5c: Transmission and virulence

Question 1

Transmission definition

Answer 1

Transmission is the spread of a parasite to a host

Question 2

Virulence definition

Answer 2

Virulence is the harm caused to a host species by a parasite

Question 3

Ectoparasites are generally transmitted through…

Answer 3

direct contact or by consumption of intermediate hosts

Question 4

How are endoparasites of body tissues transmitted

Answer 4

Endoparasites of the body tissues are often transmitted by vectors

Question 5

Factors that increase transmission rates:

(Of parasite spread)

Answer 5

• the overcrowding of hosts when they are at high density
• mechanisms, such as vectors and waterborne dispersal stages, that allow the
  parasite to spread even if infected hosts are incapacitated

Question 6

Host behaviour is often exploited and modified by parasites to maximise transmission by

Answer 6

Alteration of host:
- foraging
- movement
- sexual behaviour
- habitat choice
- antipredator behaviour.

Host behaviour becomes part of the extended phenotype of the parasite

Question 7

How does a parasite exploit the host to benefit parasite growth, reproduction or transmission

Answer 7

• suppress the host immune system
• modify host size and reproductive rate

(in ways which benefit parasite growth, reproduction and transmission)