Key messages

  • Cryptosporidial infection is a Group B disease and must be notified. School exclusions also apply.
  • Cryptosporidiosis is a parasitic infection that commonly presents as gastroenteritis.
  • Cryptosporidium may be found in soil, food and water, or on surfaces that have been contaminated with faeces from infected humans or animals.
  • An outbreak investigation is required if two or more cases are clustered in a geographical area or institution.

Notification requirement for cryptosporidiosis

Cryptosporidial infection (Group B disease) must be notified in writing within 5 days of diagnosis.

This is a Victorian statutory requirement.

Primary school and children’s services centre exclusion for cryptosporidiosis

Exclude cases from primary school and children’s services until there has not been a loose bowel motion for 24 hours or until a medical certificate of recovery is produced.

Food handlers, healthcare workers and childcare workers should be excluded from work until diarrhoea has ceased.

Notification is required if Cryptosporidium spp. are isolated from water supplies.

Infectious agent of cryptosporidiosis

Cryptosporidium is a protozoan; it is a single-celled parasite that lives in the intestines of humans and other animals.

Cryptosporidium hominis and C. parvum are the two most common species causing disease in humans, although infections with C. felis, C. meleagridis, C. canis and C. muris have been reported.

Millions of cryptosporidia can be released in a bowel movement from an infected human or animal, and the number of cryptosporidia needed to cause infection is very low.

Identification of cryptosporidiosis

Clinical features

Cryptosporidiosis is a parasitic infection that commonly presents as gastroenteritis. Enteric symptoms usually include watery diarrhoea associated with cramping abdominal pain, dehydration, weight loss, fever, nausea and vomiting. The disease is usually mild and self-limiting (1–2 weeks). The symptoms may go in cycles in which the person seems to get better for a few days and then feels worse before the illness ends.

In people with impaired immunity, particularly those who are severely immunosuppressed, such as those with AIDS, the illness can be serious, prolonged and life-threatening. Cryptosporidium infection may less commonly involve the lungs (bronchitis or pneumonia), gall bladder (cholecystitis) or pancreas (pancreatitis).


As tests for Cryptosporidium are not routinely conducted in some facilities, laboratories should be informed if cryptosporidiosis is suspected.

Oocysts may be identified by microscopy of faecal smears treated with a modified acid-fast stain or safranin – methylene blue. Several stool specimens over several days may be required.

Oocyst excretion is most intense during the first days of illness. Oocysts are rarely recovered from solid faeces.

A monoclonal antibody test is useful for detecting oocysts in faecal and environmental samples.

ELISA assays have been developed for the detection of antibodies but are not in routine use.

Molecular methods can be used for speciation.

Incubation period of Cryptosporidium

The incubation period is estimated to be 1–12 days, with an average of 7 days.

Public health significance and occurrence of cryptosporidiosis

Cryptosporidiosis occurs worldwide. Young children, the families of infected people, men who have sex with men, travellers, healthcare workers and people in close contact with farm animals comprise most reported cases. Substantial outbreaks linked to public water supplies have been reported in the United States. Multiple outbreaks associated with public swimming pools and spas have been reported in Australia and worldwide. The risk of infection for Melbourne residents has been greater for people exposed to public swimming pools and household contacts of infected people.

Reservoir of Cryptosporidium

Reservoirs include humans, cattle and other domestic and feral animals.

Cryptosporidium may be found in soil, food and water, or on surfaces that have been contaminated with faeces from infected humans or animals.

Mode of transmission of Cryptosporidium

Transmission occurs by the faecal–oral route (person to person and animal to person), and via ingestion of contaminated foods and water.

Period of communicability of cryptosporidiosis

Cases may be infectious for as long as oocysts are excreted in the stool. Asymptomatic excretion may persist for several weeks after symptoms resolve.

Under suitable conditions, oocysts may survive in soil and be infective for up to 6 months.

Susceptibility and resistance to cryptosporidiosis

Everyone is susceptible to infection. People with normal immune systems usually have asymptomatic or self-limited gastrointestinal disease.

People with impaired immunity may experience prolonged illness.

Control measures for cryptosporidiosis

Preventive measures

Encourage good personal hygiene, particularly following contact with animals or infected people.

Particular attention to handwashing is required during calving seasons on cattle properties or when handling animals with diarrhoea.

Filter or boil contaminated drinking water, as chemical disinfectants such as chlorine are not effective against oocysts at the concentrations used in water treatment.

Control of case

Treatment is symptomatic and particularly involves rehydration. Treating clinicians should consult the current version of Therapeutic guidelines: gastrointestinal and seek expert advice.

If antibiotic treatment is indicated, nitazoxanidea is available from the Special Access Scheme.

Immunocompromised people, particularly those with HIV/AIDS, who are suspected of having cryptosporidial infection should seek medical advice, as nitazoxanide (an anti-protozoal) has not been shown to be superior to anti-retroviral therapy.

Safer sexual practices (barrier methods and frequent washing) can also reduce the risk of faecal–oral exposure.

Exclude symptomatic people from food handling, the direct care of hospitalised and institutionalised patients and the care of children in childcare centres until they are asymptomatic.

Clean and disinfect soiled articles.

As oocyst excretion may persist for extended periods, it is not advisable for cases to swim in public pools for 2 weeks after the resolution of symptoms. Showering before swimming is recommended at all times.

Control of contacts

The diagnosis should be considered in symptomatic contacts.

Control of environment

Faecal contamination of pools requires prompt action by the pool operator, including disinfection, but oocysts resist standard chlorination. Refer to the department’s specific Cryptosporidium guidance in the ‘Water’ section and general guidance in the Pool operators’ handbook.

Outbreak measures for cryptosporidiosis

An outbreak investigation is required if two or more cases are clustered in a geographical area or institution. Investigate potential common sources, such as:

• contact with farm animals

• exposure to a common food (beverages, salads or other foods not heated or cooked)

• exposure to a facility (for example, childcare centre, healthcare facility or institutional setting)

• exposure to a recreational water source (swimming pool, hot tub, fountain, lake, river, spring, pond or stream) that may be contaminated with sewage or faeces from humans or animals.

The department considers that cases may be linked to a food, water or environmental source if two or more people with Cryptosporidium infection (confirmed by a pathology laboratory) have been at the same source within 2 weeks of their illness.

The owner of an affected swimming pool may need to close the pool until it has been treated and superchlorinated in accordance with the department’s Pool operators’ handbook.

Detailed guidance for swimming pool managers specific to cryptosporidiosis can be found in the ‘Water’ section, which includes a number of valuable resource materials on cryptosporidiosis and aquatic facilities, including brochures, posters, stickers and web links.


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