Bovine Spongiform Encephalopathy is a degenerative brain disorder of cattle known more commonly as Mad Cow Disease. It is part of a family of diseases known as Transmissible Spongiform Encephalopathies, or TSE's. It was supposedly first discovered in November 1986 in the UK and by the following October, more than 169,472 cases had been identified. Other sporadic cases were soon identified in countries such as France, Portugal, Germany and Ireland. The occurrence of BSE in the United States or any other major milk producing country outside the European Union has not been officially confirmed.

BSE causes small holes to form in the tissue of the brain, giving it a sponge-like texture. Similar spongiform diseases such as CJD (Creutzfeldt-Jakob disease) have been identified in humans since the 1920s and scrapies has been existent in sheep for around 250 years. Cattle that are infected with BSE begin to show signs after around 5-10 years of life; so infected cattle may not be identified until the disease has already been passed on. In fact, depending on the life of the cattle, the disease may not be identified at all. It is believed that the build up of an abnormal protein called a prion is the cause of BSE, leaving holes in the brain causing serious neurological impairments and eventually death. BSE can only be diagnosed by inspecting the brain, hence BSE can only be diagnosed once the animal is dead.

Symptoms include apprehensiveness, nervousness, reluctance to cross concrete, turn corners, enter yards, go through doorways or permit milking, occasional aggression directed at other cattle or humans, manic kicking when milked, head shyness with head held low, high stepping gait particularly with hind legs, difficulties in rising, skin tremors, loss of weight or the ability to yield milk.

BSE is usually transferred from cow to cow via their feed, which used to be made from recycled parts of carcasses from infected cows. These parts of dead cows were fed back to cows as a protein supplement and thus passed on the disease. It was originally thought that BSE developed after scrapie infected sheep parts were included in the cattle feed and thus its spread was sped up by the consumption of recycled brain tissue from cows that had themselves become infected. However, Ministry of Agriculture researchers have not rejected the scrapie link claiming changes in the abattoir by-product treatment meant that processed tissue was no longer exposed to certain chemicals or high temperatures which killed the BSE prion. Scientists are yet to prove other forms of transmission including maternal transmission via milk, blood or amniotic fluid. Some scientists claim that there may be some degree of maternal transmission but there is also evidence that cattle can inherit a genetic susceptibility.

The central nervous system consists of the brain and spinal cord, both of which play a huge part in the receiving and directing of nerve signals around the body via the peripheral nervous system. When the brain is infected with BSE, its functions are severely impaired and thus the cow's behaviour is abnormal. Although BSE has no direct affect on the spinal cord, it is still infected and can still pass on the disease to another cow if consumed. A normal unaffected cow will have none of the symptoms of BSE, it will be able to co-ordinately walk around corners and through doors, stand up and down cross concrete and yield milk. Once the cow has been infected with BSE, even these simple functions become almost impossible for the cow or it seems reluctant to complete the task.

After the disease was discovered in 1986, tests were run to find the cause and method of transmission of the disease. After months of study, a hypothesis was announced that bone meal and meat in cow feed was the only plausible cause of BSE. Requests were sent out to several compounders asking for details on the cow feed including how much bone meal and meat was included etc. The results added plenty of back up for the hypothesis, and in 1988, BSE became an official disease with the transmission declared being via cow feed. As soon as BSE was known to be transmitted via cow carcasses in cow feed, a total ban was put on the feeding of recycled animal tissues to cattle and other animals. This was a large success and estimations were made that the disease would be eliminated by 1999, but these have been rethought due to the unsatisfactory handling of Specified Risk Materials (SRM), which are organs identified as possible carriers. Certain SRM's include the brain, spinal column, spleen, thymus, tonsils, and intestines.

Soon enough, humans became concerned that BSE could be transmitted to humans via beef products. Although several scientists claimed that there was no chance it could pass on to humans, people were still concerned. In late 1988, the beef consumption rate dropped slightly due to the BSE scare, but in 1990 it dropped by almost 30% due to a newspaper article on a cat which had caught a form of Feline Spongiform Encephalopathy. After only two weeks the consumption level had recovered to 95% that of what it was before the scare.

In 1995, the UK beef industry had another scare after newspaper reports linked BSE with the contraction of CJD and supermarket sales immediately dropped by 18%. In March 1996, BSE became a worldwide issue. This followed the UK Minister of Health announcing the discovery of a new strand of CJD, which became known as nvCJD (New Variant Creutzfeldt-Jakob disease). The announcement lead to the speculation that cows and their beef products could in fact infect humans with BSE. Only 7 days after that there was a total ban on the export of UK beef. On May 3 1996, a slaughter program began that would lay waste to any cow that was over 30 months old at the time. By December 1,643,057 retired beef and dairy breeding cows and 337,586 prime beef animals over 30 months old had been destroyed at an estimated cost of £1 billion, or roughly £1,000 a head. This project is expected to continue until all breeding animals born before August 1st 1996 are destroyed at the end of their working lives. By the end of 1997, around 12,000 beef breeding animals were being killed a week.

In the midst of all this, the UK was still trying to lift the ban on its beef. To show its co-operation, the UK culled a further 50,000 more adult cows which were identified as most likely to be carrying BSE and 14,000 more cows which were the offspring of BSE infected cows. They did this in return for permission to export beef from cattle born after August 1 1996, when the SRM became an illegal substance and there was no further risk of BSE being transmitted.

