What is the real cause of BSE?

What is the real cause of BSE?

By Bill Lavers

(Article from the NRA Bulletin, April-June 2000, Issue No. 826)

The greatest difficulty facing scientists as they search for the cause of BSE and vCJD is the ubiquitous misunderstanding and misinformation that has been circulating about these diseases. How they are caused and how they are linked; the fundamental truths - or the pathway that leads to them have been buried in a miasma of falsehoods.

Dr David Brown, senior fellow at the Department of biochemistry at Cambridge University, recently made his views on the subject publicly known in an article in Chemistry & Industry magazine in February. The truth about how little is known, he says, has been covered up by theories presented to the public as facts; and in fact so little is known for certain after all this time precisely because the popular theories have been taken for truth by the politicians and rule-makers within the European Union.

In our Jan-Mar Bulletin (No 825) we published a News report about this article, which goes against the grain of popular thinking on BSE/vCJD. We recently spoke to Dr Brown, to get a better insight into BSE and the TSE related issues he has raised. Dr Brown has been studying transmissible spongiform encephalopathies (TSEs) and prion diseases since 1995, and he has some compelling, if unconventional, views on the subject.

In particular, he has described much of the “conventional wisdom” on BSE/CJD as “staggering falsehoods,” and identified the three key falsehoods as being that:

• BSE was caused by transmission of the sheep disease scrapie to cattle
• vCJD is caused by eating beef (from BSE-infected animals)
• all current BSE is caused by BSE-infected rendered animal material.

Seemingly, these popular hypotheses have grown out of the political statements made to the UK parliament back in March 1996, to the effect that BSE was the most probable cause of the cases of vCJD then coming to light. But the balance of probabilities in 1996 - has since been taken as certainty by almost everyone concerned at every level.

As Dr Brown points out, despite the fact that BSE has been appearing “sporadically”in several European countries over a number of years, the current view of the European Commission is that all BSE originated from the UK. “Such an idea,” he says, “is absurd.”

General causes of TSEs

Historically, sporadic forms of TSEs are the most common, accounting for 85% of cases. They arise in older animals when something goes wrong with their brains. Dr Brown says that in most cases there is no known cause, although there are certain places where the disease is more common than others. There is no “infection”, it just happens and environmental factors are as likely a cause as any other.

Normally, BSE appears in older cattle (the first case in the UK was 18 years old) and CJD occurs in older people, if they survive other causes of death long enough to exhibit outward symptoms.

The link between BSE and vCJD

There is no direct scientific evidence that BSE and vCJD are linked through eating.

For the specific notion that vCJD is “ contracted” in humans by eating beef and beef products from cattle infected with the BSE agent, Dr Brown points out that all the evidence is circumstantial. While this remains the case, Dr Brown says we must consider other possibilities. After all, by all accounts there have been millions of tonnes of BSE-infected beef in the UK food chain, and the number cases of vCJD remains small (around 100). In France, by contrast, the number of BSE cases very much smaller, but already there have been 4 confirmed cases of vCJD. Put another way, the BSE/vCJD ratio in France less than 60, while in the UK is in the order of 3000. There must be other explanations.

While the chances of a feed link from one species to another remain remote, Dr Brown confirms that there is likely to be feed link within a single species; for example, when healthy cattle were being fed MBM derived from BSE-infected cattle. Dr Brown points out the similarity with the human disease Kuru, which was propagated among cannibalistic tribes through eating the brains of their infected victims. But this does not explain where BSE came from in the first place and it does not explain how BSE has become so widespread in the EU now.

Dr Brown dismisses the notion that all cases have emanated from illegal trade feeds/MBM laden with viable BSE agent.

In fact, it is quite possible that BSE in cattle and vCJD in humans are only linked through a common cause or similar cause, and that both are likely to be novel sporadic prion diseases, but which are also now capable of affecting young people and young animals. Dr Brown sees these new prion diseases as a totally novel, possibly “post industrial” phenomenon. Why are young people and young animals getting it?

“Something new is happening,” says Dr Brown.

Through the placenta?

Transmission through the placenta is one explanation or the fact that calves and young people have developed BSE and vCJD - Dr Brown believes this is “quite likely within a species”. Dr Brown says that there are three possibilities, but that it would be difficult (with humans impossible) to under-take experiments to prove them.

1. Increased susceptibility very early in life
2. An asymptomatic mother (carrying the disease at non-clinical/sub-clinical level) can pass it across the placenta to an un-born child.
3. (the least likely) An uninfected mother (with a resistant genotype) can eat infected meat and pass to an unborn off-spring (with a susceptible genotype).

What is the most likely explanation? The main driver for development of these TSEs in young people/ young animals? “Exposure to something in the environment that certain young people/animals are susceptible to,” says Dr Brown. But what could it be?

Link with metals

One possible “something in the environment” is metals. Dr Brown has been investigating the link between prions and metals for some six years, as part of his bio-chemical work to develop an understanding of the functions of prion proteins.

Prions proteins are present in normal brains, and Dr Brown has been investigating what they do. In fact, they bind copper, and a lot of proteins that bind copper are antioxidants. Their function is to breakdown “superoxide”, the precursor to the “reactive oxygen species” that would cause damage if they were not eliminated. The enzymes that break down superoxide are superoxide dismutases, and normal prion protein is one of these.

The development of abnormal prion proteins is a central factor to all TSEs; and Dr Brown says that all TSE’ s show a lot of oxidative damage.

The holes (spongy texture) in TSE brains, and how they are formed, is connected to the way the neurons die.

Preliminary evidence shows that some groups of CJD patients have ten times the normal levels of manganese in their brains, which leads Dr Brown to suggest that high levels of manganese in the environment may increase the risk - or the susceptibility - of CJD. Indeed, high manganese levels in the brain could be a specific hallmark for TSEs; and in Dr Brown’ s view, the imbalance of metals (Cu/Mn) in the brain “might lead to the formation of abnormal prion proteins.” At any rate, the imbalance of metal ions in the brain are clearly linked to prion diseases in some way.

One possibility is that animals are often fed high Mn diets to boost their fertility, and this practice could have initiated prion disease. But Dr Brown’ s preferred suggestion is that these new prion diseases may be a consequence of industrial activity - mining and metallurgical processes - over the past hundred years or so.

In this way, he concludes that countries in which animal husbandry is, or has been, closely juxtaposed with industrial activity will exhibit these new TSEs the most. It is possible he says, that countries like Australia and Canada, where industrialization is low in relation to their size - or where mineral industry, populations and livestock rearing are not close neighbors - may never see them.

On the basis of his own biochemical evidence and the data he has collected, Dr Brown is calling for a new look at the causes of BSE and vCJD. “A lot of these issues are ignored now,” he says, because the hypothetical link between BSE and vCJD through eating has been accepted as fact at the political level.

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