Cryptosporidiosis (Cryptosporidium parasite)

What is it?
Cryptosporidium means 'hidden spore', it is a microscopic parasite found in the faeces of infected humans or animals. It is transmitted via contaminated water and food or through touch of contaminated objects (to be caught in this way the victim must touch their mouths before washing their hands to be infected). The Cryptosporidium parasite is very hard to detect. Although it is reasonably rare in well maintained water systems, it is small enough to pass through most filtration systems and survives chlorination and other disinfectants*. Cryptosporidiosis (the disease caused by the parasite) has no cure.

How is it caught and what happens?
It can be caught through drinking and eating infected water and food. The cryptosporidium spore cannot multiply in food or water; it needs an animal or human host to do this. Once the spore is ingested it attaches itself to the gut wall and reproduces. The spores complete their life cycle in one host and are then excreted.

In healthy adults symptoms of cryptosporidiosis normally develop after 2 - 10 days of ingesting the parasite and include watery diarrhoea (which lasts from 1-2 weeks), abdominal cramps, fatigue, nausea, vomiting and fever. Cryptosporidiosis can be chronic and life threatening in those with weak immune systems due to illness, surgery or immunosuppressive drugs. There is no known cure for the condition, but in some cases drugs can reduce the symptoms.

If you think you have developed cryptosporidiosis contact your doctor immediately and make him/her aware of your suspicions.

Who is at risk?
Those who come into contact with infected water, food and excrement are at risk. Like many diseases and illnesses, those with weakened immune systems are at a higher risk of Cryptosporidiosis. The Government highly recommends that those with weakened immune systems should boil tap and bottled water for drinking and cooking before use.

You are at a higher risk if you work with animals (particularly lambs and calves), work with children - especially those of nappy wearing age, care workers/nurses etc who may come into contact with the excrement of people suffering from cryptosporidiosis, those who come into contact through work or recreation with contaminated water, those who handle contaminated raw food and those who may come into contact with faeces through sexual practices.

As the spore is carried in drinking water and food, it often strikes communities. It can strike from dozens to thousands of people in these community outbreaks.

If you are travelling to a developing country, the risks of water and food being contaminated are high. Use bottled water but make sure that the bottled water has been treated to a level adequate to kill cryptosporidium.

Those who use private water supplies may be at a higher risk as these supplies may have less advanced filtration systems and may be tested less often.

Protecting against cryptosporidiosis
The cryptosporidium spore can live for up to 18 months in a cool, damp or wet environment, including reservoirs and pipes. It is very hard to destroy and is resistant to disinfectant. In very high levels disinfectant can affect the spores, but such levels cannot be used in water intended for drinking. At temperatures of below 0°C, cryptosporidium is killed, at temperatures above 65°C the spores are rendered harmless.

The cryptosporidium spore is very small (approx 4-6 µm diameter) and therefore passes through most filtration systems. Flocculation and slow sand filtration systems are believed to be the most effective form of filtration against cryptosporidium. If you filter water in your home, make sure you use one which filters water to 1µm pore size. Equally if you buy bottled water look for labels that say it has been filtered to 1µm pore size (not all filtered water will have been filtered to this level), distilled or been treated by reverse osmosis to ensure the spore has been removed.

If you have a low immune system you should boil all water used for cooking and drinking for 1 minute.

If you handle raw meat, fruit or vegetables, please be aware that if they have come into contact with contaminated water, they too are at risk of contamination. Those with a low immune system should peel fruit and vegetables. Always wash your hands immediately after touching raw meat, never touch your mouth. It is believed cooked foods are not at risk.

Always wash your hands after using the toilet or before eating and drinking.

UK water companies
The UK Drinking Water Inspectorate (DWI) has found that most outbreaks of cryptosporidiosis are normally related to "inadequate provision or poor operation of water treatment." Water treatment can be very effective in providing protection against cryptosporidium; the DWI states that there is good evidence to suggest that, "careful operation of the coagulation/flocculation and filtration processes provides consumers with a very high level of protection against exposure to the parasite".

In the UK, water companies have to by law carry out risk assessments to discover the risk of cryptosporidium contaminating water supplied from their treatment works. If there is a risk, the water companies must ensure (through water treatment) that the number of cryptosporidium present reaches no more than 1 spore per 10 litres of water. To ensure water companies comply with the standard, they must use a regulatory method for sampling and testing the water. Research has suggested that very frequent analysis of water samples for cryptosporidium is the most effective way of testing for the parasite.

What is an acceptable level of cryptosporidium in drinking water?
Although there is no health-related standard for the amount of cryptosporidium in drinking water, the treatment standard of 1 spore per 10 litres of water ensures that water companies are careful to keep their water treatment processes to high standards. There are two main reasons why no health-related standard is in place:

• there is a wide variation people's susceptibility to cryptosporidiosis. Different people are affected by different levels of the spore;
• little is known about the spore's ability to cause infection.

It has been noted that cryptosporidiosis breaks out when spores are higher in number than 1 spore per 10 litres of water.

The Third Report of the Expert Group on Cryptosporidium in Water Supplies
In 1998 the Drinking Water Inspectorate published The Third Report of the Expert Group on Cryptosporidium in Water Supplies (often referred to as the Bouchier Report), which highlighted several points on the control of cryptosporidium. The report recorded that:

• water related outbreaks of cryptosporidiosis broke out in situations where the water treatment process was inadequate, or where its operation was not satisfactory, or where the treatment process was overloaded;
• cryptosporidium has a high resistance to disinfection;
• treatment barriers should be checked with turbidity monitoring to ensure proper working - in most outbreak situations, turbidity peaks were present in the treated water after leaving the treatment works;
• not all groundwater is of a consistent high quality - there is a risk of cryptosporidium contamination;
• it is impossible to recommend a health-related standard for cryptosporidium in drinking water - different people are affected by different levels of the parasite;
• people with low immune systems should always boil all tap and bottled water before drinking or using for cooking.

The report pointed out that there is still a lot to learn about the cryptosporidium parasite. The spore was only discovered in the 1970s and we still know relatively little about it.

Regulations covering cryptosporidium
The government has put into place several regulations to ensure that drinking water in the UK does not contain harmful amounts of cryptosporidium. A brief overview of Regulations are as follows:

The Water Supply (Water Quality) (Amendment) Regulations 1999

• water companies have to make a risk assessment of the likelihood of contamination from cryptosporidium in water supplied from their treatment works;
• if there is a risk, water companies have to treat the water to ensure the number of spores does not exceed 1 spore per 10 litres of water;
• water leaving treatment works must be continuously tested for cryptosporidium.

The Water Supply (Water Quality) Regulations 2000 (SI 2000/3184)

• water companies have to make a risk assessment of the likelihood of contamination from cryptosporidium in water supplied from their treatment works;
• if there is a risk, water companies have put in measures (normally filtration) to contain the risk to ensure the number of spores does not exceed 1 spore per 10 litres of water;
• water leaving treatment works must be continuously sampled and analysed for cryptosporidium;
• breach of regulations is a criminal offence.

The Water Industry Act 1991

• it is an offence (subject to a due diligence defence) for a water company to supply water unfit for human consumption.

Want to know more?
For more information please visit the Drinking Water Inspectorate's website www.dwi.gov.uk

If you have a low immune system, ask your doctor or health care worker about the precautions you should take to protect yourself from cryptosporidium.