On pages 106-108, Dr. Moalem discusses the parasite Toxoplasma gondii, and the parasite’s
effect on humans compared to mice. T.
gondii reproduces in cats only, so for the parasite to get back to a cat,
it must manipulate a mouse. In mice the parasite nests in the brain and
muscles. With chemicals the parasite turns the mouse lazy and fat. Eventually
the mouse loses it’s fear of predators. The cat sees the mouse and thinks
“dinner”. And that's how the T. gondii gets back into the cat.
But, the effects of T.
gondii are benign in humans, with the exception of HIV patients and
pregnant women. Researchers have found that infection may trigger
schizophrenia, but it’s also likely that people with schizophrenia are more at risk for getting the parasite than healthy people, since they have behaviors like poor
hygiene. The T. gondii infection is
like the “chicken or the egg” situation, does it cause the behaviors? Or do the
behaviors cause the infection?
Relating to Big Idea 4, explain the relationship between
humans and T. gondii and discuss how the parasite manipulates mice and their relationship. Also pick a
side in the “chicken or the egg” situation (infection causes a behavior or the
behavior causes it) and provide evidence to why you think your side is right.
Anna Podber
(apodber3@students.d125.org)
Anna Podber
(apodber3@students.d125.org)
In his book, Dr. Moalem discusses how T. gondii travels up the food chain from mice to humans. T. gondii makes the mouse “fat and lethargic…[losing] its natural fear of predators,” (106) distorting its behavior greatly. A predator bird then eats the mouse, and if a human eats that bird, the T. gondii can enter a person, ending up living in his/her brain. Some scientists believe that if this parasite makes it into a person, it can cause behavioral changes like those that occur in an infected mouse. However, Dr. Moalem says in his book “it is not clear whether T. gondii is causing the behavior or wheher people with these behavioral tendencies are more likely to be exposed,” (108). It is difficult to tell solely from the book if schizophrenia can cause a person to contract T. gondii, because the novel doesn’t tell how many people have this parasite, and how many of those people also have schizophrenia.
ReplyDeleteIn the article “Are ‘Cat Ladies’ More Likely to Attempt Suicide?” published by Time magazine, the article states that T. gondii infected women were associated with an increased risk of suicide. The article states that the T. gondii parasite may cause changes to personality and also a mental illness. However, the same article talks about how 10-20% of America may have it, yet it lies dormant in the majority of the people after the initial infection. A scientist named Jaroslav Flegr believes T. gondii may contribute to car crashes, suicides and schizophrenia.
While this article says that T. gondii messes with a person’s brain chemistry, the degree of the changes is under debate. Some say little change at all happens, while other scientists like Jaroslav think this protozoan has a bigger impact than we think. This relates to the symbiotic relationship of parasitism we discussed in the unit on Ecology and Behavior, because regardless of the degree of damage, this protozoan is hurting us, and humans are gaining nothing from T. gondii in return. This article shows that a lot of people have this parasite in them. Ten percent of the country is not schizophrenic, so that suggests that the infection does not cause a behavior change, at least in the majority of cases. If people who have the parasite have schizophrenia, they must have had it previously, which does suggest that schizophrenics may be more likely to develop the disease. This topic relates to Big Idea 4 because it is showing how an parasite can react differently when inside two different hosts, a mouse and a human.
Sifferlin, Alexandra. "Are ‘Cat Ladies’ More Likely to Attempt Suicide? | TIME.com." Time. Time, 03 July 2012. Web. 10 Apr. 2013.
(Zachary Rane, zrane3@students.d125.org)