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Water Talk - Enteric protozoa (Giardia and Cryptosporidium) in drinking water

Health Canada has updated the guideline for enteric protozoa in drinking water to protect the health of Canadians. Learn about the health effects of Giardia and Cryptosporidium and how to reduce your exposure from your drinking water.

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Enteric protozoa in drinking water

Enteric protozoa are tiny parasites that can infect the gut of humans and other mammals and cause illness. Giardia and Cryptosporidium are two types of parasites in the enteric protozoa family.

They can be present in:

Surface water (e.g. rivers and lakes) can become contaminated when feces containing the parasites are flushed into the water. If you have a well, it needs to be carefully monitored to make sure it is not at risk of contamination from feces. 

Enteric protozoa can be spread in several ways (such as from person-to-person or food), but water is one of the most common.

Health effects of enteric protozoa in drinking water

If there is even just a few enteric protozoa in your drinking water, you can get sick. If you are generally healthy, the illness should not be severe. If you have a compromised immune system, for example if you have AIDS or cancer, or if you’ve had a transplant and are receiving immunosuppressive drugs, the illness can be life threatening.

Enteric protozoa may cause immediate and long-term health effects. Giardia causes an intestinal illness called giardiasis, sometimes referred to as “beaver fever”. Cryptosporidium causes a similar illness called cryptosporidiosis. In both cases, the symptoms may include:

Persons, especially children, may suffer from recurring symptoms, which may persist for months or years.

If you have diarrhea and think that it is because of Giardia or Cryptosporidium, you should consult your healthcare provider and mention that you may have been in contact with water or food that could be contaminated.

Guideline for enteric protozoa in drinking water in Canada

To ensure the safety of drinking water, Health Canada worked with provinces, territories and other federal departments to establish a health-based treatment goal for enteric protozoa in drinking water.

If there is a risk of enteric protozoa being present in sources of water, it should be treated to filter or disinfect at least 99.9% of the Giardia and Cryptosporidium. Most surface water sources across Canada have some Giardia and Cryptosporidium in them. Groundwater sources should be carefully assessed to determine whether the supply is at risk of contamination by enteric protozoa.

How to reduce your exposure to enteric protozoa in drinking water

If there is reason to believe that Giardia or Cryptosporidium is in a public drinking water supply an advisory will be put out to the community to boil the water before drinking it. In the case of a disease outbreak, municipal, provincial or territorial authorities will provide more information.

If you have a private well, laboratory tests are not recommended because testing to detect Giardia or Cryptosporidium is difficult and expensive. Instead, you should make sure feces do not get into your well water. More information about protecting your well water from contaminants that can make you sick can be found here. Treatment of the water from your well is a good option to reduce your exposure.

If your water is contaminated by feces, you should boil all the water you use for:

You don’t need to boil your tap water when you use it for other household purposes, such as bathing, showering, laundry, or washing dishes. Infants, toddlers and people with compromised immune systems should be sponge bathed to reduce the chance of swallowing contaminated water.

If you are pregnant or breastfeeding

If you are pregnant or breastfeeding and suspect that your drinking water may contain feces, these same actions will protect your health; you are not at higher risk of becoming ill.

Removing enteric protozoa from drinking water

Provinces and territories regulate municipal drinking water supplies. Consumers don’t need any additional treatment for Giardia and Cryptosporidium for drinking water supplied by a municipality.

Using water treatment devices

If your drinking water comes from a well, treatment options for Giardia and Cryptosporidium include:

Filters you use should meet one of the following NSF/ANSI Standards:

UV disinfection treatment units you use should meet NSF/ANSI Standard 55 Class A.

UV disinfection is intended for water that is usually clear (that is, not coloured, cloudy or turbid). If the water is cloudy, it should be filtered first.

Make sure that any device you buy is:

Values in other countries

Health Canada’s recommendation of a minimum 99.9% reduction of Giardia and Cryptosporidium from the source water is comparable to the United States' requirement.

The World Health Organization recommends removing or inactivating enteric protozoa using an approach that is similar to Canada’s.

For more information

Guidelines for Canadian Drinking Water Quality: Enteric Protozoa: Giardia and Cryptosporidium.

If you have questions about the guideline or enteric protozoa in drinking water, you can contact us at:

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