| Line 22: |
Line 22: |
| | *''Parascaris'' | | *''Parascaris'' |
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| − | *''Strongyloides'' | + | *''[[Strongyloides]]'' |
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| − | *''Strongylus'' species | + | *''[[Strongylus]]'' species |
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| − | *Cyathostomins | + | *[[Cyathostomins]] |
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| − | *''Triodontophorus'' species | + | *''[[Triodontophorus]]'' species |
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| | *''Oxyuris equi'' | | *''Oxyuris equi'' |
| Line 49: |
Line 49: |
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| − | === General epidemiology of large and small strongyles ===
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| − | '''Strongylosis occurs in'''
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| − | *Young horses
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| − | *Adult animals (especially if overcrowding, poor hygiene)
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| − | *Animals on permanent pasture
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| | | | |
| − | '''Sources of infection'''
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| − | *Overwintered L3 on pasture
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| − | *Many adult horses pass significant numbers of strongyle eggs throughout their lives
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| − | *"Spring rise" in faecal egg output occurs in both breeding and non-breeding horses
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| − |
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| − | '''Pattern of infection on pasture'''
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| − | *Pattern of L3 on pasture is similar to gastrointestinal worms in cattle
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| − | *Main difference is that the mare makes a major contribution to pasture contamination (c.f. cow)
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| − |
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| − | '''Hypobiosis of cyathostomin larvae'''
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| − | *Occurs throughout the year, but particularly in '''late summer/autumn'''
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| − | *EL3 may remain arrested for years
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| − | *Resumption of normal development can occur
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| − | **seasonally in '''late winter/early spring'''
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| − | **following removal of adult worm population via anthelmintic treatment
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| − |
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| − | ==== Larval cyathostominosis ====
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| − | *Sudden onset diarrhoea and/or weight-loss
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| − | *Diagnosis difficult, prognosis guarded
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| − | *Generally in '''late winter/spring'''
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| − | *Usually <5 years old
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| − | *Sporadic, but increasing in incidence
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| − | *Hyperglobulinaemia, especially IgG(T)
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| − | *Hypoalbuminaemia
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| − | *Leukocytosis
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| − | *Sometimes peripheral oedema
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| − | *Faecal egg-count low (disease caused by emerging larvae)
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| − | *Larvae may be found in faeces or on faecal glove
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| − |
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| − | ==== Pathogenesis ====
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| − | Resumed development of massive numbers of larvae → subsequent emergence of bright red L4 → massive eosinophilic infiltration of mucosa → catarrhal and haemorrhagic colitis
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| − |
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| − | ==== Control of cyathostomin infections in horses ====
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| − | '''Anthelmintics'''
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| − | *Only 3 chemical groups currently available
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| − | **Avermectin/milbemycins
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| − | **Benzimidazoles
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| − | **Pyrantel
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| − | *Resistance is an emerging problem (especially to benzimidazoles)
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| − |
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| − | '''Target life-cycle stages'''
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| − | *These are not all equally susceptible to each anthelmintic
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| − | *Pyrantel is affective against
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| − | **Adult worms in the lumen
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| − | *Ivermectin or a one off administration of Fenbendazole is affective against
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| − | **Adult worms and L4 in the lumen
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| − | *Moxidectin or a 5 day course of Fenbendazole is affective against
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| − | **Adult worms and L4 in the lumen
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| − | **Developing and hypobiotic L3 in the mucosa
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| − |
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| − | '''Egg reappearance period'''
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| − | *This is the time from treatment until eggs reappear in the faeces. It is determined by
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| − | **degree of activity against mucosal larval stages
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| − | **persistency of anthelmintic treatment
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| − |
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| − | '''Prevention of pasture contamination'''
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| − | *The objective is to create safe grazing by preventing depostion of strongyle eggs onto pasture
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| − | *Treat all grazing horses at intervals determined by
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| − | **Egg reappearance time of chosen anthelmintic
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| − | **Risk level
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| − | *Treat all new arrivals and stable for 48-72 hours so that eggs are not passed onto pasture
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| − | *Adopt strategy that will minimise risk of resistance developing (you may need to include tapeworm and stomach bots in your scheme)
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| − | *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
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| − | *Remove faeces from paddocks at least weekly:
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| − | **This markedly reduces dependence on anthelmintics
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| − | **Increases available grazing
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| − | **But is labour intensive and less effective in rainy weather
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| − | *Examine faecal samples twice yearly to monitor effectiveness of your chosen strategy
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| − |
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| − | '''Pasture management'''
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| − | *Reserve clean grazing for nursing mares and foals
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| − | *Rest pastures used the previous year until overwintered L3 have gone
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| − | *Mixed or alternate grazing with cattle or sheep
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| − | **These are refractory to most horse worms, except ''T.axei''
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| − |
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| − | '''Chemoprophylaxis of larval cyathostominosis'''
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| − | *Needed if a horse is known to have grazed heavily contaminated pasture and may therefore be harbouring massive numbers of hypobiotic larvae
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| − | *Fenbendazole treatment given daily for 5 consecutive days in autumn or winter will reduce the risk of clinical disease developing.
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| | [[Category:Nematodes]][[Category:Horse]] | | [[Category:Nematodes]][[Category:Horse]] |