2.5c - Transmission and Virulence

Question 1

Transmission is…

Answer 1

the spread of a parasite to a host

Question 2

Virulence is…

Answer 2

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

Endoparasites of the body tissues are often transmitted by…

Answer 4

vectors

Question 5

Factors that increase transmission rates:

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 the infected hosts are incapacitated
• host behaviour is often exploited and modified by parasites to maximise transmission - alteration of host foraging, movement, sexual behaviour, habitat choice or anti-predator behaviour, the host behaviour becomes part of the extended phenotype of the parasite
• parasites often suppress the host immune system and modify host size and reproductive rate in ways that benefit the parasite growth, reproduction or transmission