True: Prions are not alive and therefore you can't kill them.
I think, though, that we don't have any good idea on who is susceptible to mad cow, or at least who is more susceptible. And there is no good way to do a dose-response study on a disease that seems to only affect humans. I have a untested and unproven theory that in carcasses of such animals, using some kind of solvent to denature the proteins should destroy also the 'rogue proteins'. The problem would be the environmental impact of using denaturing agents on such a large scale.
This is the NIH laying down the SCIENCE on y'all.
BTW, for those of you who actually watched that silly "medical investigations" show, the NIH has no field staff. That's us at CDC. And we don't really work the way the clowns on the show do, either.
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Adapted from
Prions: Puzzling Infectious Proteins by Ruth Levy Guyer, PhD
Prions have changed scientists' understanding of the ground rules for infectious diseases. Prions cause diseases, but they aren't viruses or bacteria or fungi or parasites. They are simply proteins, and proteins were never thought to be infectious on their own. Organisms are infectious, proteins are not. Or, at least, they never used to be.
Prions (pronounced pree-ahns) enter cells and apparently convert normal proteins found within the cells into prions just like themselves. The normal cell proteins have all the same "parts" as the prions--specifically the same amino acid building blocks--but they fold differently.
Prions enter brain cells and there convert the normal cell protein PrPC to the prion form of the protein, called PrPSC. When normal cell proteins transform into prions, amino acids that are folded tightly into alpha helical structures relax into looser beta sheets. More and more PrPC molecules transform into PrPSC molecules, until eventually prions completely clog the infected brain cells. The cells misfire, work poorly, or don't work at all.
Ultimately, infected prion-bloated brain cells die and release prions into the tissue. These prions then enter, infect, and destroy other brain cells. And, as clusters of cells die, the brain stops looking like a brain and starts looking more like Swiss cheese. The medical term for the prion diseases is "spongiform encephalopathies," in acknowledgement that the sick brains (encephalo is Greek for brain; pathy is Greek for disease) are riddled with holes and have taken the form of sponges.
Shepherds and farmers whose sheep had scrapie never seemed to get scrapie themselves. So, for a long time, scientists assumed that the prions of animals did not cause infections in humans. But, between 1994 and 1996, 12 people in England came down with Creutzfeld-Jakob disease (CJD), a human prion disease whose symptoms are not unlike those of the mad cows, and all the victims had eaten beef from cows suspected of having mad cow disease. In October, 1996, scientists in England reported that the prions from ten of the British patients were remarkably like those of the mad cows and not like those of people who died of "classical" CJD.
Scientists quickly realized that the occurrence of CJD in a dozen people 19 to 39 years old was cause for alarm, because CJD had always been rare--typically one new case might be diagnosed per million people each year--and seldom occurred in people younger than 55. This epidemic was something new, something extraordinary. Scientists now speculate that the prions that started out in sheep suffering from scrapie made their way into cows and then moved more recently into humans.
Cattle are fed meal made from sheep "offal," the bones and other waste parts of sheep carcasses. Standard procedures for grinding up carcasses were altered in the 1970s, and the new processing methods seem not to have been adequate for destroying scrapie prions. The cattle were exposed, through the offal, to sheep prions, and the prions eventually established themselves in their cow hosts. Later, they adapted further, infecting cells of people who had eaten hamburgers from prion-bearing cows.
At the moment, CJD and only a handful of other human diseases have clear links to prions. But it is likely that prions will turn out to be the agents of a variety of currently enigmatic diseases in which brain cells are destroyed and the nervous system deteriorates. Alzheimer's disease and Parkinson's disease are two prime candidates.
So, a couple new ground rules now seem to govern infectious diseases. The first is that naked proteins--prions--can be infectious and can cause infectious diseases. The second and potentially more troubling is that, like other infectious agents, prions can jump species' barriers and cause deadly diseases in humans. Recently, and for the first time known, two farmers with mad cows in their herds died of CJD.
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