10 days after exposure and may last up to 30 days in individuals with healthy immune systems. Symptoms of cryptosporidiosis can include diarrhea, abdominal cramps, headaches, loss of appetite, nausea and a mild fever. These symptoms may lead to dehydration. A safe and effective treatment for cryptosporidiosis has not been developed.

How can I protect myself from Crypto?

You can take the following measures to reduce the risk of acquiring Crypto:

  • Wash your hands often with soap and water, especially before eating, before and after preparing food, and after gardening, using the toilet, changing diapers or handling animals.
  • Don't drink untreated water directly from rivers, creeks, streams, springs, or lakes.
  • Avoid swallowing water when swimming in pools, water parks and natural bodies of water such as lakes and rivers.
  • Use only pasteurized milk, dairy products, drinks and juices.
  • Practice safer sex (avoid fecal contact).
What additional steps can severely immune compromised individuals take to protect against Crypto?

People with severely weak immune systems who have been advised to take the precaution of boiling water should heat water to a rolling boil for one minute. Boiling is the best way to ensure that water is free of Crypto. After the boiled water cools, place it in a clean bottle or pitcher with a lid and store in the refrigerator. Use this water for:

  • drinking
  • making ice
  • making hot coffee, tea or chocolate
  • making iced tea or iced coffee
  • making fruit drinks that require water to be mixed with frozen concentrate

Another tip is to consider choosing canned or bottled soda, seltzer, and fruit drinks rather than fountain drinks, as fountain drinks are usually made with tap water that hasn't been boiled.

Should everyone boil their water?

The risk of contracting cryptosporidiosis from Winnipeg's water remains very low. Nor is cryptosporidiosis usually a serious illness for the general population. Therefore, we do not recommend that the general public boil their drinking water.

Is bottled water safe from Cryptosporidium?

Parasites such as Crypto can live for weeks in water, including bottled water, even if the water is refrigerated. If you are buying bottled water, read the labels carefully.

Not all bottled water may have been processed by a method effective against Crypto. Water labelled as follows has been processed by a method effective against Crypto:

  • reverse osmosis treated
  • distilled
  • filtered through an absolute 1-micron filter or smaller filter
  • 1 micron absolute
  • ozonation

For information on bottled water, visit Health Canada. If you have any questions about a specific bottled water product, call the Canadian Food Inspection Agency at 204-983-2220.

Do water treatment devices protect against Cryptosporidium?

Some point-of-use treatment devices can be effective against Crypto. The following devices are designed to remove Cryptosporidium:

  • reverse osmosis device
  • filter with absolute pore size of 1 micron or smaller
  • devices with this certification on their label: ANSI/NSF Standard 53 for cyst removal

Water filters may not be as effective against Crypto as boiling water because some filters may have manufacturing flaws that allow small numbers of Crypto to get past the filter. Also, poor maintenance or failure to replace filter cartridges as recommended by the manufacturer can cause a filter to fail.

Filters may collect disease-causing organisms from water, so you should thoroughly wash your hands before and after changing the filter. A person with a severely weak immune system should not change the water filter.

For information on home water treatment devices, you can call the NSF International free hotline at 1-877-867-3435 or visit:

If you want to buy a water treatment device, Health Canada strongly recommends that you buy one that is certified by ANSI/NSF.

Where can I get more information on Crypto and my health?

For information on Crypto and your health, call Health Links-Info Santé at 204-788-8200.

Where can I get more information on Winnipeg's water?

Check out our water quality information or contact us.

Where can I get more information on Crypto?

Additional information is available from:

This fact sheet is for information only and is not meant to be used for self-diagnosis or as a substitute for consultation with a health care provider. If you have any questions about cryptosporidiosis or think that you may have a parasitic infection, consult a health care provider.

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Last updated: August 7, 2018

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