Strongylida 1

Question 1

phylum Nematoda general characteristics?

Answer 1

• body a long thin tube
• exoskeleton- cuticle
• plus a hydrostatic skeleton + muscle allows for locomotion
• straight gut with highly variable pharynx
• sexes are separate

Question 2

what do Phylum Nematoda morphological elaborations allow them to do?

Answer 2

Nematoda to be concentrated around openings

• mouth
• excretory ducts
• gonadal openings

Question 3

Basic Nematoda development

Answer 3

• Typically egg, L1, L2, L3, L4, Adult
• L1 + L2 usually free living
• L3 = infective, transitional stage
• L4 (preadult) = migratory in definitive host
• Adult

Question 4

Orders of bursae nematodes?

Answer 4

• Order = Strongylida

Question 5

Non-bursate nematodes orders (6)

Answer 5

Rhabditoidea - strongylodies
Ascarididoidea - ascarids
oxyuroidea - pinworms
Trichinelloidea - Trichinella
Habronematoidea
filarioidea - filariids

Question 6

General information of the order strongylida?

Answer 6

(bursate nematodes)
most important and diverse group of parasitic nematodes
parasites of Gi Tract or lungs
only males have bursa

Question 7

what is a bursa?

Answer 7

– Fan-like structure at posterior end, grasps female for copulation
– Bursal rays of taxonomic significance

Question 8

Ancylostomatoidea, general characteristics?

Answer 8

• Hook worms
• Buccal capsule well developed
• Buccal capsule bent dorsally
• Teeth or cutting plates at mouth opening
• Adults in small intestines, carnivores, ruminants

Question 9

Strongyloidea, general characteristics

Answer 9

• buccal capsule well developed
• buccal capsule not bent or ventrally
• leaf crowns usually present
• Adults of most occur in large intestines and/or caecum
• Adults in L1 of horses, ruminants

Question 10

Trichostrongyloidea, general characteristics

Answer 10

• Buccal capsule vestigial
• Bursa well developed
• Leaf crowns usually absent (may be extremely reduced)
• Adults in upper GIT (Abomasum/stomach or small intestine) All herbivores (common), one in cats

Question 11

Metastrongyloidea, general characteristics?

Answer 11

• buccal capsule vestigial
• bursa vestigial
• adults in lungs/pulmonary vasculature
• cattle, cats, rats (rat worm or minor veterinary and public health significance)

Question 12

life cycle of strongylids

Answer 12

• simplest life cycle seen in superfamily trichostrongyloidea
• egg in faeces
• L1 in faeces
• after two moults develops into L3
• L3 escapes faeces, migrates in environment
• L3 is eaten
• L4 in small intestine (sometimes penetrate mucosa)
• Adult worms in Gi tract of host

Question 13

Trichostrongyle life cycle?

Answer 13

• eggs pass in faeces
• embryonate in faeces (24hrs)
• After 2 moults L3 moves into surrounding soil, escaping the faeces
• L4 usually enter the mucosal lining of the host

Question 14

Trichostrongyle eggs embryonate based on what factors? (3)

Answer 14

• moisture
• oxygen
• heat

Question 15

Explain the trichostrongyles tissue stage?

Answer 15

• usually this is L4
• entering the mucosal lining of the host
• after there is no further tissue migration
• emerge after a few days as adults
• adults in intestine or stomach

Question 16

Explain egg development of nematodes in faecal mass at day 0

Answer 16

Faecal mass

• moist/liquid consistency
• 75% of bacteria alive
• oxygenated at the surface

Eggs

• Scattered throughout mass
• embryonate
• 95% die to anoxia
• 5% hatch

Question 17

Explain egg development of nematodes in faecal mass at day 1

Answer 17

Faecal mass

• Moist
• Crust forms- retains. moisture internally

Larvae

• hatch
• remain in moist inner layers
• feed on bacteria and moult

Question 18

Explain egg development of nematodes in faecal mass at day 7

Answer 18

Faeces

• moist internally
• crust externally
• when rain occurs it allows larval escape

Larvae
- infective 3rd stage escapes if sufficient moisture

Question 19

Explain egg development of nematodes in faecal mass, the importance of “Thin film of moisture”.

Answer 19

• <0.5mm

- allows larvae to crawl to the tops of grass

Question 20

Explain the larvae movement and when they die and distance moved by larvae

Answer 20

• cannot move if no moisture
• most die in 4 weeks in the pasture
• distance travel is mostly under 30cm

Question 21

What is Pilobolus?

Answer 21

• a fungus which when swollen, it fires things 6ft high - 8ft away
• parasites nematode hitchhikers

Question 22

larval dynamic when there is a drought

Answer 22

• larvae become sealed in faeces and stop development
• larvae can survive in faces for 5-6months
• in droughts number of pats increase - lots of faecal matter with eggs
• larvae emerge after rain 50mm/48hrs (larval bursts)

Question 23

larval dynamics in winter

Answer 23

• larvae stop development in faeces
• emerge at increased temp and increased moisture in spring
• pats accumulate on pasture then emerge at spring

Question 24

larval dynamics in hot summers

Answer 24

high temp are lethal to pats and on pasture

Question 25

Cattle vs sheep trichostrongyles

Answer 25

Cattle

• large masses, small SA/V
• stay moist for linger
• L3’s tend to survive dry pats better
• Larvae climb up 10cm up grass blade (because cattle feed at tops of grass)

Sheep

• Pellets, large SA/V
• Evaporation higher
• L1/egg tend to survive drying of pats better

Question 26

What is hypobiosis? Explain it’s relation with trichostrongyles.

Answer 26

• Arrested/inhibited development
• lots of trichostrongyles larvae developing mucosa of gastro-intestinal tract of host do into period of arrest
• reasoning = probably complex (but may relate principally to helping worms over-winter or summer, nematode density (adults have inhibitory effect, immunity)

Question 27

example of Ostertagia in cattle

Answer 27

Osteragia ostertagi - small brown stomach worm found

in cattle throughout Australia

Question 28

Explain the amount of larvae in pastures based on the seasons?
when is highest infection rate of trichostrongyle?
What occurs to larvae infecting cattle during spring?

Answer 28

• hot dry summer = few larvae on pasture
• autumn and winter = larvae accumulating in pats (thus increase in larvae in pats)
• highest infection rates are in late winter and spring. Larvae survive less on pasture as summer approaches

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