Wednesday, March 09, 2005

Why for you bury me in the cold, cold ground?

...a statement which Taz could be asking very soon, but not of Bugs Bunny.

An article in Science (Vol 307, Issue 5712, 1035, 18 February 2005, summary) recently drew my attention to something that has bothered me for years.

For some reason, probably to do with the context in which I learned the word, a disease has always seemed to me to be something that was communicable, or that at least had some kind of vector. So things like leprosy, measles, malaria, influenza were diseases, while things like cancer, diabetes, Krohn's etc. were not. I would have called these latter things 'conditions.'

I now know this is not how they are defined medically, and that there is probably medical or epidemiological terminology to describe exactly the kind of separation I describe above, and that I still feel echoes of today when I hear the word 'disease' used to describe things that cannot be transmitted from one individual to another.

...or am I sure? The Science article describes a facial cancer that has been observed to be increasing in frequency among Tasmanian Devils. The disfiguring facial cancer eventually grows so large that it interferes with the creature's feeding, and they starve to death. The point in the article that stunned me was that this cancer seems to be spreading because the Tasmanian Devils are in fact spreading cancerous cells to each other as a consequence of the vicious fights they normally enage in, including biting each other's mouths. In other words, this is a cancer that is a communicable disease. Evidently these cancer cells can get around the self/non-self signals that are the basis for most immune systems. This is a cell that is not exactly some other form of life, but a mutated version of self.

I think this is more evidence that Nature loves these grey areas, and always holds a surprise, like a sort of fractal.


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