Cryptosporidiosis, often referred to as ‘crypto’ is an infection of the bowel caused by the parasite Cryptosporidium parvum.

How it is spread

Spread can occur by eating food or drinking water that has been contaminated by very small amounts of faeces from infected people or animals.

Infection can occur also from consuming unpasteurised dairy products.

Cryptosporidium is relatively resistant to chlorine disinfection and therefore can be spread through contaminated swimming or wading pools.


The symptoms generally develop between 1 to 12 days, with the average being 7 days after the person is infected.

The most common symptom is watery diarrhoea, which often occurs with stomach cramps. Other symptoms may include loss of appetite, nausea, vomiting, headache and mild fever. 

Healthy young children generally recover within a few days. Healthy adults generally recover within 4 weeks but may have periods of seeming to be better then becoming worse again during this time. People with weakened immune systems may develop a more severe and longer lasting illness.

Some people infected with Cryptosporidium may have no symptoms or only a brief episode of diarrhoea.

What is the infectious period

While the Cryptosporidium parasite remains in their faeces, infected people can pass the infection on to others. This is usually while they are ill and up to 2 months after their illness has resolved.

Who is at risk

The most severe infections occur in people with weakened immune systems (e.g. people on steroids or chemotherapy and those with HIV/AIDs).

Children who attend childcare facilities are at greater risk of infections spread through faecal contamination. 

Spread occurs when children share toys or food that have been contaminated and place it in their mouths. Particular care has to be taken wherever there are children in nappies.

Travellers, animal handlers and men who have sex with men are also more at risk of infection.


Antibiotics are generally not recommended for cryptosporidiosis.

Management focuses on preventing and treating dehydration caused by vomiting or diarrhoea. Anyone with vomiting or diarrhoea should drink extra fluids to avoid dehydration. Rehydration therapy with oral glucose/electrolyte solution is particularly effective. If children refuse this solution, diluted fruit juice may be given (1 part juice to 4 parts water).

Babies should continue to be offered their normal feeds plus extra fluids in between feeds.

Children with diarrhoea, who vomit or who refuse extra fluids should see a doctor. Anyone with prolonged or severe diarrhoea, or who have symptoms causing concern, should see a doctor.

Medicines to prevent vomiting or diarrhoea should not be given, especially to children, except where prescribed by a doctor.

How cryptosporidiosis can be prevented

Good hygiene is the best way to prevent cryptosporidiosis. 

Hands should be washed thoroughly with warm soapy water:

  • after going to the toilet
  • before preparing or handling food
  • after every nappy change
  • after changing soiled linen
  • after contact with pets or farm animals
  • after gardening or other direct contact with soil.

Other measures include:

  • never changing nappies on tables or counters where food is prepared or eaten
  • cleaning change areas with warm soapy water and disinfectant after every nappy change
  • cleaning books, toys, equipment, furnishings, floors and toilets regularly (including toilet door handles)
  • not consuming unpasteurised milk and untreated or inadequately filtered water
  • washing and/or peeling fruit and vegetables before eating them.

How it can be controlled

Anyone with diarrhoea should not attend childcare/school until there has not been a loose bowel action for 24 hours. People with diarrhoea should not prepare or handle food that will be eaten by others.

Anyone with cryptosporidiosis should not swim, wade or paddle in public pools for at least 2 weeks after the diarrhoea has resolved.

Doctors and public health workers are interested in preventing outbreaks of diarrhoea. If there are 2 or more cases of diarrhoea in a group, these should be reported to the local Centre for Disease Control.


For more information contact your nearest Centre for Disease Control.

Last updated: 12 May 2016

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