Nematodes

Question 1

What types of worms are these and what is there body structure?

Answer 1

The majority of roundworms 
They have a cylindrical body cavity surrounded by cutile 
- muscular pharynx pumps in food 
- simple nervous system 
- separate sexes

Question 2

Describe the structural differences between male and female nematodes

Answer 2

Male - have 2 chitinous rods (spincules) on their tail for grasping and some have a bursa

Female - some have a vulva flap

Question 3

List the different feeding mechanisms used by nematodes

Answer 3

• closely applied to mucosal surface
• swallow ingesta and/or host secretions
• suck a plug of mucosa into the buccal cavity
• bury heads deep into mucosa + suck blood

Question 4

Describe the nematode general lifecycle

Answer 4

Egg –> L1 –> L2 –> L3 –> L4 –> adult

–> = moult

Question 5

Name the Stronglyes and describe their life cycle

Answer 5

Trichostrongyloidea, Strongylodiea + Hookworms

1. Larvae in host mucosa of stomach/intestine
2. Adults in lumen
3. Eggs are dropped in faeces
4. Infected larvae develop on ground

Question 6

Trichostrongyloidea appearance and life cycle

Answer 6

• most look like short bits of cotton
• L1 + L2 feed on bacteria
• L3 = infective stage: encased in L2 cuticle
• L3 –> L4 –> adult: occurs in gastric glands
• PPP = 3 weeks

Question 7

Strongyloidea appearance and life cycle

Answer 7

• short + stout
• L3 –> L4 –> adult: occurs in LI
• larvae penetrate mucosal wall
• disease occurs when larvae break free
• PPP = 3 weeks - 6+ months

Question 8

Hookworm appearance and lifecycle

Answer 8

• head = complex + bent dorsally
• large buccal cavity with teeth and/or cutting plates
• infection can be via ingestion or skin penetration

Question 9

Metastrongyloidea appearance and lifecycle

Answer 9

• string with a bursa
• general life cycle:
  1. Egg hatches in AT and L1 passed in faeces
  2. L1 eaten by intermediate host (mollusc)
  3. L1 –> L3
  NOTE: if intermediate host is eaten L3 invades new host tissue (parantenic host)
  4. L3 –> adult in final host
  5. Adult migrates to RT to lay eggs
  6. Eggs move up RT to be swallowed

Question 10

Ascaridaidea appearance and lifecycle

Answer 10

• big fleshy worms
• non-bursate
• general life cycle:
  1. Adult lays eggs in SI and are passed in faeces
  2. L1 –> L2 inside egg - infection via ingestion of eggs
  NOTE: the eggs can be ingested directly or via an intermediate host (i.e. Earthworm)
  3. After hatching larvae undergo hepato-tracheal migration