Cryptosporidium is a waterborne parasite, which can cause an unpleasant illness called cryptosporidiosis. The symptoms are diarrhea, mild abdominal pain, nausea, vomiting, mild fever and fatigue. Outbreaks of cryptosporidiosis have been caused by poor hygiene, contact with farm animals, contaminated drinking water and contaminated swimming pools. The review summaries the incidence and principal causes of the disease, and the measures employed by UK water suppliers to prevent infection via the water supply route.
Revised December 2011 (First published November 2001)
Cryptosporidium is a parasite which can produce an unpleasant gastric illness known as cryptosporidiosis. The parasite is transmitted in an encysted form known as an oocyst. At present there is nothing to treat cryptosporidiosis other than the body’s defence systems. Cryptosporidiosis can, therefore, be a serious problem in people with weak immune systems such as young children, the elderly, people on cytotoxic drugs and those suffering from AIDS. Cryptosporidium is the third leading cause of non-viral gastrointestinal illness in the UK.
There are several different species and strains of the parasite, but those which can infect human beings are also capable of infecting some animals, and vice versa.
Cryptosporidium is frequently waterborne in natural waters and infections have occurred from drinking contaminated water supplies. However, there are many other possible sources of infection such as zoonosis (animal-person contact), contaminated food and contaminated swimming pools and other recreational waters (rivers and lakes), or foreign travel.
A well-operated drinking water treatment plant can physically remove over 99.99% of oocysts from affected raw water. Traditional processes such as coagulation, clarification and filtration remain the best defence against this parasite entering supplies. However, high-risk sites are required to remove or render harmless any oocysts present based on raw water analysis and site-specific risk assessments.
Chemical disinfectants are not generally effective against Cryptosporidium however a barrier method (membranes) and/or UV treatment are the only truly effective treatments at high-risk sites.
Since 2007 in the UK the regulations are no longer specific for the control of Cryptosporidium, however, water companies are now required to design and continuously operate adequate treatment and disinfection. Any oocysts found in the final treated water need to be reported to the DWI so the inspectorate can make checks to confirm if the regulations were contravened or any offences were committed.
