Water in Galway city and county has been given the all-clear and is now deemed safe to drink.
There have been no new cases of cryptosporidiosis, the gastrointestinal illness caused by the parasite, in several weeks.
The bug was first found in the water supply in January, and the boil-water notice covering Galway city and part of Galway county was issued on March 15th.
Up until today around 70,000 people in the city and parts of south Connemara had to boil their water for food preparation and consumption.
The Environmental Health Department has sent letters to managers of food premises, swimming pools, nursing homes and schools informing them they no longer need to boil tap water and offering advice on machinery and equipment where relevant.
The Public Health Department has contacted GPs, dentists, pharmacists, pre-schools, schools, hospital managers and public health nurses to advise them.
Galway City Council and Galway County Council will provide a helpline for further questions relating to the water supply. This number is 091 536400 (office hours).
Minister for the Environment John Gormley welcomed the announcement today.
He said he is very aware of the inconvenience, distress and anxiety that suchboil notices, necessary though they may be to protect public health, cause to everybody affected by them.
"My Department had worked closely with the City Council and provided whatever assistance it could towards resolving the problem whether by way of advice, financial assistance or staffing," Mr Gormley said.
"I want to ensure that this close co-operation continues and that we all learn from this incident. I am particularly anxious to see that we continue the substantial investments, as set out in my Department's Water Services Investment Programme, in protecting and enhancing our valuable water resources."
Mr Gormley said his Department and the Environmental Protection Agency are now working together on measures to resolve water quality issues in public water supplies and to identify any additional infrastructural upgrades that may be required to deal with the cryptosporidium issue.