Still confusion over BSE and CJD links

Background

What is BSE and what does it do?

It's an untreatable brain disease that kills cows, up to two years after symptoms start.

Bovine spongiform encephalopathy attacks the central nervous system, turning the cow's brain to sponge (hence the name). It has an incubation period (i.e. the time between catching the disease and showing symptoms) of between two and eight years.

It can only be diagnosed once the animal is dead. Scientists are hoping to develop a live animal test which would enable meat to be labelled "BSE free". Sick cows become nervous or aggressive. They stand bow legged, lose coordination and weight. Milk yields may go down and, invariably, the animal dies.

Dubbed mad cow disease, it is part of a family, called transmissible spongiform encephalopathies (TSEs), which affects other animals like sheep, goats, cats, mules, hamsters, mice, elks and minks.

How is it caused?

By animals being fed on other dead animals. It spread from sheep to cattle in Britain, where scrapie, the sheep form of BSE, has been endemic for centuries. Sheep remains were used as a protein supplement and are thought to have infected the British herd in the 1980s. Remains from infected cattle were also used in food, increasing the infection rate.

Although BSE has hit a number of countries, the scale of the epidemic has been highest in Britain, where the supplement was widely used and prepared without chemical solvents. Infection in other countries is believe to have come from exported British animals and animal food.

Is it a virus?

Not exactly. Scientists believe protein particles, called prions, are responsible for TSEs like scrapie and mad cow disease. The killer protein acts like a virus, but doesn't have any DNA. It has been found in infected animals. Not much is known about how it works and even less about how to stop it.

The theory is that it mutates other harmless prions in the body by changing shape. It is a highly resilient bug that can withstand temperatures and chemicals that would normally kill infectious agents. One report said the infection survived at 360C for one hour and burial in soil for three years, although others say that prolonged high temperatures will destroy it.

There are a lot of grey areas around this grey matter disease.

Nobody knows for sure the prion is the culprit. Some experts believe it may be linked to the use of pesticides as organic farms are less affected.

So if sheep are the source of BSE in cattle is it safe to eat lamb or mutton?

Unlike BSE, sheep scrapie has been around for a long time, with no evidence of transmission to humans. Scrapie has never been present on the same scale as the BSE epidemic in Britain. In France, where sheep's brains are commonly eaten, tests have shown no increase in cases of the human form of BSE.

When was it discovered and by whom?

BSE is 10 years old this year. It was first identified in Britain's Central Veterinary Laboratory in November, 1986, by a team of vets studying the carcass of an infected cow. The vet responsible has never been named. The first case of BSE notified on an Irish farm was in January, 1989.

Can humans catch it?

As recently as last December the experts said No. Now they're saying Maybe. They need more evidence to say Yes, but they are worried. Ten days ago a British advisory group said they had found a "previously unrecognised and consistent disease pattern.

Ten people aged between 18 and 41 have been diagnosed in the UK over a two year period with the human form of BSE, called Creutzfeldt Jakob disease (CJD). They appeared to have a variant of the "normal" CJD, and eight of them have died.

The disease usually affects people over 50, with an average incidence worldwide of around one death per million. The most likely explanation for the 10 deaths, the group said, was a link with BSE.

So when will we know the real risk?

There may be some answers next Wednesday after the results of a two day World Health Organisation conference in Geneva. The WHO admits it has been "caught unawares like the rest of the world" by the scare and will spend the two days trying to come to some kind of consensus on evidence of a link.

Some experts speculate that the British government must have been very convinced by the scientists to make the statement public before final evidence is available.

The next step towards an answer is to inject tissue from "normal" CJD sufferers into mice and compare the pathology with mice injected with the tissue from the 10 unusual CJD victims. BSE is a disease whose pathology does not change when it crosses the species barrier. So if the 10 unusual CJD cases show a different pathology the scientists will know there is a new, and probably BSE

related, strain. However, the experiments will take a while as it has an incubation period of six months or more.

Who was Creutzfeldt Jakob?

Two people actually. They were turn of the century German psychiatrists Hans Gerhard Creutzfeldt and Alfons Maria Jakob, who diagnosed the disease in a 22 year old woman in 1920 and four older patients the following year.

Creutzfeldt lived until the age of 85, while Jakob died in 1931 at the age of 47. Last week Creutzfeldt's grandson, Benjamin, said one benefit of the scare was that, for the first time in his life, everyone could spell his name.

How many people have died from CJD?

Forty people in Britain last year, which is about one death per million per year. This is the global average for the disease. In Ireland, 19 people died in the 15 years from 1980 to 1995. Fourteen of those were aged over 50, the age when the disease is more common. The remaining five were under 50.

The CJD surveillance unit in Edinburgh has recorded the death rate across professions. Abattoir workers, who might be expected to fall into a high risk category, have a lower than average rate of 0.2 per million. Farmers have a rate of five per million, but vicars and long distance lorry drivers have a higher mortality rate than farmers. As one expert put it, this highlights the futility of mortality statistics when the incidence is so low.

CJD is easily confused with Alzheimer's disease or a stroke, and can only be identified through a post mortem. There is also thought to be a genetic link where some people inherit a predisposition to the disease.

