Should we still be worried about BSE?

UK - When the news first broke that 'mad cow disease' could be passed to people, some scientists predicted that tens of thousands of us could eventually die of vCJD, the human form of BSE.
calendar icon 22 January 2007
clock icon 5 minute read

Ten years on, the death toll stands at 160. So has the real danger passed? Or are many of us still carrying the disease unknowingly? Ian Sample talks to the scientists most closely involved in the crisis and learns that the real threat now is not from cows - but from other humans.

There was a long night ahead. A group of scientists, each expert in the minutiae of disease, had been summoned to an emergency meeting in London. Some caught planes and trains back from a conference on the European continent to be there, others dropped their routine work at some of the finest institutes in the country.

What had begun as a farming problem was about to erupt into a far-reaching crisis. At 10 the following morning, having worked through the night, those assembled released a note to the prime minister outlining what many had long been sure of. That in direct contradiction of the government's 10-year campaign of reassurance, an infection that had caused rapid and fatal brain disease in nearly 200,000 cattle posed a grave threat to human health. Ten young people had been identified as suffering from what was to become known as variant Creutzfeldt-Jakob disease (vCJD), a deadly, human form of bovine spongiform encephalopathy (BSE). Some, it became clear, had already succumbed.

The announcement of the news, on March 20 1996, fell to Tory health secretary Stephen Dorrell and caused more than a slashing of beef prices at supermarkets. Many were furious about the Conservative government's handling of the dangers of eating BSE-contaminated meat. They had heard the chief medical officer, Sir Donald Acheson, declare categorically that beef was safe for everyone to eat, a message repeated by his successor. They had seen John Gummer, then agriculture minister, feed his four-year-old daughter, Cordelia, a beefburger in front of cameras in Ipswich. Confidence in the government, and to a lesser extent the scientists it consulted, evaporated.

In the absence of hard facts, speculation over the eventual human death toll reached apocalyptic proportions. The doom-laden predictions now look to be well off the mark, but has the threat really passed? More than 10 years since Dorrell's announcement, and 20 years since the first cases of BSE were identified, at least 160 people have died from vCJD and more are expected to die soon.

But despite billions spent on efforts to save Britain's beef industry and protect its citizens, all the major questions remain unanswered. The origin of the disease? A mystery. The number of people infected with vCJD? A mystery. The risk that those harbouring the disease will infect others? Again, a mystery. And since there is still no blood test and no cure, the final death toll is anyone's guess. Right now, the only sure-fire test for the disease involves examining chunks of people's brains or other internal organs, and so is usually only performed on the dead.

The story of BSE in Britain is a case study in the ruthless efficiency of intensive farming, the self-serving behaviour of government departments and the patronising caution extended to the public when explaining risk. It reveals the impotence of the scientists involved - at least at the outset, when they were being called upon to give meaningful advice while still battling to understand a disease they had never encountered before.

At the end of 1986, pathologists at the Central Veterinary Laboratory were analysing slivers of brain tissue sliced from cattle that appeared to have contracted a new disease. It left the cattle uncoordinated and jerky, and ultimately proved fatal. Under a microscope, the brain damage resembled scrapie, a disease caused by rogue proteins known as "prions" that had been endemic in the national sheep flock for nearly 200 years.

Without publicity, an investigation was launched to find the cause of the outbreak. It revealed an alarmingly widespread disease. One year later, 95 cases of BSE had been confirmed on 80 farms. By February 1988, 264 cases had been tracked back to 223 farms. The number of cases began to grow exponentially.

"It was turning into a major crisis and there was all sorts of wild guesswork going on because no one understood it," says Chris Higgins, who now chairs the government's advisory committee on spongiform encephalopathy diseases. "The politicians didn't know what to do and the scientists didn't know what to do. We didn't know where it came from, what caused it, how bad it might be. We didn't know anything."

John Wilesmith, an epidemiologist and lead investigator at the Central Veterinary Laboratory, suspected that cattle feed - the common factor linking the cases - was to blame. Specifically, he proposed that scrapie-infected sheep offal had been mixed into meat-and-bone meal, a nutritious food source that is made by grinding down and baking a slurry of sheep and cow remains. The process had been perfected by the rendering industry (which uses every scrap of the animal carcass for various products) during an efficiency drive in the aftermath of the second world war.

The investigation led to the government imposing what the cattle industry regarded, at the time, as a draconian measure - a ban on the use of certain meat-and-bone meal in feed for cattle and sheep. The ban was followed by compulsory orders to slaughter all animals showing signs of BSE. The moves were made to protect cattle, but the possibility of risk to the public had not gone unnoticed.

As events gathered pace, Acheson, the chief medical officer, set up a working party, headed by Sir Richard Southwood, an Oxford University zoologist, to advise on the implications of BSE. When the working party reported back in early 1989, it agreed that scrapie-contaminated meat and bone meal was the most likely cause of the BSE outbreak. It advised that baby-food manufacturers should stop using cow and sheep offal, especially the thymus (a gland known to be highly infected by scrapie prions), in their meat-based meals. But it still maintained that it was "most unlikely BSE would have any implications for human health".

Source: The Guardian

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