ECOL Parasitism & Diseases

Question 1

Ectoparasites

Answer 1

live on the outside of organisms
-mistletoe, tick, flea

Question 2

Endoparasites

Answer 2

live on the insides of organisms
-ex. COVID-19, helminth

Question 3

Advantages of ectoparasites

Answer 3

-easily move between hosts
-not exposed to host immune system

Question 4

Disadvantages of ectoparasites

Answer 4

-exposed to the environment
-exposed to predators and parasites

Question 5

What are the two ways endoparasites can be?

Answer 5

intracellular: viruses that live and replicate inside host cell
extracellular: intestinal worms, that live and replicate between host cells

Question 6

Advantages of endoparasites

Answer 6

-safe from external environment
-hosts rarely have internal, physical defenses to prevent feeding

Question 7

Disadvantages of endoparasites

Answer 7

-exposed to the host immune system
-hard to move between hosts

Question 8

New parasites and pathogens, known as emerging infectious diseases, can…

Answer 8

evolve through random mutations, which can allow a pathogen to jump to a new host species or become a more virulent strain

Question 9

Zoonotic diseases

Answer 9

jump from non-human animals to humans and are the main source of emerging infectious diseases in humans resulting in many epidemics

Question 10

What are zoonotic epidemics related to?

Answer 10

habitat fragmentation
deforestation
climate change
etc.

Question 11

What model is the simplest way to model the transmission of an infections disease that incorporates immunity of the host?

Answer 11

the S-I-R model

Question 12

What is the S-I-R model?

Answer 12

• 100% of individuals begin as SUSCEPTIBLE TO THE PATHOGEN (S)
• of susceptible individuals, some percentage become INFECTED (I)
• of the infected individuals, some percentage develop RESISTANCE VIA IMMUNITY (R)

Question 13

What is the formula used with SIR Models?

Answer 13

dI/dt = BSI - Ig

Question 14

In the formula:
dI/dt = BSI - Ig

What does BSI stand for?

Answer 14

gains to the infected class

depends on the average number of susceptible individuals infected by one infectious individual per unit time (transmission rate, B), the number of susceptible hosts (S), and the number of currently infected hosts (I)

Question 15

In the formula:
dI/dt = BSI - Ig

What does Ig stand for?

Answer 15

Losses to the infected class

depends on the average number of infected individuals recovered per unit time (recover rate, g) and the number of currently infected hosts (I)

Question 16

For most endoparasites we don’t count individual parasites, but instead the number of hosts infected with parasites. So what model is used?

Answer 16

Ro

Question 17

What is the Ro model?

Answer 17

the basic reproductive number of an infectious disease

-i.e. # of new hosts who are infected by a single infectious host in an entirely susceptible population

Question 18

What is the Ro formula?

Answer 18

Ro = BN/g

Question 19

If the number of individuals gained by the infected class (BN) is grater than the number of individuals lost form the infected class (g) what happens?

Answer 19

disease spreads

Question 20

Ro > 1

Answer 20

the infection will continue to spread through the population (potential epidemic)

Question 21

Ro < 1