Survival of the Sickest Part III

What Did You Think About the Reading?

I’m not entirely sure I processed everything I read in these two chapters because there was just so much information! Once again, several interesting scientific facts and experiments were presented and each one was somehow tied and connected to another. What I found most interesting was the discussion about host manipulation. Some of the examples were almost unbelievable! For example, there is a parasite called Toxoplasma Gondii (T. gondii) that can only survive in cats, even though it can infect just about every other warm-blooded animal. When an animal gets infected by T. gondii, the parasite goes through the blood stream and while distribute its cells to the infected animal’s muscle and brain cells. But here’s where it get’s interesting: When T. gondii infects mice and rats, the parasite goes into the rodent’s brain and muscle cells, similar to what happens in other animals, and actually starts influencing the rodent’s behavior! The mouse or rat will first become lethargic and fat. Then, the mouse or rat will actually become attracted to its predator- the cat. And when a slow and disabled mouse is willingly hanging around cats, the cat will catch the mouse and thereby ingest the parasite T. gondii. Now the parasite is exactly where it wants to be- the only animal that it can survive in. In my opinion, this is absolutely remarkable how an organism as small as parasite can influence such a monstrous animal (compared to a parasite) in this way.

What Did You Learn?

As mentioned above, I learned many things about host manipulation. But what I found to be equally as interesting was the discussion about illnesses and how they are transmitted. When it is a simple illness, such as the common cold, sneezing is a common method for the virus to get out of the invalid’s body and into another person’s body. For more serious illnesses, however, it gets a little more complicated. Cholera causes severe diarrhea, an excellent transmission channel for the virus to make it into the water supply to find new hosts. The two main goals of infectious agents (As with any organism) is to survive and reproduce. The amount of damage an organism does to its host is known as virulence. The cold virus has very little virulence (the invalid is still mobile and can carry on with just about every activity they normally do) while cholera has a much higher virulence. An interesting idea that was presented in the novel was that if we were able to change the bacteria so that it could only reproduce by getting the invalid to move around, then we could change the virulence of the organism. Experiments surrounding this idea have already been conducted with great results. With cholera, for example, if the water supply was highly protected then the organism would have a much harder time getting access to a new host. For the infectious agent to survive, it would then have to lessen its virulence in order for the invalid to become mobile and spread the disease through human contact. When studied in Chile, this idea was supported- The safe water supplies caused the bacteria’s virulence to go down and killed fewer people.

After discussing how infectious agents can evolve to change their virulence, Dr. Moalem explains human DNA and how 97% of it is non-coding (or “junk”) DNA. A recently learned, interesting fact about genes is that they can jump! In fruit flies, for example, a jumping gene can turn one line of fruit flies into a line that is immensely stronger than the last line (the jumping gene can make the fly resistant to starvation, withstand high temperatures, and have a life expectancy that is 35% longer than normal). In humans, jumping genes are very important in the early development of the brain. This jumping actually contributes to our individuality. In addition, jumping genes help us produce the  millions of antibodies for our immune system. If researchers can understand more of how this process works, they could possibly help them develop more ways to immunize people, restore damaged immune systems, and even reverse mutations. 

What Questions Do You Still Have?

Some questions I still have include: Could we make all (or a lot) of infectious agents’ virulence decrease, similar to what we have done with cholera in Chile? Although it may be expensive, I think it would definitely be worth the cost for all of the lives it would save. Also, since antibiotics kill a large amount of our bacteria (including the beneficial kind), could it be possible for scientists to develop an antibiotic that targets only the harmful strand? This could make antibiotics, and our bodies, even more efficient. Finally, if humans are subject to host manipulation from nearly microscopic organisms, would it ever be conceivable for humans to manipulate other humans in this way? If this were ever possible, the side effects would certainly be terrible as it would definitely fall into the wrong hands very quickly and is not ethical to begin with.

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One thought on “Survival of the Sickest Part III

  1. I also found Dr. Moalem’s discussion of host manipulation extremely interesting and slightly unsettling. To answer your question if host manipulation could be used on humans, i think that it is completely possible, and that people are already working on that form of biological warfare. Also, I hope that it is possible to decrease the virulence of all, or most of mankind’s diseases, Lastly, I feel as though it would be possible to develop specific antibiotics, but it would be extremely expensive, and difficult.

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