3,938 bytes removed ,  21:57, 26 April 2010
no edit summary
Line 22: Line 22:  
*''Parascaris''
 
*''Parascaris''
   −
*''Strongyloides''
+
*''[[Strongyloides]]''
 
|
 
|
*''Strongylus'' species
+
*''[[Strongylus]]'' species
   −
*Cyathostomins
+
*[[Cyathostomins]]
   −
*''Triodontophorus'' species
+
*''[[Triodontophorus]]'' species
    
*''Oxyuris equi''
 
*''Oxyuris equi''
Line 49: Line 49:       −
=== General epidemiology of large and small strongyles ===
  −
'''Strongylosis occurs in'''
  −
*Young horses
  −
*Adult animals (especially if overcrowding, poor hygiene)
  −
*Animals on permanent pasture
     −
'''Sources of infection'''
  −
*Overwintered L3 on pasture
  −
*Many adult horses pass significant numbers of strongyle eggs throughout their lives
  −
*"Spring rise" in faecal egg output occurs in both breeding and non-breeding horses
  −
  −
'''Pattern of infection on pasture'''
  −
*Pattern of L3 on pasture is similar to gastrointestinal worms in cattle
  −
*Main difference is that the mare makes a major contribution to pasture contamination (c.f. cow)
  −
  −
'''Hypobiosis of cyathostomin larvae'''
  −
*Occurs throughout the year, but particularly in '''late summer/autumn'''
  −
*EL3 may remain arrested for years
  −
*Resumption of normal development can occur
  −
**seasonally in '''late winter/early spring'''
  −
**following removal of adult worm population via anthelmintic treatment
  −
  −
==== Larval cyathostominosis ====
  −
*Sudden onset diarrhoea and/or weight-loss
  −
*Diagnosis difficult, prognosis guarded
  −
*Generally in '''late winter/spring'''
  −
*Usually <5 years old
  −
*Sporadic, but increasing in incidence
  −
*Hyperglobulinaemia, especially IgG(T)
  −
*Hypoalbuminaemia
  −
*Leukocytosis
  −
*Sometimes peripheral oedema
  −
*Faecal egg-count low (disease caused by emerging larvae)
  −
*Larvae may be found in faeces or on faecal glove
  −
  −
==== Pathogenesis ====
  −
Resumed development of massive numbers of larvae → subsequent emergence of bright red L4 → massive eosinophilic infiltration of mucosa → catarrhal and haemorrhagic colitis
  −
  −
==== Control of cyathostomin infections in horses ====
  −
'''Anthelmintics'''
  −
*Only 3 chemical groups currently available
  −
**Avermectin/milbemycins
  −
**Benzimidazoles
  −
**Pyrantel
  −
*Resistance is an emerging problem (especially to benzimidazoles)
  −
  −
'''Target life-cycle stages'''
  −
*These are not all equally susceptible to each anthelmintic
  −
*Pyrantel is affective against
  −
**Adult worms in the lumen
  −
*Ivermectin or a one off administration of Fenbendazole is affective against
  −
**Adult worms and L4 in the lumen
  −
*Moxidectin or a 5 day course of Fenbendazole is affective against
  −
**Adult worms and L4 in the lumen
  −
**Developing and hypobiotic L3 in the mucosa
  −
  −
'''Egg reappearance period'''
  −
*This is the time from treatment until eggs reappear in the faeces. It is determined by
  −
**degree of activity against mucosal larval stages
  −
**persistency of anthelmintic treatment
  −
  −
'''Prevention of pasture contamination'''
  −
*The objective is to create safe grazing by preventing depostion of strongyle eggs onto pasture
  −
*Treat all grazing horses at intervals determined by
  −
**Egg reappearance time of chosen anthelmintic
  −
**Risk level
  −
*Treat all new arrivals and stable for 48-72 hours so that eggs are not passed onto pasture
  −
*Adopt strategy that will minimise risk of resistance developing (you may need to include tapeworm and stomach bots in your scheme)
  −
*No new eggs passed → no new L3 developing, however it is important to use epidemiological knowledge to predict how long existing L3 will survive as the pasture will not be safe for use before then
  −
*Remove faeces from paddocks at least weekly:
  −
**This markedly reduces dependence on anthelmintics
  −
**Increases available grazing
  −
**But is labour intensive and less effective in rainy weather
  −
*Examine faecal samples twice yearly to monitor effectiveness of your chosen strategy
  −
  −
'''Pasture management'''
  −
*Reserve clean grazing for nursing mares and foals
  −
*Rest pastures used the previous year until overwintered L3 have gone
  −
*Mixed or alternate grazing with cattle or sheep
  −
**These are refractory to most horse worms, except ''T.axei''
  −
  −
'''Chemoprophylaxis of larval cyathostominosis'''
  −
*Needed if a horse is known to have grazed heavily contaminated pasture and may therefore be harbouring massive numbers of hypobiotic larvae
  −
*Fenbendazole treatment given daily for 5 consecutive days in autumn or winter will reduce the risk of clinical disease developing.
      
[[Category:Nematodes]][[Category:Horse]]
 
[[Category:Nematodes]][[Category:Horse]]
Author, Donkey, Bureaucrats, Administrators
53,803

edits