Up Close: Written in the Sands - was dog excrement the source of Heather's infection?

Close Up: Written in the Sands - due to be screened in the Midlands and the South West on BBC2 at 7.30pm on Thursday - investigates the death of Heather Preen.

The eight-year-old, from Rednall in Birmingham, died on 8 August this year - 12 days into a family holiday to Dawlish Warren in south Devon.

She had been infected with E.coli 0157 - a bacteria which has only been recognised for a decade, and about which very little is known.

However, it is known that it can only be contracted by ingesting infected excrement.

Heather Preen died 12 days into her holiday

There is no cure for the infection, which can cause haemolytic uremic syndrome - poisoning of the body's cells, which can result in kidney failure, brain damage and death.

Food was very quickly ruled out as the source of Heather's infection.

Nine further cases of poisoning soon came to the attention of the authorities, including Louise Edwards of Dudley, who suffered kidney failure.

These came from three families who had all been in the same area of Dawlish Warren beach on the same day.

The waters off the beach were tested for the E.coli strain after they were notified of Heather's case, but nothing was found.

Professor Hugh Pennington: "Dogs more than a theoretical source of infection"

Environmental health officers eventually concluded that the infection may have been brought to the beach by an animal, possibly a dog.

Barrie Trevena, and environmental health officer who has conducted a three year study into the infection, told programme makers that it was "highly likely" that a dog could have been a host for the bacteria.

He said: "It does seem that all of the children were in a very localised area on this beach.

"If there was some contamination of the sand by some dog excrement or maybe another child who'd had diarrhoea ... that excrement probably got onto the hands of the children."

Professor Hugh Pennington, an expert in E.coli 0157 who investigated Britain's worst outbreak in Scotland in 1996, said: "Dogs can pick up E.coli 0157 by coming into contact, for example, with cow pats.

An invisible amount of excrement is sufficient to cause infection

"They can carry it mechanically on their feet, or can become infected and excrete [infected faeces].

"Dogs are definitely more than a theoretical source of infection."

According to Dr Mark Taylor of Birmingham Children's Hospital, E.coli infections cause kidney damage in about 200 children a year in Britain. Of those, five or six die.

He said: "You've got a child who was well a few days ago, had what appeared to be a trivial illness and then they are acutely ill and needing very specialist treatment.

"The terrifying thing is to see is a child who has got this condition. They start to become irritable or vacant, or not know their parents, then very quickly they can have fits and they become comatosed. All this happens in just a few hours."

Programme makers say that while there is no conclusive proof that dog mess was the cause of the outbreak at Dawlish Warren, the possibility must prompt a review of whether dogs should be allowed in bathing areas on beaches.