After the beef ban, consumption of beef rose to about 80% of normal levels, except for processed meat such as beef burgers which took a little longer to recover. These are the precautions that the UK and other infected countries have taken out to attempt to destroy the outbreak of BSE again. If everything continues on as it has been the past few years, they estimate that BSE will be extinct by 2005. Because of this, there aren't many future developments needed to aid in the destruction of BSE. Instead, scientists should start to look at nvCJD, even though only 1 in 1,000,000,000 people will catch it.

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The sick thing about all of this is that BSE and CJD have been known about since the mid 1940s.

A fairly comprehensive book on this topic, "Deadly Feasts" by Richard Rhodes was published maybe three years ago.

If documents the adventures of a couple English doctors who were doing research amoung some of the cannibals in New Guinea.

Many of the women developed a strange nuerological disorder, the symptoms of which are today known in the medical community as CJD, BSE, etc.

It turns out that amoung these cannibals, the highest honor one could bestow upon his or her family was to ask them to consume ones body after death.

These cultures were matriarcal, typically being led by the oldest (and probably wisest) woman alive.

To her went the highest of all honors - consuming the brain of the deceased. She could, at will, extend this honor by allowing other woman from her clan to eat some of this tissue as well.

The fact that they typically didn't consume their dead until they had been buried for several weeks didn't help things much either, I suspect.

The two doctors suspected the involvement of a new agent, something which took decades and many advances in technology to isolate, but which led to a nobel prize in medicine won by Dr Stanley Prusiner in (IIRC)), 1998.

The previously unknown agent was named a prion, and is likened in the book to a slow-speed virus, one which takes twenty or so years to activate.

Further research has determined that prions are crystals, which disrupt some fundamental biological activity in the brain, causing the body to conume it.

This self-consumption leads to the presence of holes in the brain tissue, hence the use of the term spongiform encephalopathy.

The book is a good read and quite well written.

So well written that I gave up meat shortly after finshing it.

And why did I call this whole thing sick?

The practice of feeding dead animals to other animals is nothing new; it's been done for centuries.

What is new, however, is how these body parts are disinfected.

The recent outbreaks of this disease were caused solely by financial considerations. The meat industry changed how they disinfect tissue to a cheaper process involving heat instead of the previously used chemicals.

Apparently prions are NOT destroyed by the heat, and then can infect animals up the food chain.

That includes humans, by the way.


New Research shows that prions may not be the cause of BSE

Bovine spongiform encephalopathy, colloquially known as 'Mad Cow Disease' or by its acronym BSE, is a neurological disease of cattle which first appeared in the UK in the early 1980's following changes in the way in which winter feeds were prepared. The explanation accepted by the British government is that this disease is caused by prions, protein fragments which have been observed in scrapie-infected sheep. The use of abattoir offal, which may have included scrapie-infected sheep, in the production of winter feeds could have transmitted this disease to cattle.

However in early 1996, a paper appeared which suggested that scrapie could not be transmitted between SCID mice. This demonstrated that the disease was neither infectious nor contagious, but probably caused by the immune system of the animal itself. Researchers at King's College London have therefore proposed that BSE is an autoimmune disease caused by infection with microbes containing sequences which crossreact with the nervous tissues of sheep or cattle. This explanation has a similarity to the cases of ankylosing spondylitis and rheumatoid arthritis, both autoimmune diseases caused by Klebsiella and Proteus bacteria respectively.

It has been known since Pasteur first experimented in th 1880s, that the injection of brain tissues into allogeneic animals causes a neurological disease known as experimental allergic encephalomyelitis. EAE is characterized by tremors, paralysis of the hind quarters and eventual death: all features that are frequently observed in BSE.

Chronic EAE was demonstrated in 1969 to be characterized by the spongiform appearance of the brain, similar to the histological features observed in BSE or scrapie. Computer analysis of immunogenic sequences of bovine myelin were cross-referenced against bacterial protein databases and the microbe with the closest sequence to bovine myelin was found to be acinetobacter, a common saprophytic microbe, present in large quantities in soil, sewage and green offal. A sequence in the bacterium Escherichia coli (E. coli) was also identified which was similar to the prion protein. Accordingly, sera obtained from BSE cattle were tested for antibodies to acinetobacter and compared to healthy animals and it was found that BSE infected cattle contained elevated levels of acinetobacter antibodies.Raised levels of the antibody were also found in two cases of vCJD, and among patients with multiple sclerosis.

The conclusion reached by the researchers was that BSE is a neurological, autoimmune disease which occurs after cattle are exposed to acinetobacter bacteria. The recent outbreak of BSE in the UK is thought to be the result of inadvertent contamination of cattle's winter feeds with acinetobacter bacteria.

Official sources find problems with this theory, (see, claiming that proteins in the bacteria would be denatured by the heat pasteurisation process. However, they have yet to come up with a convincing explanation for their assertion that prions, which are after all protein fragments, would not be damaged by this process. It seems more likely that prions are symptomatic of the brain damage than its cause.

Professor Alan Ebringer - King's College London

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