Cryptosporidium and water
Cryptosporidium is a small parasitic organism that infects the small intestine of a number of mammals, including humans, leading to the illness cryptosporidiosis.
Cryptosporidiosis is characterised by diarrhoea, vomiting, stomach cramps and fever. In patients whose immune system is already weak such as those with AIDS, or the elderly, the disease can be more serious. There is still no effective treatment.
How is cryptosporidium transmitted?
Cryptosporidium can be passed from one infected person to another by contact with an infected animal, or from contaminated food and water.
The life cycle of cryptosporidium
Cryptosporidium is present in water environments, usually in small numbers. It is also found more commonly in surface waters than in groundwaters.
It exists outside the host as oocysts (a thick-walled structure in which parasites develop) and is closely associated with livestock. Oocysts are very resistant to difficult conditions and can lie dormant for months in cool moist environments.
The life cycle begins when the host ingests the oocyst. The entire life cycle takes place within one host and then oocysts are shed in the faeces of the affected individual. When swallowed by another animal, a new cycle of infection begins.
Cryptosporidium and water treatment
Conventional water treatment is normally an effective barrier against cryptosporidium. However, one of the main problems with the treatment of cryptosporidium is its resistance to standard chlorine disinfection techniques.
Action against cryptosporidium
Like the rest of the U.K., new arrangements for monitoring cryptosporidium were introduced in 2000. These new arrangements enabled detection standards to be established for public health protection.This included a formal notification level to the health authorities of one or more cryptosporidium oocysts per 10 litres of water, and an alert level of 0.1 oocysts in 10 litres.
The World Health Organisation have published a guide to cryptosporidium risk assessments (.PDF 1.43Mb)
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