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Chapter 5: Of Microbes and Men
Transcript of Chapter 5: Of Microbes and Men
The Guinea worm is a parasite that live in the human intestine. Once it reaches adulthood, the adult worm will make their way to the skin of the human host. Before people could surgically remove the Guinea worm , the only effective way to get rid of the Guinea worm was to wrap the worm around with a stick and slowly remove the parasite. Many scholars believe that the Rod of Asclepius, an early symbol of medicine, depicts a guinea worm wrapped around a stick, which was used to indicate that a certain doctor can treat the guinea worm.
Taking yogurt and antibiotics is a good combination because the compounds in the yogurt protect the friendly bacteria in your digestive tract. Most antibiotics cause damage to all of the bacteria inhibiting in the human body, including intestinal bacteria that aids in digestion. This causes a person who is taking antibiotics to have digestive problems since the antibiotics destroys the bacteria in the digestive tract. However, yogurt contains bacteria that are helpful to humans and can provide digestive aid that is normally provided by the gut flora until the gut flora can get back into regular levels.
An interesting example of host manipulation is the rabies virus. It infects the salivary glands of the host. This makes it difficult to swallow, forming the characteristic foaming of the mouth, with rabies-filled saliva in the foam. While this happens, the virus infects the brain, making the host aggressive and agitated. This manipulation of the organism causes it to bite others near it. Because the foam is filled with the rabies virus, the organism bitten will become infected, with the virus entering the body through the bite wound.
The common cold is not very virulent because it relies on the infected host to transmitted the disease by sneezing to introduce the virus to new hosts. This means that the common cold leaves the host in healthy enough condition so that the host can transmit the disease to others.
Chapter 5: Of Microbes and Men
Stephen Chen and Colin Philips
The more virulent diseases typically are transmitted through intermediate organisms (such as mosquitoes with malaria) or use transmission channels (such as the water supply for cholera). Because they do not need the host to spread the disease physically, they tend to do great bodily harm and incapacitate the victim. For example, the malaria virus uses mosquitoes to transmit itself. In order to spread the greatest amount, it attacks the host's body to make it too weak to move. The then immobile and helpless being is then easy prey for the mosquitoes to suck malaria-filled blood from. It seems that transmission through an intermediate organism is more effective and harder to treat. Transmission channels can easily be blocked and therefore preventing further infection.
As stated earlier the more virulent viruses seem to use transmission channels or intermediate organism. Because they have no use for the organism for transmission, they do not hesitate to cripple the host and attack it.
The least virulent viruses have the tendency to actually use the host in order to spread the viruses. For example, the pin worm is a parasite that typically infects children. It matures and mates in the large intestine of the host. Once pregnant, females are excreted by the host and lay eggs on the skin of the child. At the same time, the females release allergens that cause itching. The child in response itches the area and unintentionally lodges the eggs underneath his/her's fingernails. The child then spreads the eggs by touching other things. The pin worm doesn't actually harm the host because it needs it in order to spread. The dependency on the host has a direct connection to the virulence of a parasite: the more dependent, the more virulent; the less dependent, the more virulent.
In the survive-and-produce race, humans have a huge advantage. We have the ability to think and analyze our enemies (in this case, parasites and infectious organisms). We have been able to study and interpret the mechanisms of deadly organisms, like cholera and malaria, and actually have become to understand their modes of evolution. We are, as the author put it, simply smarter than them. A new theory scientists and biologists have developed in this "war" instead of constantly developing new antibiotics, is to actually manipulate the evolution of these beings to our benefit. It is possible we can make deadly bacterias, like cholera, into less deadly invaders by increasing their dependency on humans for transmission. In order to do this, for example, on cholera, we would need to secure our water systems and make them more hygienic in order to undermine its ability to spread without humans. This idea to manipulate evolution to benefit humans will also allowing for the survival of bacterias may be monumental steps in the "war". There is no doubt that our ability to analyze and problem solve is our biggest advantage.
Three ways microbes/parasites can transmit themselves and their offspring are through the hosts (such as sneezing), through intermediate organisms (such as rats), and through transmission channels like the water supply).
A good example of transmission through the host is the common cold. It uses the hosts (in this case people) ability to sneeze to spread to other organism. That is why you tend to sneeze a lot when with the cold.
An example of intermediate transmission is malaria. The malaria bacteria uses mosquitoes to transmit themselves to other hosts.
An example of transmission through channels is cholera. It infects other organisms by contaminating the water supply and taking root in hosts after being ingested.
Dobzhansky's quote is an idea deeply imbedded within this book. Dr. Moalem repeatedly provides examples showing that evolution is the key to our existence today and has shaped nature as it is today. An interesting topic Moalem brings up is our defenses against microbes and parasites. You would think after thousands of years of being infected, humans would have evolved a natural defense. However, this anomaly is simply explained by the evolution of the microbes along with us. In short, evolution, the will to live, explains even the most difficult concepts of biology.
This book is an extremely enlightening and interesting novel. Moalem provides great examples to his theories and backs it up with simple explanations.
Moalem, Sharon, and Jonathan Prince. "Of Microbes and
Survival of the Sickest: A Medical Maverick Discovers Why We Need Disease
. New York: William Morrow, 2007. N. pag. Print.