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Has The Mad Cow Epidemic Gone Away?

By James Donahue

Michigan deer hunters last fall were urged to have the meat of the animals they bagged tested after random state exams found cases of Chronic Wasting Disease in a few bucks on the Northern Peninsula.

While most people watching this televised news report may not have connected the dots, state game and health department officials were warning hunters that the deadly prions known to bring on bovine spongiform encephalopathy, or “Mad Cow Disease” had been found lurking in the forests of Michigan.

While the Mad Cow Disease epidemic of the early 1990s that brought about the mass slaughter of hundreds of thousands of cows around the world appears to be under control, researchers are still keeping a watchful eye on the herds of not only the beef cattle, but also sheep, deer and other forms of livestock consumed by humanity.

That is because the Mad Cow prion is found to jump from species to species, even showing up in birds, cats and humans. It spreads not only by the consumption of infected meat, but through the air, according to a report in the January issue of Scientific American.

The story by Philip Yam states that researchers at University Hospital Zurich found that the prion could be passed to laboratory mice via aerial sprays. The discovery adds a new dimension to the potential danger hiding out in these microscopic bits of abnormal protein.

Indeed, prions are proteins that are naturally produced in the bodies of all animals. In the case of the Mad Cow Disease, it was discovered that toxic mutant versions of prions were created by the practice of grinding up bones and other non-marketable animal parts and turning it into livestock feed. What that amounted to was forced cannibalism among the cattle.

Yam described the result when he wrote: “These malformed versions can cause normal prions to become pathogenic, setting off a chain reaction conversion to the deadly kind. The bad prions destroy neural tissue, sometimes leaving the brain full of holes like a sponge.” This is why the disease has the technical name of spongiform encephalopathy.

All farming operations throughout the world stay in contact with one another, usually through agricultural researchers at major colleges and universities, so feeding practices used successfully in one part of the world are quickly picked up and used everywhere. Thus when farmers in the UK came up with the idea of grinding up waste parts of slaughtered cows and adding them to the cattle feed, it sounded like a good way to add protein to the feed and make good use of material that normally had to be disposed of. Thus it was not long after Mad Cow Disease broke out in the UK, cases began turning up all over Europe, the United States and other countries of the world.

Even worse, the prion had already spread to humans in the form of Creutzfeld-Jakob disease. People who had eaten the tainted meat were infected.

Deer and other wild animals that easily jump fences and feed from open farm feed troughs designed for beef cattle, began dying from what was called Chronic Wasting Disease. In the sheep it was called “scrapie.”

Different names, but all the same thing. All suffered from spongiform encephalopathy, brought on by mutant prions that got into their feed.

The disease by whatever name we choose to call it is insidious. As the mutant prions destroy neural tissue, it eats holes in the brain. Humans suffering from Creutzfeld-Jakob disease go insane and eventually die. Autopsies show that after death, the brain tissue looks like a block of gray Swiss cheese.

After the UK cattle began going crazy and dropping dead in the early 1990s, the cause of the problem was not known until Dr. Stanley Prusiner of the University of California found that the prion was the common thread linking all of the brain diseases. Prusiner was awarded the Nobel Prize in medicine for his discovery in 1997.

While classified as a protein, prions in mutant form are an indestructible disease-causing substance. They are living organisms although scientists cannot classify them as viruses, bacteria, fungi or parasites. They are a combination of 20 amino acids that attack brain tissue

As researchers studied prions they found that they survive the pressurized steam of autoclaves, filtration, extreme heat, radiation, formaldehyde and decades of freezing. They cross species and can be spread not only by ingestion and aerial application, but through blood transfusions and feeding on infected meat. Cooked meat does not protect the consumer.

Because of its nature, blood tests do not exist to determine the presence of spongiform encephalopathy in humans, livestock or stored blood. The only way to determine the presence of the prion is by examining brain tissue after death.

So how dangerous is the meat we buy from today’s supermarket?  We are glad to say that once the cause of the Mad Cow nightmare was discovered, world farming practices have changed and mad cow disease has been brought under control. Yet occasional cases still turn up.

According to the World Organization for Animal Health, only seven mad cow cases occurred in the UK in 2010. The United States reported only two cases in 2004 and 2005. Thus the chance of that hamburger frying your brain into Swiss cheese has been reduced almost to zero.

Still, there was that alarm about infected deer in Michigan.