INTEGBI 169 Chapter Notes - Chapter 10: Microorganism, Mary Mallon, 1918 Flu Pandemic
5 Jun 2018
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○ After C. tetani bacteria enter a human wound, the bacteria may grow and divide
rapidly, even though the human body is not their normal habitat; soil is its
normal habitat.
○ While dividing, C. tetani produce a neurotoxin that is lethal to humans.
○ But it is selection in the bacterium's normal life cycle in the soil that leads it to
produce this toxin, not any evolution with a human host.
○ The bacterium finds itself inside a human instead of in the soil by mere
happenstance.
○ Ebola virus -
■ highly virulent organism that acts quickly and has a high mortality rate in
humans
■ Viral infections like Ebola are highly virulent in humans, with short
incubation rates, rapid morbidity, and high mortality.
■ Since most human hosts with Ebola die quickly, this limits the ability for
these human hosts to transmit the infection to a large number of
humans.
■ Ebola also infects certain primate species who have significant morbidity
and mortality from this virus.
■ Some species of bats remain asymptomatic and can be chronic carriers
of Ebola virus
■ It appears that Ebola evolved in bats and persists in the ecosystem in
bats
■ Ebola infection in humans appears to be an example of the coincidental
evolution hypothesis since this virus appears to have co-evolved a host-
pathogen relationship with bats.
■ Humans appear to be a coincidental host for Ebola virus.
○ West Nile virus
■ Flavivirus virus, vector borne infection, originated in Africa.
■ The vector is the Culex mosquito
■ West Nile Virus co-evolved with birds and birds are its primary hosts.
■ The vector Culex can also bite and infect many other vertebrate species.
■ Humans may be a coincidental host of West Nile virus.
■ Approximately 80% of human infections with West Nile virus are
asymptomatic.
●
Short-Sighted Evolution Hypothesis:
Document Summary
After c. tetani bacteria enter a human wound, the bacteria may grow and divide rapidly, even though the human body is not their normal habitat; soil is its normal habitat. While dividing, c. tetani produce a neurotoxin that is lethal to humans. But it is selection in the bacterium"s normal life cycle in the soil that leads it to produce this toxin, not any evolution with a human host. The bacterium finds itself inside a human instead of in the soil by mere happenstance. Highly virulent organism that acts quickly and has a high mortality rate in humans. Viral infections like ebola are highly virulent in humans, with short incubation rates, rapid morbidity, and high mortality. Since most human hosts with ebola die quickly, this limits the ability for these human hosts to transmit the infection to a large number of humans. Ebola also infects certain primate species who have significant morbidity and mortality from this virus.
