NORTH West Water is pumping £300million into eradicating a bug which caused severe stomach infections across the Ribble Valley last month.

Cryptosporidium -- a micro-organism which can make its way into water supplies especially in rural areas -- was found in water being supplied to more than 10,000 homes in Clitheroe, Chatburn, Downham, Worston and Barrow.

A total of 55 cases of the severe stomach infection, which causes abdominal pain and diarrhoea, were recorded by East Lancashire Health Authority during March.

Water supplies were changed from the Lowcocks water treatment works at West Bradford to the Hodder works, but householders were advised to boil drinking water for more than a week. The water company is now working with the health authority and the Drinking Water Inspectorate to pinpoint how the bug got into the domestic supply, but early investigations suggested that cattle, which carry cryptosporidium in their guts, had been near the reservoir.

NWW's findings are due to be published in a few months.

The five-year multi-million pound upgrade of 50 treatment works across the North West was sparked by an outbreak of the bug in homes served by the Thirlmere reservoir in April last year.

More than 280 people suffered cryptosporidiosis in North West Lancashire, South Lancashire, Bolton, Wigan, Salford and Trafford.

Work is now under way on a major programme of improvements to protect against cryptosporidium, which includes sophisticated monitoring systems, 'bubble mixing' which stirs reservoirs to prevent concentrations of the organism from building up and changing grazing practices for sheep and cattle around reservoirs.