VL23: Evolution of virulence Flashcards
What questions do we have about virulence?
- why are pathogens virulent?
- why are does virulence differ between pathogens?
- Does virulence change over time?
What is the advantage od virulence?
thrive in new environments - evolutionary advantage
has to be connected with transmission, if not: dead
Is there a correlation between infection dose and virulence?
no
How/Why is virulence related to transmission
expect higher virulence with horizontal transmission
expect lower virulence with vertical transmission (parent to child) (has to live long enough to get a child)
Name 3 main hypothesis for virulence evolution
- co-insidental evolution hypothesis
- shortsighted evolution hypothesis
- trade-off hypothesis
What is the Co-incidental evolution hypothesis?
virulence may not be target of selection -> accident
tetanus toxin probably selected for living in soil, virulent in humans
What is the short-sighted evolution hypothesis?
some pathogens live for many generations in a host before transmitting to a new host -> select for within host fitness
(evolution is always short-sighted)
Describe 1 example of short-shighted evolution
kjh
Under which conditions can it be useful for a pathogen to cause harm?
kjh
Estimate virulence rates in e.coli and HIV
e.coli 10^-10 mutation rate (rather similar to human rate)
HIV 10^^-6 high mutation rate, large population, huge variation in 1 patient, some will be better at growing/transmission
What is the trade-off hypothesis?
jkh
Why is HIV1 more common than HIV2?
jhg
Describe the trade-off example Myxoma virus
kjh
Describe an experimental test of virulence evolution?
jn
How was the experimental set-up and how were results measured?
kjh
