Bovine spongiform encephalopathy
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Though it is rare in humans, we can contract the disease through eating infected meat (but don't worry, if you die of CJD, it's much more likely you'll die of the form unrelated to cows). CJD debilitates and later kills the infected person, taking between eight weeks and a couple of years, and is 100% fatal.
The brains and spinal cords of infected animals are considered more infectious than other parts, and there are thus "rules against beef processors using the brains or spinal cords of the animal to make food products".
Our best theory as to the mechanism behind Mad Cow Disease, and other transmissible spongiform encephalopathies, is that it's not caused by a virus or a bacterium or a parasite or a congenital condition, but instead by a misfolded protein called a prion.
Prions are fascinating molecules. Like all protein molecules, they are chains of amino acids. In general, every protein molecule in your body does its job because of its shape; the way a given amino acid chain is "folded" in three-dimensional space determines what kinds of other molecules it can capture, latch on to, twist apart, etc. Normally, every amino acid chain will fold in one specific, predictable manner as it's being assembled from one end to the other. However, in a few cases, the same amino acid chain can be folded into a very different shape after it's been assembled, if it's acted upon by the proper outside force. This will make the molecule incapable of performing the duty that its old shape had.
Prions (PrPSc) are, amino-acid-for-amino-acid, identical to a nerve tissue protein called PrPC. However, they're folded in a radically different manner, which causes them to be extremely protease resistant, almost impervious to disinfection, and one of, if not the most powerful toxin in the world. They act as catalysts to re-fold PrPC into new prions. Thus, one prion will, when introduced into neuronic tissue (such as brain tissue), create more PrPSc
This quasi-self-replicating behavior has led some to speculate as to whether prions should be considered a form of life (but, like viruses, prions do not respire, which is by some definitions a requirement for life).
Frustratingly, prions don't break down in the presence of acid or heat — their new structure is far more stable than PrPC. This means that neither cooking, nor the digestion process, can remove prions from infected cow brains.
Cows were not the first species known to be infected by prion diseases. The sheep disease scrapie is now known to be very similar to mad cow disease. It first reached epidemic proportions in cows, however, due to the practice of grinding up the undesirable parts of a slaughtered cow (including the cow's brain) and feeding this protein meal to other cows. Since the alarm bells were raised for mad cow disease, this practice has been discontinued.
- Bovine spongiform encephalopathy from Wikipedia
- The Official Mad Cow Disease Home Page
- What’s Mad Cow Disease?
- Risk of death from variant Creutzfeld Jacob Disease (vCJD) and CJD in the UK (2007) Bandolier, University of Oxford (archived from April 17, 2015).
- What is Mad Cow Disease?
- Eligibility Reference Material American Red Cross.
- Mad Cow Research: Small Steps, Big Questions by Amanda Onion January 6, 2006, 5:56 AM) ABC News.
- Alien invasion and mad cow disease by Peter Farley (2006-12-12) 4TruthSeekers.org (archived from July 31, 2016).
- Doppel: More rival than double to prion by Kefeng Qin et al. (2006) Neuroscience 141(1):1-8. doi:10.1016/j.neuroscience.2006.04.057.