Introduction to Cryptosporidium



Cryptosporidiosis is an infectious diarrhoeal disease caused by a waterborne protozoan parasite. It is a disease of humans and animals, including cattle and sheep. Cryptosporidiosis cases have been declining in the UK for many years, but there are still around 4000 recorded cases each year in England and Wales.

Cryptosporidium most commonly affects young children and the immunocompromised, but can affect anyone. Cryptosporidium is found in the gut of man and animals (particularly cattle and sheep). It is also found in water contaminated with faeces.

It can be transmitted via contact with infected animals, by drinking or swimming in contaminated water and by eating contaminated food, e.g. salad vegetables. It can be spread from person to person where there is poor hygiene.

Occupations where there may be a risk of occupationally acquired cryptosporidiosis include workers in outdoor leisure industries in contact with water.

The incubation period is 2–10 days (average 7 days). The main symptom is watery diarrhoea, but symptoms can also include fever, stomach cramps and vomiting. Anyone with severe symptoms should seek medical attention. There is no treatment apart from rehydration therapy and most people recover within one month.

Cryptosporidiosis is a predominantly waterborne disease with infections caused by contaminated drinking water, swimming pools, water features, natural waters, or acquired by animal and human contact and a range of other routes. Cryptosporidium is a particular problem for swimming pools and drinking water because the oocysts are resistant to chlorine based disinfectants.

Swimming pool contamination is likely to occur all year round, but outbreaks are more common in the late summer period; this may be as a result of people using swimming pools more and also linked to holiday travel. Swimming pool outbreaks result from contamination of the water with cryptosporidium oocysts, usually from young swimmers.

Swimmers need to make sure they:

  • shower before swimming
  • do not swim if they have diarrhoea
  • try not to swallow pool water

Cryptosporidia is a parasite that is of particular concern for pool plant operators because it is not killed by chlorine. The parasites live inside a protective shell called an oocyst which protect them from the chlorine in the swimming pool or spa water. If these oocysts are ingested by swallowing contaminated water, the cryptosporidia with hatch out of the shells and reproduce, causing a gastro-intestinal illness. When the newly-created oocysts are expelled from the body via the faeces, the whole cycle starts again.