Lecture 19

Question 1

Define evolutionary medicine

Answer 1

The application of evolutionary principles to the problems of health (diagnostic, treatment, prevention)

Question 2

Reasons we are vulnerable to disease (3)

Answer 2

Trade offs (structures and systems are strained as they balance conflicting demands)

Environmental change (environment changes faster than selection/evolution can keep up to)

Pathogen evolution (pathogens evolve faster than we do)

Question 3

Define virulence

Answer 3

Additional mortality rate that a pathogen imposes on an infected individual (host)

Question 4

Describe the elements of pathogen virulence Conventional Wisdom (3)

Answer 4

Pathogens rely on host to survive (no beneficial to kill host)

Overtime should have convolution of pathogens + host to a mutualistic association

Instances of highly virulent pathogens must be cases where host-pathogen relationship is recent (not enough time to become benign)

Question 5

Highly virulent, fairly short lived diseases are caused by what kind of events?

Answer 5

Spillover events where the human is not actually the main host of the virus (think: Ebola virus and bat hosts who have an intermediate virulence)

Question 6

Challenges to Conventional Wisdom (2)

Answer 6

Tuberculosis (highly virulent and around for a long time)

Myxoma virus (highly virulent in new rabbit populations, intermediately virulent in exposed populations)

Question 7

The trade off hypothesis (costs and benefits of replication)

Answer 7

Cost of replication: level of virulence is a consequence of pathogen replication in host

Benefit of replication: pathogen replication required for transmission between hosts p

Question 8

Replication of pathogens evolves to maximize what?

Answer 8

Transmission and spread

Question 9

Equation for pathogens maximizing the number of new interactions R(0)

Answer 9

R(0) = T(r) x D(r)

T(r) = # of new infections/day 
D(r) = # of days infection lasts

Question 10

Modes of disease transmission (2) Which tends to be more virulent? Give illness examples for each

Answer 10

Direct host-to-host transmission (hosts must be mobile + functioning to transmit)
- ex. Common cold

Vector transmission (do not have to be mobile)
- ex. Malaria 

The more virulent mode is vector transmission as it has a higher replication rate

Question 11

What is cholera and what efforts are suggested to lower virulence? (2)

Answer 11

Cholera is a highly virulent and fatal disease typically transmitted by water

Efforts to lower virulence:
Provide uncontaminated drinking water
Remove vectors (decrease transmission)