Irish Water and Mayo County Council are investigating the cause of cryptosporidium contamination which has affected drinking water supplies for almost 47,000 people across south Co Mayo.

A boil water notice has been issued for all major towns in the south of the county, including Castlebar, Westport, Claremorris, Ballinrobe, Ballyhaunis and Knock, following the detection of the parasite in the the Lough Mask Regional Water Supply Scheme.

The communities of Ballindine, Balla, Kilmaine, Cong and a number of group water schemes are also covered by the boil water notice, which was issued on Friday night following advice from the Health Service Executive (HSE).

Irish Water says that a routine weekly sample from the Lough Mask water treatment plant detected the presence of cryptosporidium, which can cause gastrointestinal illness.

The agency and the local authority have apologised for the inconvenience to residents.

Priority customers

Irish Water regional information specialist Sean Corrigan said that “self-declared” priority customers supplied by the water scheme would be contacted directly by telephone to explain the situation, as public health was its “number one priority”.

Irish Water is liaising with the HSE and the Environmental Protection Agency and an incident management team had been set up, the agency said.

Mayo County Council’s county manager Peter Hynes told The Irish Times that the priority was to identify the source of the contamination.

Due to the vast area of the county covered by the boil water notice, the delivery of water in tankers was not yet being considered as an option, he said.

Major healthcare institutions, including Mayo General Hospital, will have to take precautionary boil water measures for drinking water, any water used in preparing salads and similar foods, teeth-brushing and ice-making.

Irish Water said boiled water should be covered and stored in a refrigerator or cold place, and warned that domestic water filters will not render the water safe to drink.

It said that ice cubes in fridges and freezers and any filtered water in fridges should be discarded.

It said water could be used for personal hygiene, including baths, but caution should be taken when bathing children to ensure they do not swallow water.

Infant feeds should be prepared with water that has been brought to the boil once and cooled, and water should not be reboiled several times.

Diarrhoea

Irish Water said anyone suffering from diarrhoea for more than two days should contact their general practitioner and provide a stool sample for testing, while making sure to drink plenty of boiled or bottled water.

The incident is the first major contamination in this scheme.

In 2007, some 120,000 people in Galway city and county were affected by a boil water notice due to cryptosporidium contamination.

A map and a list of the affected areas in south Mayo are available on the websites of Irish Water and Mayo County Council.

Irish Water says that further information and additional advice is available on www.water.ie or by calling 1890-278278.