Lots of cats in the news lately. Some readers have been writing to me about that news and we talked about it over dinner last night with friends. Now it has also infected
a stone marten:
http://news.yahoo.com/s/ap/20060309/ap_on_he_me/germany_bird_flu;_ylt=Arzl7u_3ltd.lYBaTszE0p1a24cA;_ylu=X3oDMTA3czJjNGZoBHNlYwM3NTE-
As I see it there are three very different concerns:
CONCERN ONE: Most scary is the idea that we could catch the flu from the cat. While this does not seem to be happening, it cetainly seems a tnreat to have the living virus right in the house with you. One question would be if in cat feces the virus was alive and ready to infect people. So far there has been no cases of the virus moving from cat to person.
The thing keeping us fom getting bird flu is that the receptor binding protein in the virus is not a good fit for humans. Here is a description of how that works:
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How do viruses reproduce?
All viruses reproduce by taking over the reproductive mechanism of a host cell, so the first thing a virus must do is get into a cell by passing through the cell's membrane. They do this by means of their receptor-binding protein. These proteins are encoded in the viruses' genetic material and they stick out from the surface of the virion. They are attached either to the capsid or part of the envelope, depending on the type of virus. These proteins cause the virion to bind to specific receptors on the host cell in a manner similar to the way a key fits into a lock. This interaction between the host cell's receptor and the virus' receptor-binding protein is crucial and causes the "specificity of infection". This specificity usually limits a viruses' infection to specific types of cells and specific animals (or plants or bacteria) depending on the virus.
For example, HIV (the virus that causes AIDS) has receptor-binding proteins that attach to specific types of human white blood cells. Because of its specific receptor-binding protein, HIV cannot infect skin cells or lung cells so it is not infectious by touch or by breathing it in. In addition, HIV does not infect monkeys because the receptors on monkey cells are not the right shape to accept HIV's receptor-binding protein. However, a related virus, called SIV, can infect monkey cells because it has evolved a receptor-binding protein that attaches to monkey white blood cell receptors.
The interaction between a viruses' receptor-binding protein and the host cell's receptor(s) is an on going battle in molecular evolution. The specificity may change as the virus evolves a new gene for its receptor-binding proteins or the host cell evolves new genes for its receptors. This evolution can produce viruses that unexpectedly switch to a new host; either a new type of tissue or a new type of animal.
from: http://www.synapses.co.uk/science/fluvirus.html
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So people who get rid of their cats because they feel they might cath the flu from them may be overreacting. On the other hand a few months ago people who got rid of pet chickens were also believed to be overreacting. This same article says that. Now it does not seem to be overreacting to get rid of pet chickens.
CONCERN TWO: The real scientific fear is that the cat is sort of an experiment to see if this virus has the opportunity and the will to evolve into something that will infect other animals. It is all a crap shoot. But when the dice roll "yes" for the cat, it seems more likely that they may roll "yes" for us. The odds are still huge, but remembering the lottery analogy, every spreading infection among bird populations is the virus buying yet another lottery ticket toward having a reeptor-binding protein that fits humans.
CONCERN THREE:
If nothing else, it looks like a lot of cats are going to die as the flu spreads. Many others will be abandoned by owners, some to shelter and some just set free. This is already the case in Europe.
http://www.channelnewsasia.com/stories/afp_world/view/196918/1/.html
http://www.channelnewsasia.com/stories/afp_world/view/196859/1/.html
http://www.timesonline.co.uk/article/0,,3-2076346,00.html
http://news.bbc.co.uk/2/hi/health/4787234.stm
Note that this is not really breaking news. It is just that we don’t get much variety and no depth in our news, just the same stories over and over with sound bites.
http://news.nationalgeographic.com/news/2004/09/0902_040902_birdflu.html
http://www.newscientist.com/article.ns?id=dn6352
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