Strongylida 1 Flashcards
phylum Nematoda general characteristics?
- body a long thin tube
- exoskeleton- cuticle
- plus a hydrostatic skeleton + muscle allows for locomotion
- straight gut with highly variable pharynx
- sexes are separate
what do Phylum Nematoda morphological elaborations allow them to do?
Nematoda to be concentrated around openings
- mouth
- excretory ducts
- gonadal openings
Basic Nematoda development
- Typically egg, L1, L2, L3, L4, Adult
- L1 + L2 usually free living
- L3 = infective, transitional stage
- L4 (preadult) = migratory in definitive host
- Adult
Orders of bursae nematodes?
- Order = Strongylida
Non-bursate nematodes orders (6)
Rhabditoidea - strongylodies Ascarididoidea - ascarids oxyuroidea - pinworms Trichinelloidea - Trichinella Habronematoidea filarioidea - filariids
General information of the order strongylida?
(bursate nematodes)
most important and diverse group of parasitic nematodes
parasites of Gi Tract or lungs
only males have bursa
what is a bursa?
– Fan-like structure at posterior end, grasps female for copulation
– Bursal rays of taxonomic significance
Ancylostomatoidea, general characteristics?
- Hook worms
- Buccal capsule well developed
- Buccal capsule bent dorsally
- Teeth or cutting plates at mouth opening
- Adults in small intestines, carnivores, ruminants
Strongyloidea, general characteristics
- 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
Trichostrongyloidea, general characteristics
- 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
Metastrongyloidea, general characteristics?
- buccal capsule vestigial
- bursa vestigial
- adults in lungs/pulmonary vasculature
- cattle, cats, rats (rat worm or minor veterinary and public health significance)
life cycle of strongylids
- 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
Trichostrongyle life cycle?
- 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
Trichostrongyle eggs embryonate based on what factors? (3)
- moisture
- oxygen
- heat
Explain the trichostrongyles tissue stage?
- 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
Explain egg development of nematodes in faecal mass at day 0
Faecal mass
- moist/liquid consistency
- 75% of bacteria alive
- oxygenated at the surface
Eggs
- Scattered throughout mass
- embryonate
- 95% die to anoxia
- 5% hatch
Explain egg development of nematodes in faecal mass at day 1
Faecal mass
- Moist
- Crust forms- retains. moisture internally
Larvae
- hatch
- remain in moist inner layers
- feed on bacteria and moult
Explain egg development of nematodes in faecal mass at day 7
Faeces
- moist internally
- crust externally
- when rain occurs it allows larval escape
Larvae
- infective 3rd stage escapes if sufficient moisture
Explain egg development of nematodes in faecal mass, the importance of “Thin film of moisture”.
- <0.5mm
- allows larvae to crawl to the tops of grass
Explain the larvae movement and when they die and distance moved by larvae
- cannot move if no moisture
- most die in 4 weeks in the pasture
- distance travel is mostly under 30cm
What is Pilobolus?
- a fungus which when swollen, it fires things 6ft high - 8ft away
- parasites nematode hitchhikers
larval dynamic when there is a drought
- 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)
larval dynamics in winter
- larvae stop development in faeces
- emerge at increased temp and increased moisture in spring
- pats accumulate on pasture then emerge at spring
larval dynamics in hot summers
high temp are lethal to pats and on pasture
Cattle vs sheep trichostrongyles
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
What is hypobiosis? Explain it’s relation with trichostrongyles.
- 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)
example of Ostertagia in cattle
Osteragia ostertagi - small brown stomach worm found
in cattle throughout Australia
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?
- 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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