Guinea pigs and hamsters are being tested to see if they passed on the E. coli bug to children at Godstone Farm in Surrey.

The animals, as well as some rabbits, were the only animals that children were allowed to touch after health enforcement officers ordered that all contact with larger, high-risk animals end on September 3.

Health chiefs have now accepted that they may have wrongly advised the farm to close the touching barns — which house cattle, goats, sheep and pigs — but to allow contact with smaller animals to continue.

The admission by the Health Protection Agency (HPA) followed a welter of complaints from parents demanding to know why the farm was not closed immediately once it had been linked with cases of illness.Graham Bickler, the regional director for the HPA in the South East, conceded yesterday: “It possibly turns out to be the wrong advice but it was what we knew at the time based on previous evidence and previous experience.”

There were no new reported cases last night but experts are expecting more cases in the coming days.Three children were still in a serious condition and a further nine, all under ten, are being treated in hospital for complications including kidney failure.

Two-year-old twin boys, Aaron and Todd Furnell, were said to be “stable” on kidney dialysis machines at St Thomas’ Hospital in London after visiting the farm on August 31, four days after the first case was reported. Their five-year-old sister, Jodie, has also been “very ill” and treated in hospital in Kent.

Tracy Mock, their mother, demanded to know why the farm was allowed to stay open. “I heard that cases were reported there on August 27, yet we went there on August 31. Why wasn’t it shut down before then? If it had been, my two boys wouldn’t be in hospital on dialysis. If the public health authority didn’t think it should have been closed, Godstone Farm should have done it themselves.”

Health chiefs are now waiting to see how many cases emerge in the ten to fourteen-day incubation period, now that the farm has closed.

Dr Bickler said last night that when he had said “wrong” advice may have been given to the farm he did not mean it was “wrong” when given. He told The Times: “It is possible that new elements will emerge in this investigation that may alter the guidance for dealing with future outbreaks.”

He said that the evidence and experience-based risk management advice showed that the high-risk areas on the farms were the barns where children could get close to large animals.

“I can understand why parents have said we should have closed the farm immediately but we could not do that on the basis of what we knew.”

Paul Barton, the head of environmental health services at Tandridge District Council, who, along with the HPA, decided that the farm should close, said lessons would be learnt at Godstone Farm for every other petting farm in the country. He said: “We thought we would follow the practice of previous outbreaks, which showed cases were linked to large ruminant animals in pens. By closing the petting barns we did not believe there would be any new cases. Then on Friday we learnt of someone who had visited the day after the barns were closed.”

This has prompted the testing of the guinea pigs, hamsters and rabbits. Children were also able to pat the back of Shetland ponies and these animals are also being tested.

Checks on the water supply at the farm are also being carried out to ensure that there was no contamination from farm run-off into the mains supply. Samples are also being taken from the metallic picnic tables, playground equipment and fences where the E. coli O157 bacteria can survive for several months. Food has been largely ruled out of the investigation because most families brought picnics.

Jill Greenfield, a partner at the solicitors Field Fisher Waterhouse, who ten years ago represented a schoolboy who suffered permanent brain damage after contracting E. coli on a school trip to a similar petting farm, said: “I expect there will be litigation linked to this outbreak. It is the responsibility of the farmer, who had a duty of care, and the right course of action was to close the farm.” On Sunday, Richard Oatway, the farm manager, defended the response. “We were told in August [that there might have been an outbreak] and we have taken the decision to close the farm until the authorities have finished their investigations,” he said.

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