Professor Pennington: Food may need irradiation

"We're beginning to pick it up in domestic animals, and of course the worry is how much of a risk this is to humans.

"Domestic animals are very likely to pick up 0157 from the environment. And equally, as it comes out the other end in their droppings, they will be passing it on.

"So anything that's attractive to children, like the tail of a dog, is potentially a source of 0157 for them. I don't know why we've had no cases linked with it. I suspect it could be just a matter of time before the link is proven."

Lanarkshire outbreak

E. coli 0157 first appeared in the UK about 20 years ago, though it was not until the 1996 Lanarkshire outbreak that it attracted widespread attention.

Professor Hugh Pennington of Aberdeen University is one of the UK's leading experts on the bacterium.

He told Costing the Earth it has the ability to mutate: "There are lots of variants circulating now.

"Those must have arisen by variation occurring since it got here. So it's really quite a versatile bug.

"It may even mutate faster than some ordinary bugs. There's some evidence for that."

Detection systems

Another contributor to the programme is Dr Norman Simmonds, a member of the government's advisory committee on the microbiological safety of food.

Farms can be risky

Dr Simmonds said other strains of E. coli, for example 0111 which has often caused illness in Australia, could arrive in the UK.

"At any time they could pop up, and that would be very serious, because most of our detection systems are directed against 0157.

"It won't be so easy to pick the others up. It's possible, but it's much more expensive.

"Worse than that, it's slower - and that's bad news if they do spread. And they may do.

"You can go to any big supermarket counter and find food from 30 countries around the world.

"It's not all sterile, it's vegetables and meat, and there are bacteria there. So there's plenty of opportunity for organisms to spread round the world.

Other bacteria

"And there's the possibility that the capability of producing toxin might spread right out of E. coli into other species of bacteria.

"Then we'll get the same disease from something else, as happened in Germany a little while ago."

Professor Pennington said it might become necessary to combat 0157 by treating food with radiation.

"It could be made to work. It's a well-understood technique, and it's quite safe.

"The problem is persuading the public that it's quite safe, and at the moment everybody thinks that's an impossible task."

Costing the Earth, presented by Alex Kirby, is broadcast at 2100 BST every Thursday on BBC Radio 4 until 1 June 2000