HSE warns of threat of cryptosporidium and giardia to those affected by boil water notice in Leinster 1 year ago

HSE warns of threat of cryptosporidium and giardia to those affected by boil water notice in Leinster

Drinking the water may cause gastrointestinal infections with symptoms including diarrhoea and stomach cramps.

The HSE has issued advice for anyone affected by the recent boil water notice issued by Irish Water.


Following issues at a water treatment plant in Leixlip, 600,000 people are expected to be affected by potential contamination with water supplies in north Dublin city and county, parts of south Dublin County Council area, north Kildare and parts of east Meath at risk.

On Wednesday, an Irish Water spokesperson told Morning Ireland that the boil water notice is expected to remain in place for a day or so.

The affected areas can be seen here.

As a result, drinking water produced at the water treatment plant may contain cysts of cryptosporidium and giardia.

The HSE says this may cause gastrointestinal infections with symptoms including diarrhoea and stomach cramps. People who develop such symptoms should consult their GP for testing and treatment.

Cryptosporidiosis is a diarrhoeal disease caused by a microscopic parasite (cryptosporidium).

Once an animal or person is infected, the parasite lives in the intestine and passes in the stool. The parasite is protected by an outer shell that allows it to survive outside the body for long periods of time and makes it very resistant to chlorine-based disinfectants. It can survive temperatures greater than 70oC. It is found through the world, particularly in water.


Cryptosporidium lives in the intestine of infected humans or animals. Millions of parasites can be released in a bowel movement from an infected human or animal.

It is therefore found in soil, food, water, or surfaces that have been contaminated with human or animal faeces. It is a common cause of waterborne outbreaks of gastroenteritis.

The most common symptom of cryptosporidiosis is watery diarrhoea. Other symptoms include:

  • Dehydration
  • Weight loss
  • Stomach cramps or pain
  • Fever
  • Nausea
  • Vomiting

Some people with cryptosporidiosis will have no symptoms at all. Symptoms of cryptosporidiosis generally begin two to 10 days (average seven days) after becoming infected with the parasite.


In persons with healthy immune systems, symptoms usually last about one to two weeks.

The symptoms may go in cycles in which you may seem to get better for a few days, then feel worse again before the illness ends. It is a mild disease in healthy people. It is often more severe in small children and elderly people and can be very serious in those people who are immunocompromised (such as patients undergoing cancer treatment and those living with HIV).

Cryptosporidium can be quite contagious. However, these measures will reduce the likelihood of spread:

  • Wash your hands with soap and water after using the toilet, changing nappies, and before eating or preparing food.
  • Do not swim in recreational water (pools, hot tubs, lakes or rivers, etc.) if you have cryptosporidiosis and for at least two weeks after diarrhoea stops. Cryptosporidium can be spread in a chlorinated pool because it is resistant to chlorine.

Giardiasis is a form of gastroenteritis, characterised by diarrhoeal illness that is caused by a microscopic parasite, giardia lamblia.

Giardia lamblia lives in the intestines of humans and many animals. Giardiasis occurs when the parasites are ingested, most commonly when contaminated water containing the parasites is drunk.

Contaminated water may come from lakes or ponds, swimming pools, contaminated drinking water or ice. It may also be passed if the contamination is on food and environmental surfaces. It is resistant to the level of chlorination in drinking water.

Symptoms occur between seven to 10 days (usually one to three days) after exposure to giardia. Symptoms include:

  • diarrhoea
  • foul smelling greasy stools
  • flatulence
  • nausea

Diarrhoea can be prolonged leading to temporary malabsorption. Many cases are asymptomatic.

Diagnosis is based on finding giardia cysts in the stool of patients. Three samples are often needed as it may take three sets of stools to identify the parasite.  Antibiotics are effective against giardia.

Any person who has been diagnosed with giardiasis should practice scrupulous hand hygiene at home and in work as giardia can be readily passed between people. People can return to work once their bowel motions have been solid for 48 hours.

Further information on cryptosporidium and giardia is available on the HSE Health Protection Surveillance Centre website via the following links: cryptosporidiosis and giardiasis.