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29 Cards in this Set
- Front
- Back
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Genera of Trichostrongyles in the small intestine of ruminants |
Trichonstrongylus Cooperia Nematodirus |
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Common name and main host for members of Trichostrongylus genus |
Black scour worm
Sheep |
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Species of Trichostrongylus genus |
T. colubriformis
T. vitrinus T. rugatus T. axei |
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Which species if Trichostrongylus genus is not found in the small intestine? |
T. axei (found in stomach and abomasum) |
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Main hosts and location of Trichostrongylus |
Sheep, goats Duodenum |
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How do we differentiate between species of Trichostrongylus? |
Size and shape of spicules |
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Barb-like tip T. colubriformis |
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Tapering end T. vitrinus |
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Thick and dissimilar T. rugatus |
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Dissimilar and unequal T. axei |
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Distribution of Trichostrongylus |
Higher rainfall areas Main sheep raising areas Species differ in regions |
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Which Trichostrongylus species occurs in summer rainfall areas? |
T. colubriformis |
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Which Trichostrongylus species occurs in cooler, moist areas? |
T. vitrinus |
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Which Trichostrongylus species occurs in dry areas? |
T. rugatus |
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Life cycle of Trichostrongylus |
Eggs laid in faeces L1 hatches L1 & L2 develop in faeces L3 retains cuticle of L2 as sheath L3 migrates out of faeces and up onto grass L3 ingested by sheep Exsheaths in rumen Develops in small intestine |
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Prepatent period of Trichostrongylus |
21 Days |
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Development of Trichostrongylus in the small intestine |
Development occurs in duodenum Moult to L4 occurs after 5 days Moult to adult occurs at 10 days Nematodes are intraepithelial parasites |
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What do Trichostrongylus do to sheep? |
Villus atrophy
Protein loss Reduced absorption of Ca and PO4 Anorexia Diarrhoea |
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Villus atrophy |
Mucosal glands enlarged Inflammatory cells in lamina propria Increased rate of cell exfoliation Abnormal epithelial cell breaks in epithelium |
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Hypoproteinaemia |
Breaks in epithelium and increased permeability of capillaries Leakage of plasma proteins into gut Hypoproteinaemia/hypoalbuminaemia associated with up to 20% reduction in wool production and reduced growth rate Globulin concentration in blood rises as host mounts immune response |
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Ca and PO4 absorption |
Absorption occurs in duodenum Malabsorption of Ca and PO4 occurs as posterior half of SI cannot compensate Blood Ca conc has to be maintained within narrow range Hypophosphataemia is seen Reduced bone growth (reduced osteoblastic activity) |
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Anorexia |
Feed intake reduced Mechanism not known Major effect on growth rate |
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Diarrhoea |
Parasites secrete analogues of parasympathetic transmitters Increase frequencey and strength of peristaltic waves Together with poor absorption leads to diarrhoea |
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Host response to infection with Trichostrongylus |
Immune response only if > 5 months of age Threshold of 3000 worms Expulsion of worms rarely 100% Immunity against incoming larvae, mainly cellular Eosinophils can kill larvae Scouring can occur in immune sheep 1. Goblet cell hyperplasia increase mucus 2. Mucus entangles worms 3. Mucus of immune sheep paralyses worms 4. Eosinophils, mast cells in lamina propria discharge histamine, serotonin and cyokines 5. Expulsion of nematodes |
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Is there a vaccine for Trichostrongylus |
No |
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Seasonal patterns of Trichostrongylus: |
Summer too hot and dry
Autumn moist: larvae develop Winter moist grass short: large #s ingested Spring: larvae diluted due to rising temperatures and long pasture |
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Seasonal patterns of Trichostrongylus: Summer rainfall zones |
Winter too cold or dry Larvae develop in spring Maximum numbers in summer |
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Seasonal patterns of Trichostrongylus: Temerate (northern hemisphere) |
Winters too cold Develop during spring Maximum in autumn |
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Mortalities due to Trichostrongylus |
>60.000 nematodes can kill young sheep In winter rainfall zone deaths seen mid winter Seasonal occurence |
