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Cryptosporidium oocysts
Cryptosporidium is a protozoan (single celled) parasite which, if ingested, can cause an illness called cryptosporidiosis.
The main symptom in humans is watery diarrhoea, which can range from mild to severe. It is often accompanied by stomach pain, nausea or vomiting, fever and sometimes dehydration and weight loss.
It is a leading cause of human gastrointestinal infection in the UK. Young farm animals can also suffer from Cryptosporidium diarrhoea.
A number of different Cryptosporidium species infect animals. In humans, illness is mainly caused by Cryptosporidium parvum and Cryptosporidium hominis. In animals, illness is mainly caused by Cryptosporidium parvum.

Who gets it and how serious is it?

Anyone can become infected with Cryptosporidium, although illness is most common in children between 1 and 5 years of age.
Human infection occurs when Cryptosporidium oocysts (the hardy cyst stage of the parasite’s lifecycle) are taken in by mouth. The oocysts can survive in the environment and in water for long periods of time.
Human infection may be acquired by four main routes: from other people, from animals and their faeces, from untreated drinking water contaminated by either agricultural or human sewage sources, and from swimming in contaminated water. Infection is frequently associated with foreign travel.
Healthy people with cryptosporidiosis will recover without treatment although it is not unusual for the illness to last for up to three weeks. In individuals with severely weakened immune systems, serious, prolonged and potentially life-threatening illness may develop.


There is no specific treatment for cryptosporidiosis, and most patients will recover within a month.
The advice of a health professional should be sought in all cases of severe diarrhoea (especially in babies, children and the elderly). It is import to drink plenty of fluids in frequent small sips to avoid dehydration, which may be treated with oral rehydration therapy. 

How common is it?

Cryptosporidium is a leading cause of infectious diarrhoea in humans and in calves in the UK and is also associated with foreign travel.
Large community outbreaks of cryptosporidiosis may occur through contamination of public water supplies when physical elements of water treatment have been inadequate, and from exposure to contaminated recreational waters, especially swimming pools. 
Seasonal outbreaks of cryptosporidiosis are associated with farm visits to bottle-feed and handle lambs. Person to person spread, particularly within households and child care centres, may also account for a substantial proportion of cases.


Cryptosporidiosis is highly infectious so proper sanitation and good hygiene practices are important measures in the prevention of cryptosporidiosis. Such measures include: 
  • the proper treatment of water supplies
  • avoiding swallowing water when swimming
  • washing hands thoroughly with soap and warm water before eating or preparing food, after using the toilet, changing nappies or cleaning up after others with diarrhoea and after contact with domestic or farm animals
  • washing or peeling raw fruit and vegetables thoroughly before eating and avoiding unpasteurised milk and fruit juices
  • hand-washing when visiting open farms and only eating in designated areas
  • not using public recreational water facilities for two weeks after recovery.
There are five basic ways to manage diarrhoea and vomiting and prevent the spread of diseases:
  1. Careful handwashing is the most important prevention measure that you can take. Wash hands thoroughly with soap and warm water and dry afterwards. Do not share towels.
  2. Use gloves when handling soiled articles from ill people. Wash soiled clothing and bed linen on ‘hot cycle’.
  3. If looking after someone with gastroenteritis, carefully disinfect toilet seats, flush handles, wash-hand basin taps and toilet door handles daily and after use. Use a bleach-based household cleaner, diluted according to the manufacturer’s instructions.
  4. Maintain good personal hygiene and hygienic preparation and serving of food.
  5. If you have gastroenteritis, don’t return to school or work until you have been symptom-free for 48 hours. Don't visit patients in local hospitals and long-term care facilities. While many people tend to feel better sooner, illness can still be spread if they return to work or school within 48 hours since the last symptom.


Minimising impact in Wales

One important role of Public Health Wales is the collection and interpretation of data about the levels of infectious disease in the Welsh population.
Key infections, including Cryptosporidium, are under constant surveillance, to detect significant trends, to evaluate prevention and control measures, to identify and manage disease outbreaks and to alert appropriate professionals and organisations to infectious disease threats.
The Cryptosporidium Reference Unit, the reference laboratory for Cryptosporidium  and which provides specialist microbiology tests and services for England and Wales, is based at Public Health Wales Microbiology Swansea.

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Last updated: 04 April 2012