Inadequate treatment of drinking water

Inadequate treatment of drinking water at risk of Cryptosporidium

What is Cryptosporidium?

Cryptosporidium is a microscopic parasite (organism) that lives in the gut of infected humans and animals.

How can Cryptosporidium affect my health?

  • Cryptosporidium infection (called cryptosporidiosis) causes watery diarrhoea.
  • Other symptoms include stomach cramps, fever, nausea and vomiting. Some people may have no symptoms at all.
  • Symptoms usually begin 2 to 10 days after becoming infected.
  • People in good health usually recover in 1 to 2 weeks.
  • Symptoms can be more severe in young children and elderly people.
  • The infection can be serious in people who have weak immunity (those on cancer treatment or those with HIV infection).

Where is Cryptosporidium found in the environment?

The parasite leaves the gut of infected animals and humans as an oocyst in faeces (poo). This is how Cryptosporidium is released into the environment.

An oocyst has an outer protective wall (like a cyst) that allows the parasite to survive outside the body for a long time.

Cryptosporidium can be found in soil, water, food, or surfaces that have been contaminated with animal or human faeces.

It is more common in rural environments.

How is Cryptosporidium spread?

It is spread by swallowing anything that has become contaminated with the Cryptosporidium oocyst in the environment (whether soil, water, food or contaminated surfaces).

It survives easily in water. It can be spread by swallowing contaminated drinking water or contaminated water from a swimming pool, jacuzzi, lake or river.

Cryptosporidium is more likely to be found in drinking water that comes from a surface water supply (water from lakes and rivers).

Surface water supplies are therefore more ‘at risk’ of Cryptosporidium contamination than groundwater supplies (wells).

Why does Cryptosporidium survive in water?

The outer protective wall of the Cryptosporidium oocyst allows it to survive outside the body for a long time in a cool wet environment.

Oocysts are not destroyed by chlorine which is used to kill other biological organisms (bugs) in drinking water.

Other methods are therefore needed to remove oocysts from contaminated drinking water or to inactivate them.

How are Cryptosporidium oocysts removed from drinking water?

Cryptosporidium oocysts can be removed from water by:

  • filtration - a process that filters the water and removes oocysts at the water treatment plant
  • ultraviolet (UV) light water treatment - a process that kills oocysts. Dead oocysts do not cause illness
  • other, less common types of treatment

I have been told my water supply has inadequate treatment for Cryptosporidium. What does this mean?

If a water supply has inadequate treatment for Cryptosporidium it means that:

  • your supply is at risk of being contaminated with Cryptosporidium
  • there may be no filtration or ultraviolet (UV) light treatment or other treatment in place  

This does not necessarily mean that there are Cryptosporidium oocysts in your water.

It does not mean that you will become ill with Cryptosporidiosis.

It does not mean that you need to boil your water.

If your health is severely immunocompromised you may wish to boil your water regardless of your drinking water supply. See below for more detail*.

If my water supply has inadequate treatment for Cryptosporidium, should I be concerned about the risk of Cryptosporidium infection?

It is important that you are aware of what happens to protect people on any water supply with inadequate treatment for Cryptosporidium.

If you are on a regulated drinking water supply your water may be monitored or tested regularly for Cryptosporidium oocysts by the Water Services Authority. The HSE is alerted if there is any cause for concern.

Rates of notified Cryptosporidiosis in the community are routinely monitored by Public Health Departments in the HSE.

If consumers of a particular water supply are considered to be at an increased risk of cryptosporidiosis illness, or if a cluster or outbreak of illness is detected, a Boil Water Notice will be issued by the Water Services Authority in consultation with the HSE.

Such preventive action helps protect the public from illness and applies to all water supplies.

*If your health is severely immunocompromised you may wish to boil your water regardless of your drinking water supply. Not every immunocompromised person needs to do this. Public Health medical specialists have issued detailed advice for considering this option with your GP or Consultant.

If you are on an unregulated water supply (a small group supply or a private well) and are concerned about your water quality you should assess your water supply for risk of illness.

 Where can I find more information about Cryptosporidium in drinking water and about Cryptosporidiosis?

More information about Cryptosporidiosis from the HPSC  

For more details about your drinking water quality you should contact your water supplier: