Lec 1. Intro to Parasitism

Question 1

A parasite that is impacting the Canadian arctic is called _____. You can get it from eating raw meat. It’s usually not a concern because of government regulations, but it’s very prevalent in the north

Answer 1

trichinosis

Question 2

Traditional indigenous tea from Canadian Arctic made from rhododendron leaves could combat drug-resistant _____

Answer 2

malaria

Question 3

Parasitic relationship=

Answer 3

a symbiotic relationship in which one partner (parasite) has a trophic relationship with the other partner (host)

Question 4

Each parasite life cycle stage typically in ___ host(s)

Answer 4

one host per life cycle stage
- different life stages can affect different hosts

Question 5

T/F

The parasite can let its host live, but often kills it

Answer 5

false

parasite often harms, but rarely kills the host. The host can’t benefit them if it’s dead!

Question 6

The objective of parasites is to ___

Answer 6

reproduce

Question 7

List 4 of the main forms of parasitism

Are these categories mutually exclusive?

Answer 7

• Typical parasite
• Trophically transmitted parasite
• parasitic castrator
• parasitoid

Not mutually exclusive, one parasite can fall under more than one of these categories

Question 8

Typical parasite=

Answer 8

• transmission does not require host death (may accidentally cause death)
• host can usually still reproduce

Question 9

Trophically transmitted parasite=

Answer 9

• transmission requires host death (eg. predator-prey interaction)
• parasite rarely kills host directly

Question 10

Parasitic castrator

Answer 10

• some typical or trophically-transmitted parasites castrate their host.
• consume so much of the host’s tissue that the host becomes infertile (some parasites use chemicals)

Question 11

What might be the purpose of a parasite castrating their host?

Answer 11

Then the host doesn’t put energy towards reproduction, so resources are put towards body maintenance, which benefits the parasite

Question 12

Parasitoid=

Answer 12

Transmission requires parasite to kill host directly

Question 13

Describe trophically-transmitted parasites

Answer 13

Parasites that infect each trophic level as it passes through (eg from producer to top predator)

Often different hosts= different life stages of the parasite

Question 14

Give an example of a trophically-transmitted parasite

Answer 14

a typical trematode

Question 15

Obligate parasite=

Answer 15

An organism that MUST be parasitic at some point in its life

Question 16

Facultative/ opportunistic parasite=

Answer 16

An organism that can either be parasitic or free-living
- depends on conditions (host/ enviro)

Question 17

Endoparasite=

Answer 17

a parasite that lives inside the host

Question 18

Ectoparasite=

Answer 18

a parasite that lives outside the host

eg. lice/ ticks

Question 19

Hyperparasites

Answer 19

parasites of parasites

Question 20

If a parasite has a direct life cycle, how many hosts does it have?

Answer 20

1

Question 21

If a parasite has an indirect/ complex life cycle, how many hosts does it have? Describe what happens in the host(s)

Answer 21

Two or more hosts are required.

• 1 definitive host: this is where the parasite grows, matures, & reproduces
• 1 or more intermediate hosts: parasite might asexually reproduce here, or just grow

Question 22

Definitive host=

Answer 22

A host required for the development of a sexually mature (adult) parasite

Sexual reproduction happens in the definitive host

Question 23

Intermediate host=

Answer 23

A host required for a larval parasite to develop into the next stage

Question 24

Vector=

Answer 24

blood feeding invertebrate host
eg. mosquito

Can be intermediate (usually) or definitive)

Question 25

For Malaria, is the mosquito or the human the definitive host?

Answer 25

The mosquito! Because that’s where sexual reproduction happens

Question 26

Reservoir hosts=

Answer 26

an animal that is infected by a parasite & serves as a source of infection for humans (zoonoses).

= host in which parasites can mature & reproduce –> helps maintain the parasite when no normal hosts are available

Question 27

Paratenic hosts=

Answer 27

hosts in which parasite development does not occur
–> no parasite development, just a transport

• may bridge ecological/ trophic gap in parasite’s life cycle

Question 28

Prevalence=

Answer 28

proportion of hosts examined that are infected

PrevALence= ALL cases/ population @ risk

Question 29

Incidence=

Answer 29

Number of new occurrences of a disease in a population

iNcidence= New cases/ Pop @ risk

Question 30

Intensity=

Answer 30

Number of parasites per infected host

= total # of parasites/ # infected hosts

Question 31

Abundance=

Answer 31

number of parasites per host that was examined

= total # of parasites/ All hosts examined

Question 32

Density=

Answer 32

number of parasites per unit of host tissue

eg. 20 parasites per liver tissue

eg. Parasitemia

Question 33

How can we measure density when parasites are not easily counted?

Answer 33

Parasitemia!

% parasitemia= (parasitized RBCs/ total RBCs) x100%

Question 34

Explain the difference bewteen intensity & abundance

Answer 34

Intensity= how bad the infection is within each host (average)
Abundance= an estimate of what’s going on in the whole population

Question 35

A parasite has a mean density of 2. What does that mean?

Answer 35

If you get this parasite, you’ll probably get 2 of them (average)