New evidence has claimed cattle can be infected for BSE for years without showing any signs. David Edward looks at whether a BSE timebomb is waiting to go off.

Vet David Bee was first called to Pitsham Farm three days before Christmas 1984 after a call from its worried owner.

It was a farm much like any other in Sussex, located less than a mile from Midhurst.

Nobody could have known the farm, tucked away on a quiet lane off the A286, harboured a terrible secret.

Farmer Peter Stent had called the vet because his cattle were suffering from a variety of unusual ailments. One had an arched back, had lost weight, was uncoordinated and had a trembling head.

At first it was thought the animal had a kidney infection, for which it was unsuccessfully treated. It died the following February.

In January, Mr Bee and his partner noticed a second cow at the farm was behaving strangely.

In a later report to the BSE inquiry, he said: "Mike Teale and I examined a 'downer' cow.

"We both noted how aggressive she was. Mike in particular told of her 'chasing him across the box on her knees'."

By the end of April, six cows at Pitsham Farm had died and Mr Bee was still at a loss as to why. Mercury poisoning, toxins from a small brickworks on the farm and malicious poisoning were all suspected but each theory turned out to be incorrect.

By September, Mr Stent's herd of eight cattle had been reduced to just one animal.

In a last-ditch attempt to get to the root of the problem, the animal was put down and parts of its body sent to medical experts who discovered it had bovine spongiform encephalopathy, or BSE.

Although the illness may have started in cows in the early Seventies in levels undetectable to vets, the cases at Pitsham Farm were the first recorded.

Giving evidence to the BSE inquiry set up in 1998, Mr Bee recalled his disbelief at the findings, but nothing could have prepared him, or the British public as a whole, for the outbreak which was to follow.

It is now thought that allowing cows to eat the remains of other cattle and sheep in their feed led to the crisis which infected 177,000 cattle in Britain and led to the deaths of 70 people in the UK from new-variant Creutzfeldt Jakob disease (CJD).

There is no suggestion that the disease began at Pitsham Farm as separate incidents were later recorded around Ashford, Kent, and it could have affected herds across the UK.

One of CJD's victims was Graham Byrne, a 39-year-old father of three who died of the hereditary form in February last year.

Mr Byrne, of Southwick, was a happy family man who worked as a cabinet maker and had been an active sportsman before he began to suffer from the disease in 1993.

At first his wife, Maria, thought he was depressed as a result of being made redundant.

After his death, Mrs Byrne said: "He started getting more and more forgetful, a bit like people who have Alzheimer's, though he was far too young for that.

"We realised something major was wrong when one of the children, who had started at nursery, came home and asked him to make a rabbit hutch.

"Graham was a professional carpenter but he tried to drive a 6in nail into a 1in thick piece of wood and he just didn't know how to do it.

"From then onwards, things just went from bad to worse.

"In the end he had to be washed and dressed and he couldn't communicate anymore. I could see at first hand how the agony and pain these people go through is terrible."

Until this week, farmers, politicians, the public and most of the scientific community believed the crisis was effectively over.

Stringent measures such as the slaughter of cows over 30 months old under Government compensation schemes and bans on beef on the bone were meant to reassure people that British beef was safe to eat.

By the late Nineties things seemed to be returning to normal.

In 1997 McDonald's started using British beef in its burgers after a 15-month ban and the following year the European Union lifted its export ban.

Mr Stent, speaking from his farm yesterday, said: "I just wish it would all die and go away. It has just devastated so many people's lives.

"It has had such a devastating effect that the sooner it is forgotten the better.

"But the BSE thing is declining at such a rapid rate that soon there won't even be a case in the country." Unfortunately for the farming world and the British public as a whole, the new evidence suggests the BSE crisis could be far from over.

It suggests cattle can harbour the disease without showing outward signs - random tests conducted last year on 3,000 cows showed 18 such cases.

In a worst-case scenario, scientists predicted 136,000 people could become infected with CJD and its variants.

A spokeswoman for the National Farmers' Union said: "Farmers are not scientists so it's difficult to comment on the validity of this research. Neither have we seen the report.

"It is important to note that Professor Hugh Pennington of Aberdeen University has said that the research is nothing new and does not produce evidence of a threat to public health."

The Government now plans to begin surveys on a further 3,000 animals which die unexpectedly on farms or have to be slaughtered through illness.

However, some in the scientific community fear it may already be too late for tens of thousands of people.