Mad Cow Disease (BSE) for Dummies
I did NOT write this. A friend of mine (4th yr medical student, majoring in forensic investigation) from Canada did.
Ok, first off, we have to define the illness itself:
Bovine Spongiform Encephalitis is a fairly rare and obscure neurological disorder. It is untreatable,
incurrable. It belongs to a family of rather poorly understood disorders. There are human variants, and
ruminant variants, most commonly known as BSE.
Now, you are going to need to understand a couple of differences between normal viral/bacterial diseases
and illnesses like BSE.
Everyone here I'm sure has a vague idea of what viral and bacterial infections are. But for clarity:
Bacterial infections are generally caused by colonies of autonomous animals called, surprisingly enough,
bacteria. They infect the host, and breed. Sickness is generally the body's response to the invader.
Bacteria are fully functioning individuals that depend on the host to provide an appropriate
breeding ground. Bacteria vary widely in size, but tend to be fairly large, relative to other pathogens
and body cells.
Viral infections are a little more complicated. There is much debate as to wether a virus is even a "living"
thing. At least, depending on your definition of life. Simply put, a virus is little more than a half
complete cell, with a partial DNA strand, with very few actually WORKING structures. However, when introduced
into a host, the virus inserts it's DNA into the host cell, effectively changing the cell's function.
Think of it as a brain transplant. The modified cell then has the instructions for creating MORE
virii, and the cycle repeats. Physically, virus cells are extremely small
Finally, we have what is called a Prion. A Prion isn't even a half-complete cell. A prion is a malignant
strand of DNA that wanders around waiting to be picked up and used. Your body manufactures uncounted billions
of mRNA strands at any given time. This is the messenger boy from your DNA to your body. When your body
needs to create a protein, it pumps out the portion of DNA that describes the protein with a protein
called transcriptase. The new mRNA then floats around until it gets picked up by a chunk of protein
called reverse transcriptase, which decodes the mRNA into the desired protein. The mRNA strand is then
usually destroyed.
Now, the prion enters the host cell, gets picked up by the transcribing protein makes the protein, but
then gets spat back out intact. To repeat the cycle.
BSE is a Prion disease. The protein that the prion creates is an enzyme that has the ability to break
apart nervous tissue.
Now, what does all this mean? First, you can't transmit BSE like a normal viral or bacterial agent.
Neither can you kill or deactivate BSE by heat or disinfectant, since it isn't alive. Most proteins
tend to denature at around 50º. The prion responsible for BSE doesn't. About the only thing that
can effectively "kill" BSE is incineration.
Also, since BSE manifests as a metabolic disorder, there is not much you can do to DETECT the illness.
Any and all cases of BSE are discovered posthumusly, since there are almost NO effects from the disease
until very late in it's stage. When you cross-section the skull of the infected animal, the brain
appears to be a spnge-like mass.
The human variant, Cruetzfeldt-Jacob disease is much the same. The infected individual may not exhibit
any effects until 10, 15 years after initial infection. Afterwhich, the disease progresses much like
Alzheimers; Memory loss, loss of cognitive funtion etc. In addition, the individual may display
symptoms of any number of neurological disorders; depression, schizophrenia etc.
So, most cases are misdiagnosed anyway. The unfortunate part is even if it were diagnosed, there is
nothing that can be done about it at present, except treat the symptoms, and wait for eventual death.
As mentioned earlier, prion diseases cannot be transmitted by "normal" means. The prion isn't a free-
floating agent, spore, seed, or growth. It is a chemical that resides in the cellular material of the
infected animal. The ONLY way to acquire it is through consuming infected tissue.
This is where it gets weird; The prion responsible for the disease is only found in the NERVOUS tissue.
Which means that unless you are habitually eating entire beef-brains, you aren't likely to catch it.
Furthermore, unlike viral infections, the prion doesn't self-replicate. This means that C-J is a
culmulative disorder; how fast it progresses depends on the number prions incorporated.
Tests done to mammals suggest that a hamster has to be INJECTED with the raw protein on the order
of 100,000 units of the raw prion material to begin exhibiting symptoms. The amount or NERVOUS tissue found in most meat is measured in milligrams.
Which means that if you eat only T-bones, you'd have to consume several tons of INFECTED meat to stand
a reasonable statistical chance of getting the disease. And THAT is assuming 100% uptake of the
prion.
The human body isn't all that efficient at it. Even if you eat the meat, there is VERY little chance
that ANY of the prions will find their way into the nervous tissue.
So, to conclude, let's summarize and assess:
1) C-J is a horrible, horrible disease.
2) It's caused by a non-living chemical that gradually builds up in the body.
3) The chemical is ONLY found in the nervous tissue of infected animals.
4) The human body doesn't usually pick up the prion on it's own when eaten
Conclusion: It's not a terribly huge health risk, unless you have a passion for beef-brains.