Intro to CAR Parasitology

Question 1

Define parasitism

Answer 1

Only one organism (parasite) benefits from the interaction to the detriment of the other (host)

Question 2

Define mutualism

Answer 2

Organisms of different species both benefit from the interaction e.g. Honey bee & flowering plant

Question 3

Define commensalism

Answer 3

Only one organism benefits from this association without causing harm to the second organism

Question 4

Define hyperparasitism

Answer 4

Parasites of parasites

Question 5

Define parasitoid

Answer 5

Parasites which kill the host at the end of their lifecycle

Question 6

Define symbiosis

Answer 6

A close and prolonged interaction between organisms of different species

Question 7

Define a facultative parasite

Answer 7

May survive in the absence if the host e.g. opportunistic

Question 8

Define a obligate parasite

Answer 8

At some or all stages of life cycle cannot survive without host

Question 9

Define an endo-parasite

Answer 9

Lives inside the host e.g. worms, protozoa

Question 10

Define a ecto-parasite

Answer 10

Lives in/on the outer surfaces of the host e.g. Fleas, lice, tick, mites

Question 11

Define a definitive host

Answer 11

The final host in which parasite sexual reproduction occurs

Question 12

Define an intermediate host

Answer 12

The host in which parasite asexual reproduction occurs

Question 13

Define a permissive host

Answer 13

An accidental host not usually used by parasite but still allows life cycle completion e.g., liver fluke (Fasciola hepatica) infection in humans

Question 14

Define a non-permissive host

Answer 14

An accidental host in which the parasite cannot complete the life cycle. e.g., Toxocara infection in humans

Question 15

Define a reservoir host

Answer 15

Host in which parasites can be maintained AND which is the source of infection for another host that we’re interested in (the ‘target’ host) BUT in parasitology also used to mean simply a large source of the parasite (eg paratenic hosts)

Question 16

Define a paratenic host

Answer 16

Host not necessary for the lifecycle or development, but which can act as a ecological/epidemiological ‘dump’ (‘reservoir’) of the parasite and source of infection e.g. frogs for dog lungworm

Question 17

Explain the principle of a mechanical vector

Answer 17

A vector which mechanically spreads a parasite: no parasite replication occurs so mechanical vectors are not hosts (but may be important to transmission)

Question 18

Explain the principle of a biological vector

Answer 18

An intermediate host which is itself (usually) a parasite

e.g. mosquitoes transmitting malaria

Question 19

Identify the portals of entry for parasites into the animal body

Answer 19

Ingestion (eg in food or water)

Skin penetration (eg hookworm larvae)

Skin inoculation by arthropod bite (‘vector’-borne protozoa)

Direct animal-to-animal contact (lice)

Trans-placental (vertical) (Strongyloides spp)

Sexual intercourse (Trichomonas spp)

Inhalation (Cytodites spp airsac mites in birds, Pneumonyssus spp pulmonary mites in primates)

Question 20

Define a direct lifestyle of a parasite

Answer 20

Parasitic stages develope in/on host

E.g cattle lungworm

Question 21

Define an indirect lifestyle of a parasite

Answer 21

Intermediate host(s) (different species) needed for the development of some stages of the parasite

E.g. Canine lungworm

Question 22

What questions would be asked, during a diagnosis, to understand a parasites life cycle?

Answer 22

• Type of life cycle (direct or indirect)
  • What’s the definitive host?
  • What are the intermediate host? (if any, then it is indirect cycle)
  • What is the infective stage to the host your are interested in?
  • What are the routes of infection?

Question 23

How does understanding a parasites life cycle help during diagnosis and treatment?

Answer 23

Help to understand pathology, clinical signs and diagnosis

Enable us to:
Determine an appropriate therapeutic ‘window’

Manage disease properly

Protect other animals from cross-infection

Protect people from zoonotic infections

Question 24

Understand the basis of cardio-respiratory parasite control

Answer 24

Integrated parasite control

-Avoiding risky behaviour

-Hygiene & nutrition means good immune response to reduce risk

-Disrupting transmission ( treating intermediate hosts / not letting the animal eat faeces / washing toys)

-Treatment intervention (few vaccines for this area / drugs can lead to resistance and damage the non targeted species in the environment (poor environmental effects)

Question 25

Give examples of parasitic phyla

Answer 25

nemathelminths

Question 26

Understand the morphological features of round worms

Answer 26

‘Helminth’ is a general (rather than biological/taxonomic) term for endoparasitic ‘worms’ and worm-like creatures:

- Nematodes – (nematos = thread)

- Acathocephala – (akanthos = thorn)

- Platyhelminthes (platy = flat)
	○ Cestodes – tapeworms
	○ Trematodes – flukes
            (monogeneans are ectoparasitic flatworms of fish)