Difference between revisions of "Large Strongyles"
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(Created page with '=== Large strongyles === ==== Morphology ==== '''Gross''' *Stout worms, 1.5-5cm long *Large buccal capsule *Bursa visible to the naked eye (male worms only) '''Mi…') |
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| Line 17: | Line 17: | ||
'''Adult Worms''': | '''Adult Worms''': | ||
*Plug feeders | *Plug feeders | ||
| − | *''Strongylus'' species: | + | *''[[Strongylus]]'' species: |
**Large buccal capsule | **Large buccal capsule | ||
**Penetrate right down to the muscularis layer and blood vessels | **Penetrate right down to the muscularis layer and blood vessels | ||
**Leaves small circular bleeding ulcers → anaemia if present in large numbers | **Leaves small circular bleeding ulcers → anaemia if present in large numbers | ||
| − | *''Triodontophorus'': | + | *''[[Triodontophorus]]'': |
**Smaller buccal capsule | **Smaller buccal capsule | ||
**More superficial damage | **More superficial damage | ||
Revision as of 20:08, 26 April 2010
Large strongyles
Morphology
Gross
- Stout worms, 1.5-5cm long
- Large buccal capsule
- Bursa visible to the naked eye (male worms only)
Microscopic (buccal capsule)
- Double row of leaf crowns
- Teeth (0, 2, 3 or more)
- Dorsal gutter (channel for secretions)
Life-cycle
Infection with all three Strongylus species and Triodontophorus is by ingestion of infective stage larvae (L3) at grazing. Larvae pass down the intestinal tract and penetrate the intestinal mucosa at which point there are important species differences in life-cycle.
Pathogenicity
Adult Worms:
- Plug feeders
- Strongylus species:
- Large buccal capsule
- Penetrate right down to the muscularis layer and blood vessels
- Leaves small circular bleeding ulcers → anaemia if present in large numbers
- Triodontophorus:
- Smaller buccal capsule
- More superficial damage
- May feed in "herds", leaving large ulcers, several centimetres across
- Ulcers heal and leave scars
Pathogenesis of infection with Strongylus species larvae:
- S. vulgaris:
- Potentially highly pathogenic
- Damage to cranial mesenteric artery → endarteritis → thrombosis and possibly embolism → colic
- Other Strongylus species :
- Relatively non-pathogenic
- Migration of S. edentatus and S. equinus confined to roomy tissues (e.g. mesentery, liver)
Verminous endarteritis
- Caused by larvae of S. vulgaris within the cranial mesenteric artery
- Also called "verminous aneurism" (misnomer as aneurism = dilatation/thinning of blood vessel wall; also, aneurisms are rare)
- Wall of artery grossly thickened (organising thrombi, inflammatory responses)
- Can be detected on rectal palpation
- Many cases asymptomatic
- May get embolism → infarction of areas of intestinal wall → colic or chronic ulceration (note: generally good collateral circulation; therefore colic is not inevitable)
- Aberrant larvae may cause thrombosis in other arteries; e.g. iliac, cerebral, coronary
- Avermectin/milbemycins or fenbendazole are used to control migrating S. vulgaris larvae