Cryptosporidiosis (Cryptosporidium): For health professionals

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What health professionals need to know about cryptosporidiosis

Cryptosporidium is a parasite that occurs worldwide. There are several species of Cryptosporidium but only Cryptosporidium parvum is known to cause illness in humans.  Cryptosporidiosis is in the top 5 most common causes of infectious diarrhea around the globe.

Cryptosporidium parasite can be spread by:

  • exposure to contaminated soil
  • eating or drinking contaminated food or water
  • touching surfaces that have been in contact with feces of infected humans and animals

Contaminated water is the most common cause of illness. 

The majority of cases are sporadic. Past outbreaks in Canada have been linked to swimming in and drinking contaminated recreational water.

Clinical manifestations

The most common symptom of cryptosporidiosis is acute watery diarrhea with stool volumes that may exceed 3L per day.

Other symptoms could include:

  • fever
  • cough
  • fatigue
  • nausea
  • eye pain
  • vomiting
  • dizziness
  • joint pain
  • dehydration
  • recurrent headache
  • intestinal inflammation
  • stomach cramps or pain

Symptoms can last anywhere from a few days to a month. Recurrence of symptoms can occur among cases. Although the illness is usually self-limiting, it may persist in immunocompromised patients. Children and immunocompromised adults are at the greatest risk for severe and prolonged illness.

Some people with Cryptosporidium may have no symptoms. 

In those with weakened immune systems Cryptosporidium infections could develop into serious, chronic and sometimes fatal illness, such as:

  • severe dehydration
  • significant weight loss
  • inflammation of the:
    • liver
    • pancreas
    • gallbladder


Direct microscopic observation of ova and parasites in stool specimens is the usual form of detection. Nucleic acid and antigen detection methods have also been developed.


Most people will recover without treatment.  Illness is generally self-limiting in immunocompetent patients. Young children and pregnant women may be more susceptible to dehydration.

Severe diarrhea can be treated with:

  • antimotility agents
  • electrolyte therapy
  • nutritional support
  • oral or intravenous rehydration

Anti-retroviral therapy is currently considered the best treatment option in AIDS patient to help decrease or eliminate symptoms of cryptosporidiosis.


Health professionals in Canada play a critical role in identifying and reporting cases of cryptosporidiosis. See the surveillance of the cryptosporidiosis section for more information on surveillance in Canada.

Consult the national case definition for additional information

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