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Cattle on the brain

by Emma Young*

* New Scientist

For years it was called “the British disease.” But BSE, which kills cattle and causes a fatal brain disorder in people, has spread through much of Europe - and panic has spread with it. To date, nine European countries have reported infected cattle. Between 1999 and 2000, cases of the disease doubled in France, and reports that beef from infected herds was on sale on supermarket shelves shocked the nation.

Rex Features/Peter Trevnor

Last year, Germany, which had long proclaimed itself to be BSE-free, was also forced to admit that its herds had been infected, triggering widespread public alarm and anger. “They made fools of us with the long-winded promises that Germany is safe from BSE,” said the Berliner Morgenpost.

There are also fears that BSE outbreaks could emerge outside Europe. Last December, a South African woman who had never been to Europe died from the human form of BSE. The announcement came amid allegations that Britain had put potentially contaminated animal feed on world markets, while it was banned in the UK.

The UK is still home to around 90% of all “mad cows” - but the number of new cases is on the decline, while in many other European countries, it is rising. Denmark, Portugal, Spain, Belgium, Switzerland, and the Netherlands, as well as France and Germany, have all reported cases of cattle infected with BSE. And many experts think that new EU rules enforcing widespread testing of all cattle over 30 months will reveal cases in other countries that are currently denying any infection.

New EU laws

The new EU laws on testing are part of a tough new set of anti-BSE measures announced last November. BSE is thought to be primarily transmitted through eating infected animal remains. The feeding of all livestock with products containing meat and bonemeal has now been banned. And all cattle over 30 months old (thought to be the age at which they can become infectious) must now be slaughtered if they do not test negative for BSE.

These procedures are already in force in the UK, where more than 4.6 million cows over 30 months have been killed. But the new measures have divided Europe, provoking anger in countries that claim their own safeguards are already sufficient.

EU ministers hope the measures will stem the spread of the disease and eliminate the risk to humans. But no one knows how many people have already been infected, or how long the incubation period might be. Estimates for the future death toll from vCJD - variant Creuzfeld Jacob Disease, the human form of BSE - vary from hundreds to hundreds of thousands.

How do you get it?

Although the first cases of vCJD are thought to have been caused by eating infected beef, there are fears that the disease could be transmitted in transfusions of infected blood, or even during tonsillectomies. John Collinge, a British BSE expert at Imperial College in London, controversially estimates that half the surgical kits used to remove tonsils in the UK could be contaminated with vCJD.

Collinge predicts that a vCJD epidemic in Britain - and perhaps in other European countries - might now be waiting in the wings.

Some of his most recent research suggests that a person’s genes might determine how rapidly they develop symptoms after infection. All the 84 people diagnosed with vCJD to date have or had a particular genetic make up, which is found in around 40% of the population. But Collinge suspects that, far from being safe, the other 60% simply incubate the infection for longer.

“We’re saying there might be lifelong incubation periods,” he says.

The infectious agent in both BSE and CJD is a misshapen form of a prion, a protein found mainly in the brain and central nervous system. The abnormal prions accumulate in clumps in the brain, but it is thought that their interaction with other molecules, rather than their clumping, causes the devastating effects.

The first case of bovine spongiform encephalopathy emerged in a Sussex farm in 1984. A vet was summoned to inspect a cow with head tremors and an arching back. Six weeks later, the cow was dead. Seven months later, the UK Central Veterinary Laboratory made its official diagnosis.

British ministers were informed about the emergence of BSE in 1987, after cows from four herds had been diagnosed with the disease. One year later, the government established a group of scientists to investigate. For years they found little evidence that BSE could cross from cattle to infect another species, and the British government repeatedly told the public that eating beef was safe.

But in 1995, the first cases of vCJD were diagnosed in humans, and in March 1996, after eight human cases had been recorded, the British Parliament was told that the most likely cause was eating beef products contaminated with BSE.

First Britain...

In the UK, the BSE fiasco was the subject of a major investigation, which culminated in a report published late last year. Ministers were criticised, but escaped severe blame. According to the investigating committee, there was no way the British BSE epidemic could have been prevented, because by the time the first case had been diagnosed, thousands of cattle had already been infected and were incubating the disease,

However, many analysts think Britain could have done more to contain the outbreak.

In the early years of BSE, farmers were paid only 50% compensation for infected cattle. Critics say this probably led to infected carcasses being illegally sold - and this furthered the spread of the disease.

They also say that the British government should have acted faster and more effectively, particularly in banning feed containing meat and bonemeal. For years, scientists advised that potentially infective tissue from slaughtered cows, such as the spinal cord, should not be recycled into animal feed - but the practice remained widespread.

Critics also say Britain should have halted the consumption of cattle above the infectious age limit sooner - and moved earlier to prevent beef exports. Although the EU banned all exports of British beef in 1996, thousands of potentially infected cattle had already been shipped to Europe. Germany received some 13,000 cattle from the UK between 1980 and 1993, and France imported many more.

...now Europe

Now herds in much of Europe are thought to be infected, and the cost of the clean-up will run into many millions of euros. The EU has agreed to pay 70% of the costs. But governments of some countries that claim they have already implemented effective BSE safeguards say the cost is unfair.

Finland argued that the measures are “unjustified” in its case. And the Dutch, in particular, are unhappy about the ban on feed containing meat and bonemeal. But although they argue that it will be tough to find an alternative high-protein feed for their millions of pigs, most BSE analysts argue that the ban, along with EU-wide blanket testing and slaughter, is essential if the widespread denial, finally followed by embarrassed admission, in Germany is not to be repeated.

However, the testing many not end with beef. Some British experts are even calling for a mass screening programme to establish whether BSE could have spread from cattle to sheep.

Mad sheep?

“Of the 40 million sheep in Britain, some 4,000 succumb annually to another disease, scrapie, which appears not to have any human health risk. It is possible, however, that some of these animals are actually suffering from BSE,” says Sir John Krebs, chair of the UK’s Food Standards Agency.

“We simply do not know whether sheep are also dying from BSE,” he said. Or whether eating lamb could also pose a health risk to humans.

The lack of knowledge has prompted massive increases in research into BSE and prion diseases in Europe.

Last November, French Prime Minister Lionel Jospin announced that his country would treble its spending on basic prion research to FF210 million for 2001. Germany has also announced huge research spending increases.

Hopes of a test and a cure

At present, there is no cure for BSE or for vCJD. However, in December 2000, a Swiss team did announce a major breakthrough, which is raising hopes of a fast, accurate test for the disease in living people, and even a potential treatment.

The team identified the first natural molecule that binds strongly to abnormal prions, but not to normal ones. The molecule is called plasminogen, an inactive form of a chemical thought to be essential for thought and memory.

Sipa press/H. Lane

The discovery could also mean donated blood could be effectively screened for the rogue prions. Almost a dozen countries have already banned blood donations from people who have spent more than six months in Britain. Experts think that any infectious prions in blood would be contained in the white blood cells, and the majority of these cells are routinely removed from blood in the UK. But some critics have claimed no one can be sure the infectious agent cannot be carried in other parts of the blood. The fact that plasminogen binds to the deformed prions makes this much more likely. But it also raises the hope that plasminogen could possibly be used to mop up the prions in infected animals or people.

If John Collinge is right, unless more urgent prion research is carried out, the human cost of the BSE tragedy may end up being much higher than the cost to Europe’s farmers.