Difference between revisions of "Cyathostomins"

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=== Small strongyles (Cyathostomins) ===
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{{Taxobox
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==== Morphology ====
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|name              =''Cyathostomins
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'''Gross''':
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|kingdom            =
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*Small worms, <1.5cm long
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|phylum            =
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*Small, shallow buccal capsule
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|class              =[[:Category:Nematodes|Nematoda]]
 
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|sub-class          =
 
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|order              =
 
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|super-family      =[[:Category:Strongyloidea|Strongyloidea]]
 
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|family            =Strongylidae
 
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|sub-family        =
 
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|genus              =
 
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|species            =
 
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}}
 
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Also known as: '''''Trichonema spp.
 
  
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==Introduction==
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'''Microscopic''':
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''Cyathostomins'' are a group of '''small strongyles'''. The majority of ''cyathostomins'' are similar in terms of both morphology and behaviour.  There are over 50 different species of small equine ''strongyle'', and they are of huge significance throughout the United Kingdom.  They commonly cause severe acute diarrhoea and colic - [[Cyathostomosis]].
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*Buccal capsule shape
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*Double row of leaf crowns
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*Teeth may be present
  
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==Identification==
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==== Life-cycle ====
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They are small worms, generally less than 1.5cm long.  They also have a distinctive, small buccal capsule.  They also have two rows of leaf crowns, both internal and external.
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*Infection by ingestion of L3
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*Larvae invade mucosa of large intestine
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*Larvae may develop to L4 without interruption
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*Cyathostomin larvae can arrest at EL3 stage
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*L4 emerge into gut lumen and mature to adult worms
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*Prepatent period 8-12 weeks (depending on species)
  
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The species range in colour from white to dark red.
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==== Pathogenicity ====
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'''General''':
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==Hosts==
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*Adult and larval worms are plug feeders, restricting the damage to more superficial mucosa
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Horses and donkeys.
 
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==Life Cycle==
 
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L1-L3 development occurs on the pasture. The rate and extent of development and therefore infective 3rd stage larval challenge is directly affected by environmental conditions. At temperatures below 6 degrees centigrade minimal egg hatching and larval development occur (AAEP parasite control guidelines, 2013).
 
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Infective L3 larvae ingested by the grazing horse penetrate the large intestinal mucosa where they are  quickly (within a few days) encased in a fibrous capsule to become 'encysted'.  At this stage they are known as EL3, and have two potential options. Firstly, they may either become 'hypobiotic', remaining dormant for several months to years.  Hypobiosis usually occurs late autumn/ early winter in temperate climates. Alternatively EL3 may evolve directly into LL3 and then L4. After emergence of the cyst, L4 transform into L5 and then adults in the lumen of the caecum and colon. Importantly, since egg laying adults may not yet be present, a horse may be habouring large numbers of encysted small redworm despite a negative or low faecal worm egg count (FWEC).
 
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Highest egg shedding is in the spring months.  The larvae, which represent 90% of the population, are at maximal levels in the autumn.
 
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Only two anthelminitics have activity against encysted stages of small redworm, a single dose of moxidectin (MOX) or a 5-day course of fenbendazole (5d-FBZ). At 8 weeks post treatment with moxidectin EL3 stages are eliminated (Bairden et. al., 2006). Due to widespread resistance to fenbedazole a faecal egg count reduction test is recommended prior to using it for treatment of the encysted stages (Matthews, 2008). Killing of encysted mucosal larvae due to 5dy-FBZ has been associated with severe tissue damage, which clinically may correspond to reactions caused by synchronous mass emergence of fourth stage larvae (a condition known as larval cyathostominosis).  This effect did not occur after treatment with MOX (Steinbach et. al., 2006)   
 
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{{Learning
 
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|flashcards = [[Horse_Nematode_Flashcards|Horse Nematode Flashcards]]
 
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|literature search = [http://www.cabdirect.org/search.html?q=%28%28title%3A%28Trichonema%29%29%29+OR+%28%28title%3A%28Cyathostomins%29%29%29 Cyathostomins publications]
 
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|Vetstream = [https://www.vetstream.com/canis/search?s=nematode Nematodes]
 
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}}
 
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{{review}}
 
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{{OpenPages}}
 
  
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'''Cyathostominosis''':
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*Initial infection (L3) → local inflammatory response
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*Developing L4s can be seen as brown flecks in the mucosa
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*They can be present in very large numbers (→ the so-called "pepper-pot lesion")
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*Larval emergence throughout '''summer/autumn''' and plug-feeding of adults → major contributor to the "wormy" horse:
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**Unthriftiness
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**Poor coat
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**Anaemia
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**Diarrhoea)
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*May be tens or hundreds of thousands of adults and millions of mucosal larvae present
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*Emergence of massive numbers of previously arrested larvae in '''late winter/early spring''' → massive inflammatory infiltration → serious disease characterised by severe diarrhoea and/or weight loss (larval or Type 2 cyathostominosis)
 
[[Category:Strongyloidea]][[Category:Horse_Nematodes]]
 
[[Category:Strongyloidea]][[Category:Horse_Nematodes]]
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[[Category:Expert_Review]]
 

Revision as of 21:55, 26 April 2010

Small strongyles (Cyathostomins)

Morphology

Gross:

  • Small worms, <1.5cm long
  • Small, shallow buccal capsule

Microscopic:

  • Buccal capsule shape
  • Double row of leaf crowns
  • Teeth may be present

Life-cycle

  • Infection by ingestion of L3
  • Larvae invade mucosa of large intestine
  • Larvae may develop to L4 without interruption
  • Cyathostomin larvae can arrest at EL3 stage
  • L4 emerge into gut lumen and mature to adult worms
  • Prepatent period 8-12 weeks (depending on species)

Pathogenicity

General:

  • Adult and larval worms are plug feeders, restricting the damage to more superficial mucosa

Cyathostominosis:

  • Initial infection (L3) → local inflammatory response
  • Developing L4s can be seen as brown flecks in the mucosa
  • They can be present in very large numbers (→ the so-called "pepper-pot lesion")
  • Larval emergence throughout summer/autumn and plug-feeding of adults → major contributor to the "wormy" horse:
    • Unthriftiness
    • Poor coat
    • Anaemia
    • Diarrhoea)
  • May be tens or hundreds of thousands of adults and millions of mucosal larvae present
  • Emergence of massive numbers of previously arrested larvae in late winter/early spring → massive inflammatory infiltration → serious disease characterised by severe diarrhoea and/or weight loss (larval or Type 2 cyathostominosis)
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