Mad Cow Disease

Mad cow disease (MCD), also known as Bovine Spongiform Encephalopathy (BSE) is a degenerative neurological disease found in cattle. It causes holes to be eaten into the brains of infected animals, making their brains resemble a sponge - it is 100% fatal to cows. The average incubation period for BSE in cattle is around 4 yeas. It is widely believed by most of the scientific community that BSE can be transmitted to humans by eating the brain, spinal cord and in some cases, even the meat of infected cows. In its human form it is thought to be a variation of Creutzfeldt-Jakob disease (vCJD). Varient Creutzfeldt-Jakob disease closely resembles BSE and is also 100% fatal to humans.

The origins of BSE are somewhat unclear, but the first official cases appeared in the mid-1980s when an outbreak of the disease was seen in cattle herds in the United Kingdom. The causes of BSE are only theorized. The theory goes something like this: in order to save money on cattle feed, cattle producers decided it would be cheaper to recycle slaughtered cattle remains (the parts that people don't eat) by grinding them up and rendering the product into cattle feed for living cattle. So basically, they were feeding dead cows to live cows. The meat and bone meal products from the dead cattle are thought to contain dangerous protiens, called prions (PRE-ons), which cause BSE. These prions were previously only found rarely in cattle populations and were not a significant problem. But because the "dead cattle feed" was produced on a mass scale and in a haphazard way, the infectious agent was probably concentrated in the feed. And when cows ate this feed...you guessed it - mad cow disease was born.

There seems to be a couple of main factors which contributed to the genesis of mad cow disease. Firstly, cattle are natural herbivores and they do not consume meat. The introduction of forced cannibalization in the cattle producing industry seems to be upon retrospect, a big mistake. Prior to 1987 this practice was widespread in Europe because it was deemed too expensive to grow the crops necessary to feed cattle. Secondly, in Britain, a law was loosened that permitted a lower temperature of sterilization for the rendered cattle carcasses used to produce this "cattle feed." Had they used a higher temperature of sterilization it may have been effective in killing the infectious agent. This gives new meaning to the phrase "don't mess with Mother Nature."

The origins of the human form of BSE are harder to trace because the average incubation period of the disease has been found to be up to 15-20 years long. This would suggest that people were initially exposed to the disease well before the mid-1980s because the first official case of vCJD (the human form of BSE) was in 1992. It was then that an 18-year-old young man was diagnosed with the disease in Britain. Before this, the British government had denied that BSE could be transmitted to humans. Shortly after this young man died in 1995 the British government did admit that humans can contract the disease from eating contaminated beef. The death toll from vCJD in Britain now stands at over 160.

Measures have been taken by various governments around the world to stem the spread of BSE in cattle and the transmission of vCJD to humans. These measures include wholesale slaughter and eradication of large herds of cattle, bans on feeding cattle the most infectious parts of the rendered carcass (the brain and spinal cord), and import limitations on beef from countries suspected of having high rates of BSE in their cattle population. These measures seem to be having some positive affects on the transmission of BSE. The reported cases of BSE in the global cattle population has declined since its peak in the early 1990s. Unfortunately, because of the long incubation period of vCJD, it may be some time before we know what affects these measures will have on the transmission of this disease to humans.

Sources:
Sean Henahan "MAD COW DISEASE
The BSE Epidemic in Great Britain" An Interview with Dr. Frederick A. Murphy
Dean of the School of Veterinary Medicine, University of California Davis
Barry Mason " Barry Mason: Britain: New wave of human BSE/vCJD feared" Creative-I: Trying to make sense of things in this crazy, capitalist world and then change it
" Bovine spongiform encephalopathy" From Wikipedia, the free encyclopedia