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Facts About...


What is it?

Cryptosporidium is a microscopic parasite responsible for causing an intestinal illness named cryptosporidiosis. This organism forms cysts called oocysts (pronounced “o-o-sists”) which are highly resistant to diverse environmental conditions. These oocysts are present in most surface water sources (e.g., lakes and rivers). In children, the incidence of cryptosporidiosis is greatest during the summer and early fall corresponding to the outdoor swimming season. Consuming food or water contaminated with Cryptosporidium oocysts can make you ill.

How is it spread?

Cryptosporidia live in the gut of many domestic and wild animals. Cryptosporidia form oocysts, which help the parasite, survive outside the body. Oocysts are in the stool of infected animals and people, and can live in a moist environment for 2-6 months. Water run-off from farmland washes oocysts into lakes, rivers and streams. Recreational use of water including waterslides, pools or lakes and consumption of contaminated beverages are common causes of cryptosporidiosis. Diaper changes, or contact with animal or human feces can also lead to infection if hands are not washed.

Southern Durham Region residents use Lake Ontario as their source of municipal drinking water. Beaverton uses Lake Simcoe. Both of these lakes may be contaminated with Cryptosporidium oocysts, especially during spring run off. All lake water supply systems in Durham Region receive multiple stage treatment. Coagulation, flocculation and filtration processes are critical for successful removal of Cryptosporidium. Staff at the municipal water treatment plants is well aware of the risk presented by this parasite and take every precaution to eliminate any breakthrough in the system.

What do I look for?

When infected with Cryptosporidia, most people will develop watery diarrhea. Abdominal cramps, loss of appetite and weight loss are also common. Nausea, vomiting and low fever occur less often. Recovery may take a few days to a few weeks. Other than drinking plenty of fluids, treatment is in general not required.

Infants, the elderly and people with weakened immune systems (e.g., HIV/AIDS, cancer, organ and bone marrow transplant patients) may develop severe illness. For people with these conditions, cryptosporidiosis diarrhea is difficult to treat. Significant weight loss, dehydration and body chemical imbalance may result. See your doctor if symptoms are prolonged or severe.

The incubation period for cryptosporidiosis is 2-14 days, with an average of 7 days.

How can I protect myself?

Wash your hands after defecation and changing diapers. Also, wash your hands before and after handling and eating food. Ensure hands are washed for a minimum of 15 seconds with warm water and soap and dry with a single use towel. If you have diarrhea, do not handle food for others until diarrhea has stopped for 24 hours.

Recreational swimming, even in chlorinated pools, can be a source of cryptosporidiosis. Always shower before entering a pool and avoid swallowing water while swimming.

If you have diarrhea, avoid using recreational waters for 2 weeks after symptoms have resolved.

If you have a weakened immune system, extra precautions should be taken:

  • Avoid drinking untreated water from lakes, streams, and rivers.
  • Avoid contact with feces (e.g., diaper changes, litter box/pooper scooper, anal sex).
  • When the safety of drinking water is doubtful, bring the water to a rolling boil for at least one minute prior to consumption. Bleach does not work well in killing off Cryptosporidium parasites.
  • Also, consider a water filter for water from non-municipal sources with a micron rating of less than 1 (called “Absolute”) to filter Cryptosporidium oocysts. Gloves can be worn to avoid direct contact with parasites contained in the filters.
  • As an alternative, bottled water may be considered. Be aware that bottled water varies according to source (e.g., wells, springs, municipal tap water) and unlike municipal supplies; there is no continual monitoring of a bottled water supply. Individuals should not presume that all bottled waters are absolutely free of Crypto.
  • A reverse osmosis or distillation water treatment device can be used.

Check manufacturer’s literature for treatment and maintenance specifications of the product. Also look for a National Sanitation Foundation (NSF) logo on the product. This symbol indicates that the product has been subjected to rigorous tests to ensure that the claims of the manufacturer are justified.

More information can be obtained from

Durham Region Health Department, Environmental Help Line 905-723-3818 or 1-888-777-9613

April 22, 2013