On page 105-107, Dr. Moalem discusses the parasite Toxoplasma Gondii or T. gondii. The parasite reproduces by asexual reproduction during the life of its host. T. gondii is a host manipulator parasite, meaning the parasite
manipulates the host (in this case mice and rats) and can get the host to
do whatever the parasite wants. When T. gondii get into a mouse
via cat droppings, the parasite moves into the muscle and brain cells of
the mouse.The mouse then becomes fat and lethargic. The mouse loses the
fear of cats and is attracted to the smell of cats. A slow mouse
attracted to cats means cat food for the cat which is exactly what the T. gondii want because T. gondii can only sexually reproduce in cats.
This question is related to Big Idea 3 (living systems store, retrieve,
transmit, and respond to information essential to life processes) as
the mice respond to the information from the T. gondii, even though the information is wrong. When the parasite is in a cat, the parasite produces new oocysts. The oocysts are then excreted from the cat as feces and other animals, including humans, can ingest the oocysts. Ingesting the oocysts causes the animals to become infected since the T. gondii cells are distributed throughout the body by the bloodstream and the T. gondii get inserted inside muscle and brain cells.
Humans can be infected by this parasite by consuming raw meat or
handling cat litter. Dr. Moalem mentions that there is increasing
evidence that a past infection by T. gondii may trigger
schizophrenia in some humans. Schizophrenia is a brain disorder in which
patients can be delusional, have hallucinations, disorganized behavior,
and more. What T. gondii actually does to the brain is still unclear and whether or not T. gondii causes schizophrenia is also unclear. However, a study conducted by researchers at Johns Hopkins University has shown that mice infected with T. gondii may be helped with antipsychotic medications.
Research
another manipulative parasite that may cause certain diseases in humans
and explain how the behavior of the parasite can cause the symptoms of
the disease. Explain the selective advantage of the manipulation performed by the parasite on the parasite's host. Then
discuss whether or not treatments of the disease potentially caused by
the parasite might help with treatment of patients infected with the
parasite.
(Laura Gu, laugu4@students.d125.org)
Another manipulative parasite is the deer tick. Deer ticks are often carriers of Lyme disease, caused by the bacterium Borrelia burgdorferi. Tick bites are fairly common. Deer ticks bite humans so they can feed and if they transmit Lyme disease, the infection starts at the bite and causes a localized bulls eye rash.
ReplyDeleteWhen the deer tick bites a human, the spirochete is preceded by tick saliva. Tick saliva contains chemicals that halt an immune response, thus allowing the bacteria to survive. The lack of an immune response is advantageous to the bacteria because they can survive in a localized area, then multiply and spread to the rest of the body. Unlike the parasite, T. gondii, mentioned on p 105-107, deer ticks do not directly produce any physcological effects on the host.
The treatment for the disease includes antibiotics. Antibiotics only affect the Borrelia burgdorferi, not the deer tick that transmitted the disease. Deer ticks have to be physically removed, or they fall off the human after feeding.
Information about Lyme disease:
Pathophysiology of the Lyme Disease Spirochete, Borrelia burgdorferi, in Ixodid Ticks
Willy Burgdorfer, Stanley F. Hayes and Dan Corwin
Reviews of Infectious Diseases , Vol. 11, Supplement 6. Lyme Disease and Other Spirochetal Diseases (Sep. - Oct., 1989), pp. S1442-S1450
(Katelyn Noronha, knoronh4@students.d125.org)