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| − | == Gastrointestinal Nematodes == | + | {{frontpage |
| − | ==== Introduction ====
| + | |pagetitle = Horse Nematodes |
| − | [[Image:Parascaris equorum.jpg|thumb|right|150px|''Parascaris equorum'' - Joaquim Castellà Veterinary Parasitology Universitat Autònoma de Barcelona]]
| + | |pagebody = |
| − | [[Image:Parascaris equorum2.jpg|thumb|right|150px|''Parascaris equorum'' - Joaquim Castellà Veterinary Parasitology Universitat Autònoma de Barcelona]]
| + | |contenttitle = Content |
| − | [[Image:Parascaris equorum3.jpg|thumb|right|150px|''Parascaris equorum'' - Joaquim Castellà Veterinary Parasitology Universitat Autònoma de Barcelona]]
| + | |contentbody = |
| − | [[Image:Parascaris equorum4.jpg|thumb|right|150px|''Parascaris equorum'' - Joaquim Castellà Veterinary Parasitology Universitat Autònoma de Barcelona]]
| + | <big><b> |
| − | [[Image:Strongylus.jpg|thumb|right|150px|''Strongylus'' - Joaquim Castellà Veterinary Parasitology Universitat Autònoma de Barcelona]] | + | <br> |
| − | Many nematode species occur in the equine gastrointestinal tract, although not all are of equal importance:
| + | [[Horse Nematode Overview|Overview]] |
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| − | {| style="width:75%; height:200px" border="1"
| + | [[Strongyles]] |
| | + | :[[Large Strongyles]] |
| | + | ::''[[Trichostrongylus axei]] |
| | + | ::''[[Triodontophorus]] |
| | + | :[[Cyathostomins]] |
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| − | !'''Stomach'''
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| − | !'''Small Intestine'''
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| − | !'''Large Intestine'''
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| − | |-
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| − | *''Habronema (Draschia)''
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| − | *''Trichostrongylus axei''
| + | ''[[Dictyocaulus arnfieldi]] |
| − | |
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| − | *''Parascaris''
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| − | *''Strongyloides''
| + | ''[[Habronema and Draschia spp.]] |
| − | |
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| − | *''Strongylus'' species
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| − | *Cyathostomins
| + | ''[[Onchocerca spp.]] |
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| − | *''Triodontophorus'' species
| + | ''[[Oxyuris equi]] |
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| − | *''Oxyuris equi''
| + | ''[[Parafilaria spp.]] |
| − | |-
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| − | |}
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| | | | |
| − | == [[Strongyles]] (Red worms) ==
| + | ''[[Parascaris equorum]] |
| − | The strongyles that occur in the horse can be divided on the basis of size into two groups
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| − | *[[Large Strongyles|'''Large''' strongyles]]
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| − | **''[[Strongylus]]'' species (3 species; used to be widespread prior to the introduction of worm control programmes; now uncommon)
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| − | **''[[Triodontophorus]]'' species (common)
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| − | *'''Small''' strongyles
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| − | **Also known as [[Cyathostomins]] (preferred term), cyathostomes, trichonemes or small redworms
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| − | **Cyathostomins (widespread, including 4 genera and over 40 species of worms)
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| | + | ''[[Setaria spp.]] |
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| | + | ''[[Strongyloides]] |
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| | + | ''[[Thelazia lacrymalis]] |
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| − | === Small strongyles (Cyathostomins) ===
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| − | ==== Morphology ====
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| − | '''Gross''':
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| − | *Small worms, <1.5cm long
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| − | *Small, shallow buccal capsule
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| − | '''Microscopic''':
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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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| | | | |
| − | ==== Life-cycle ====
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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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| | | | |
| − | ==== Pathogenicity ====
| + | [[Horse Nematode Flashcards|Flashcards]] |
| − | '''General''':
| + | <br> |
| − | *Adult and larval worms are plug feeders, restricting the damage to more superficial mucosa
| + | <br> |
| | + | </b></big> |
| | + | |logo=Horse-logo.png}} |
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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)
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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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| − | '''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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| − | '''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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| − | ==== 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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| − | ==== Pathogenesis ====
| + | [[Category:Horse Parasites]] |
| − | 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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| − | | |
| − | ==== 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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| − | '''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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| − | | |
| − | '''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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| − | '''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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| − | '''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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| − | '''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]]
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