How widespread is BSE?

Much more in the UK than anywhere else. It has logged more than 400 times as many cases as all other affected countries put together. Since 1986, 158,882 head of cattle in more than 32,000 herds have been diagnosed with BSE in Britain. In Northern Ireland, there have been 1,680 cases, and the addition of Guernsey, the Isle of Man, Jersey and Alderney brings the UK total to 161,663.

There have been 124 notified cases of BSE in Ireland. The number in the UK peaked in 1992, when there were more than 1,100 a week. Now there are around 300 new cases a week.

The rest of the world (including Ireland) has had a total of 384 cases, with 205 in Switzerland, 31 in Portugal, 13 in France, 4 in Germany, 2 in Italy, 2 in Oman, 1 each in Canada, Denmark and the Falklands.

What were the measures taken in Britain and Europe to combat it?

A month after BSE was identified British scientists concluded that the source was animal remains used in cattle feed. Eighteen months later BSE was made a notifiable disease and the British authorities introduced measures for removing suspected BSE cattle, when calving.

On July 18th, 1988, the British government temporarily banned the feeding of dead ruminants (sheep, goats, cattle or deer) to ruminants. This was later made permanent. A compensation policy for the slaughter of infected animals followed. Milk from suspect animals was banned for anything other than feeding the cow's own calf.

Then the UK government started trying to take dangerous animal parts out of the food chain. In November 1989, two years after BSE was identified, it banned the use of brain, spinal cord, tonsil, thymus, spleen and intestine of cattle in foods for human consumption.

The EU banned the export from the UK of cattle born before July 1988. In 1990 the European Commission made BSE a notifiable disease, and the offal ban was extended to Europe and third countries. A British lab recorded transmission of BSE to a pig and offals were banned in the UK in all animal foods, including pet foods.

Farmers were required to keep breeding records, and at the end of 1991 meat and bone meal was prohibited from use in fertilisers.

In 1992 the EC banned the trade in bovine embryos from BSE suspected cattle born after July 1988.

In 1994 it banned the feeding of protein from animals to ruminants throughout the EU. The offal ban on human foods was extended in the UK to calves under six months of age slaughtered for human consumption.

Last year the British authorities demanded the heads of animals be removed and disposed of intact, without removing the brain or eyes, and spinal cords should not be removed, except in a slaughterhouse.

What action was taken here?

In 1990 the movement of cattle was controlled and the Irish Department of Agriculture banned the use of meat and bone meal in feed for cattle, sheep, goats and deer.

The importation to Ireland of cattle from Britain and animals from Northern Ireland was banned. The ban excluded calves if they were slaughtered before the age of six months.

Meat and bone meal was still permitted in food for pigs and poultry. Later that year the Irish Department of Agriculture decided to slaughter all animals in a herd where BSE is found.

In Britain only infected animals were being slaughtered. By December 1990 more than 2,600 cattle from herds with BSE had been killed in Ireland. The meat was deboned and sold to Europe.

By the middle of 1991 that figure had almost doubled and trade resumed with Egypt. Two years later Iran said it would accept imports of Irish beef after a three year ban.

By last December 15,000 animals had been slaughtered at a cost of more than £10 million. In January new tests on animals taken from BSE herds were introduced, subjecting them to microscopic examination before the meat was sold.

Two days ago Ivan Yates signed into Irish law an EU wide ban on British beef and all derived products, including gelatine.

So why hasn't BSE (or BSEphobia) gone away?

A number of farmers and a woman who worked in a butcher's shop died from CJD at the end of last year in the UK, sparking new fears about the risk to humans. Two British local government authorities banned beef from their menus and a number of senior scientists said they had stopped eating beef.

An Irish vet and member of the Consumers Council, Mr Peter Dargan, said animals slaughtered from herds with BSE cases should be destroyed rather than entering the food chain.

Last December London scientists published results from experiments which, they said, showed BSE could not be passed to humans. That was turned on its head 10 days ago when the British government's advisory group said there was a possibility of a link, or a new strain of CJD linked to BSE.

What about infections through blood transfusion?

There is no evidence that it can be transmitted through blood or blood products. The British Blood Transfusion Board has been excluding CJD sufferers from donor lists for a number of years. The disease would be very difficult to transmit via blood as prions (the suspected infective agents) are found not in blood, but in tissue.

Is mad cow disease going to go away?

The rate of BSE infection in Britain has climbed almost vertically from 1990, peaked and has now dropped from almost 1,200 cases a week to around 250. The apocalyptic vision, according to a British microbiologist, is that 30 million people will have consumed BSE infected meat by the year 2001. The alternative or best case scenario was that there was no risk at all, he said.

An Irish BSE researcher in UCD, Dr Mark Rogers, believes BSE will disappear of its own accord if the infection rate continues to spiral downwards at its recent rate of halving every year. The damage has been done in terms of infected meat and cattle food getting into the animal and humane food chain.

Even if 30 million people eat the infected meat there is no guarantee they will be infected. The amount you would need to eat is large. You need a lot of infection to cross the species barrier, and infection through the stomach lining is one of the most difficult ways to spread a disease.