WATER bosses have claimed that cases of cryptosporidiosis - caused by a dangerous microscopic parasite that could be present in Bolton's water supply - are relatively uncommon in Britain.

A statement issued by North West Water said the condition affected 5,000 people last year - a small number, it claimed, when compared to more than 50,000 notified cases of the most common form of food poisoning.

The BEN has received a large volume of calls from people in Bolton whose symptoms match those that are said to result from the bug cryptosporidium, but Dr Robert Aston consultant in communicable diseases for Wigan and Bolton said up to five per cent of the town's population suffers different types of stomach bugs every week. One of the victims of the cryptosporidiosis bug was David Higgin from Halliwell who had his illness identified by a doctor.

The 53-year-old became ill last Christmas and went to see a doctor before being referred to a gut specialist. He was given tablets for his diarrhoea - the most common symptom - and samples were taken away for analysis.

His wife, Kathleen, 54, said: "He was very ill and I was so worried. The reason for his illness was found by accident when his samples were sent to a pathologist by mistake and he identified it.

"My husband lost a stone in weight. We didn't know what to think when it all happened. All sorts go through your mind, like cancer of the bowel. It was a worrying time." Mr Higgin suffered from fatigue and he had a fever - two of the more rare symptoms of the disease.

Mrs Higgin added: "He was very tired and when he went to the doctor we had to get him from his bed and carry him to the taxi. He was sitting in the waiting room and falling asleep in his seat. His illness lasted for about three weeks.

"When it happens you think all kinds like why it happened to him and not the rest of us as well."

Cryptosporidium exists in a form called oocyst less than one tenth the thickness of a human hair.

It is commonly found in cattle, sheep, foals, goat kids and deer calves as well as humans. Symptoms include diarrhoea, nausea, vomiting, fever, headache and loss of appetite. There is no effective treatment for it.

According to North West Water the bug can enter the water supply through the excrement of animals which is washed into rivers and streams and, in turn, reservoirs.

In 1997 there was a large outbreak of the bug covering large areas of North-west London and Hertfordshire.

Mike Neale of Pictons Solicitors in Watford said he handled more than 450 claims for compensation against the water company involved.

He said he is also acting on behalf of a number of children who have been similarly affected by an earlier outbreak in an area covered by North West Water.

Henry Walker, 86, and his wife, Brenda, 80, also contracted the illness this year. Their trouble started on April 9 and lasted for three weeks.

Mr Walker said: "I came back from the pub and went to bed. At six o'clock the next morning I woke up and by eight o'clock I'd been to the toilet three times. It continued for five days and I had a temperature. My legs were weak and I had to sit down a lot."

Medical experts are investigating seven cases reported to health chiefs over the past fortnight.

They are looking into a possible link with Thirlmere Reservoir in the Lake District, which supplies drinking water to Bolton.

North West Water said it was investing in independent scientific research in Britain and overseas with a £300 million programme under way to target further improvements at more than 50 water treatment works by upgrading and introducing new technology. James Chadwick, a 20-year-old Newcastle University student, from Westhoughton, said he felt his exam performance could be in jeopardy after he went down with the bug just a week after returning to the North-east from Bolton.

His mother, Dorothy, said: "He had tests in Newcastle and it was confirmed that he had cryptosporidiosis. He'd been in Bolton for four weeks over Easter and I would imagine that he would have caught it here."