Intro to Parasitology

Question 1

What is the definition of a parasite?

Answer 1

An organism that lives on or in a host organism, they feed grow and multiply in a way that can harm their host.

Question 2

Why are parasites important in verterinary medecine? (what may they cause?)

Answer 2

Death

Overt clinical disease

Sub-clinical disease ‘less than optimum productivity’

Question 3

What is ‘Less than optinum productivity’ (LOP)?

Answer 3

Failure of a animal to reach its full genetic potential because of sub-clinical parasitism e.g. poor weight gain.

Question 4

What are the 3 main parasite groups/classifications?

Answer 4

Helminths
Arthropods
Protozoa

Question 5

What are some of the properties of a nematode (roundworm)?

Answer 5

Cylindrical shape
Long (>50cm long)
Tough elastic cuticle
Basic nervous system
Muscle cells for movement
Seperate sexes

Question 6

Why do male roundworms have a bursa?

Answer 6

Grasping onto the body of the female during copulation.

Question 7

What are some of nematodes feeding behaviours?

Answer 7

Have a muscular pharync and oesophagus
Some worms swallow gut ingesta and/or host secretions
Others suck a plug or mucosa into their buccal cavity (or mouth; plug feeders)
Some buty their heads deep into the mucosa and suck blood

Question 8

What is the life cycle of a nematode?

Answer 8

Egg produced from adult
There are 4 larval stages of growth
After the 4th the worm becomes an fully grown adult

Question 9

What are some of the morphological features of a Cestodes/tapeworm?

Answer 9

Tape-like body (strobila), made up of segment (proglottids)

Each segments has 1 or more sets of male and female reproductive organs

Head (Scolex) has suckers/hooks which are used to attach to the inside of the intestines of thier host

Proglottids mature as they pass down the chain

Mature (gavid) segments drop off adult tapeworm daily

Eggs immediately infective (contains tapeworm larva)

Question 10

What is the feeding behaviour of cestodes?

Answer 10

Usually live in the host small intestine
Tapeworm have no digestive tract
Absorb nutrients across bosy surface covered by a tegument (many minute projections, ‘microthreces’)

Question 11

What is the purpose of microthreces in cestodes?

Answer 11

Increase the surface area of the teguments for enhanced absorption of nutrients

Question 12

Give an example of a tapeworm and describe its life cycle.

Answer 12

Taenia solium (pork tapeworm)

Eggs are eaten by pig (intermediate host)
Larvae hatch and migrate from gut to muscle in the pig
Larvae form cysts in the pigs muscles (metacestode stage)
Human eats cysts in undercooked meat
Eggs passed in faeces

Humans are the final host

Question 13

What happens if the human eats tapeworm eggs?

Answer 13

Cysts develop in the brain, in this case the human can become the intermediate host

Question 14

What is the most common route of transmission for tapeworms?

Answer 14

Eating raw/undercooked tissues infected with tapeworm cycsts/larvae

Question 15

What is the difference between a cysticercus, coenurus, and hydatid cyst?

Answer 15

Cysticercus: contain one scolex
Coenurus: contain many scolices
Hyatid cyst: contains thousands of scolices

Question 16

What are some of the morphological features of trematodes ‘flukes’?

Answer 16

Flat, leaf-like worms
Oral and ventral suckers
Mouth leads from oral sucker to blind ending caecae
Most species hermaphrodite, but individuals cross-fertilize
Flukes covers by a metabolically highly active tegument important role in evasion of host immune response

Question 17

What are the feeding behaviours of trematodes?

Answer 17

Flukes live in the digestive system, liver (bile ducts) or blood vessels
Suck blood/ingest tissue deris (pumped into caecae

Question 18

Describe the life cycle of trematodes? flatworm/flukes

Answer 18

EGG–> Miracidium—> inside snail—>Sporocyst—>outside snail—>cercaria—>metacercaria—>inside sheep/adult animal—>adult fluke

Question 19

How do the trematodes multiply?

Answer 19

Asexually inside the snail, one egg=hundreds of adults

Question 20

What are some of the morphological features of arthropods?

Answer 20

Great diversity
Seperate sexes
Insects: 3 body divisions, compound eyes, 3 pairs of legs, may have wings.
Acarina: 2 body divisions, simple eyes, 4 paris of legs, no wings

Question 21

What are the feeding behaviours of arthropods?

Answer 21

Mouthparts show a variety of adaptations:
Sucking up liquified food
Sucking blood
Chewing skin debris
Not feeding at all

Question 22

What are the 3 different life cycles in arthropods and describe them in short term?

Answer 22

Simple metamorphosis: lice
EGG–>NYMPH—>ADULT

Complex metamorphosis: Fleas, flies
EGGS—>LARVAE—>PUPAE—>ADULT

Acarina: same for mites and ticks
EGGS—>LARVAE—>NYMPHS—>ADULTS

Question 23

What are some of the morphological features of Protozoa parasites?

Answer 23

Great diversity
Unicellular organisms-always compromise of just one cell
Eukaryotic (have nucleus)
Can be motile (using structures such as cilia, flagella)

Question 24

What are some of the feeding behaviours of protozoa?

Answer 24

No mouth
Take in nutrients via:
Pinocytosis: cell drinking-fluid droplets
Phagocytosis- cell eating-larger particles
Vesicles fuses with lysosome=digestion
Waste excreted through cell membrane

Question 25

Whats the life cycle of a protozoa?

Answer 25

Asexual repro (usually)= Binary fission, multiple fission Both sexual and asexual repro (Apicomplexa group)= gametes produced fuse to frm oocyst

Question 26

Number of hosts required for life cycle varies in protozoa life cycle. Name/describe the 3 types? give example for each.

Answer 26

Homoxenous-use single host=DIRECT life cycle (Coccidia of poultry) Heteroxenous- use more than one host=INDIRECT life cycle (Trypanosoma) Faculatatively Heteroxeneous- may use more than one host (Toxoplasma)