On page 122-123, Dr. Moalem mentions that according to Ewald's theory, "bacteria have an advantage over us." Moalem later goes on to mention that this is not some sort of "arms race" between humans and bacteria, to see how we can kill of bacteria before they figure out a way to resist our anti-biotics. This relates to big Idea number 1, because Moalem mentions how evolution has helped bacteria to progress and sometimes become harmful to humans, and where we humans want evolution to end, in terms of ending bacterial infections in humans.
How does Dr. Moalem assess the power that bacteria have over humans when it comes to bacterial infections such as Chorea and Malaria? How can humans stop these diseases from becoming so widespread and possibly end them once and for all?
Andrew Komarov
a_komarov@comcast.net or akomaro4@students.d125.org
Response #2: 4/7/13
ReplyDeleteDr. Moalem discusses the power that bacteria have over humans in disease such as malaria and cholera basing it on the basic principal that “every infections agent has the same goal¬–to survive and reproduce by infecting new hosts”. He talks about the three main ways that a microbe moves from one host to another: transmission through contact or the air; riding an intermediate organism; and traveling through contaminated food or water. (pg 118)
Specifically, malaria utilizes an intermediate organism to spread the disease. In this case, malaria uses mosquitoes to find and infect new hosts. Malaria has evolved to push its human host to the brink of death. Dr. Moalem states that there is an “evolutionary advantage” to incapacitate humans. The malaria parasite can be transferred from their mosquito host to the human host when the mosquito bites a human. If humans are immobile, they are more vulnerable to attack by mosquitoes. This is advantageous to the malaria parasite because the more able their mosquito hosts are to infect humans, the greater amount of malaria parasites in the human’s blood. Furthermore, if there is a great concentration of the infectious agent in the human’s blood, then when a different mosquito bites the infected human, the mosquito is more likely to pick up the malaria parasite when it consumes the human’s infected blood. In turn, helping malaria to spread to more and more people. (pg 119) This relates to Big Idea #1 in that malaria has evolved to what it is now in finding that a selective advantage for them to survive and reproduce was to immobilize their humans and not rely on human-to-human interaction to spread.
Similarly, cholera does not rely on humans moving for it to spread and infect new people. Cholera moves through unprotected water systems. Again, the disease has evolved to manipulate humans by causing severe diarrhea. A plethora of copies of the cholera disease can travel through the diarrhea in the water supply and end up infecting many other hosts if the water supply is unprotected or poorly treated. (pg 111)
Ewald proposes that by controlling the environment that deadly diseases such as malaria and cholera are spread through, humans (the hosts) can manipulate the bacteria to evolve towards “a less harmful incarnation”. (121) If we protect our water supplies, or contain those infected with malaria, we affect the modes of the parasites movement from one person to another. The disease would theoretically be forced to evolve into a less violent form of itself and rely on humans to be mobile to transfer to a new host. However, Ewald knows that this may not always be applicable. In an article from CNN’s magazine Fortune titled “How Disease Evolves”, Ewald explains his theory in how we can stop bacteria through antibiotics. We have studied how antibiotics may select for the mutant, antibiotic-resistant bacteria in humans. So, Ewald proposes that we “administer antibiotics to infected people only long enough to let their immune systems kick in and knock out the culprits.” In both of Ewald’s proposals, humans can either lessen the spread or the severity or both of these infectious diseases.
http://money.cnn.com/magazines/fortune/fortune_archive/2005/05/16/8260178/
Rachel Chang (rchang4@students.d125.org)