Mad cow disease, or bovine spongioform encephalopathy (BSE),
is a prion disease. Prion diseases are a group of rare communicable diseases
affecting both humans and animals. They are progressive degenerative diseases
of the brain, characterized by the spongy texture of the brain (or holes in the
brain) and dementia. Prion diseases have a long incubation period and are
invariably fatal. The cause is infectious abnormal prion proteins in the brain
and spinal cord, which are folded and distorted, and which can contaminate normal
prion proteins, causing increasing damage to the brain.
Besides BSE, prion diseases in animals include Chronic
Wasting Disease (in deer and elk),
Scrapie (in sheep and goats) and similar diseases in mink, felines and
ungulates. Human prion diseases include
Creutzfeldt-Jakob Disease(CJD) and a variant of CJD, Gerstmann-Straussler-Jakob
Syndrome, Kuru and Fatal Familial Insomnia. The disease can occur spontaneously
for unknown reasons, it can be inherited (fatal familial insomnia) and it can
be transmitted through the food chain when the brain or spinal tissue of an
animal with mad cow disease is eaten by humans or by another animal (kuru.)
Mad cow disease was first discovered in Britain in 1986 and
it killed approximately 150 people and 184,000 cattle. It was caused by widespread
use of meat and bonemeal cattle feed made from scrapie-infected sheep. People
who died from the disease were probably exposed to it by eating processed beef
contaminated with BSE. Since then the U. S., Europe and Canada have banned
feeds produced with the meat and nerve tissue of animals, significantly
reducing the transmission of BSE.
How likely is it that any of us will contract prion disease
from meat? The infectious protein isn’t found in muscle, just in brain and
spinal cord tissue, so it’s likely that eating steaks, roasts and so forth is
safe. Processed meat is slightly riskier as it is made from many varieties of
meat, including tissue stripped from the spine by the processing machines.
Current laws and meat processing procedures are designed to
prevent the spread of BSE to animals or humans. So the question is whether you
trust that everyone in the meat processing industry scrupulously follows the
safest procedures. It’s highly unlikely, statistically speaking, that any one
of us will get prion disease from eating contaminated meat. However, if you don’t
want to be the first person in the U.S. to develop BSE from meat, the solution is
to not eat beef, goat, sheep, elk or deer, and especially to not eat processed
meat.
The Family That Couldn't Sleep: A Medical Mystery. Max, D. T. 2007
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