Revision SI parasite ruminants Flashcards
Discuss nematodirus?
- Is a trichostrongyle nematode
- Common in temperate zones
- It is of special significance to lambs in UK
- Scottish border and northern England
- Inhabits small intestine of ruminants
Which species of nematodirus effect which type of ruminant?
Common Species
- N. battus* Sheep and Calves (occasionally)
- N. fillicolis* Sheep
- N. spathiger* Sheep
- N. helvetianus* Cattle
What is the nematodirus life cycle?
Discuss the uniqueness of N. battus?
- Preparasitc phase (L1-L3) occurs within egg shells
- Eggs extremely tough and resistant to freezing and drought, viable up to 2 years on pasture
- Hatch is stimulated by cold period followed by a mean day/night temperature of ~ 10 0 C, but L3 are susceptible to climate and need to be ingested quickly. Thus, this is usually the first species to peak on pasture in spring
- Large number simultaneously burrowing into the gut cause the pathology (larvae not adult)
- Is N. battus hatching only occur from eggs excreted in previous year?
- No, some eggs deposited in spring can hatch in autumn of the same year causing contamination of pasture at this time
Clinical signs of nematodirus infection?
Clinical signs
- Acute onset in young recently waned lambs ( 6 weeks-4 months )
- Rapid weight loss, Watery diarrhoea/dehydration
- Sudden death; disease usually first reported in May/June
- Very often a vet will be called because of sudden death (onset and disease progression can be very fast)
- The principal pathogenic damage is due to the developing larval stages ( damage of villi and erosions of mucosa )
How can weather be used to know when to treat N. battus?
- Ministry of Agriculture Britain developed forecasting system based on soil temp in spring, which can predict the likely severity of Nematodirus infection
- Three treatments during May-June in years with predicted severe diseases, and two in other years
- Ewes dosed prior to lambing
Rotational grazing:
- >2 year rotation is needed on previously infected pasture
- Rotation: Sheep (Y1), cattle (Y2), conservation (Y3) if possible
Discuss nematodirus immunity?
- Strong age-related immunity (immunity occurs after about 3 months of age )
- Increased eosinophils and mast cells at site of infection
- Nematode specific sIgA and serum IgG Villus shedding (important rejection mechanism when infected with species which are closely associated with villi)
Discuss trichostrongylus?
- Small, hair like worms
- Up to 0.7 mm long (difficult to see by naked eye )
- Bursated nematode
- Inhabits alimentary tract of animals and birds
- Small buccal capsule
- Direct, non-migratory life cycle
- Infection via ingestion of free L3
Which species of trichostrongylus infects which ruminants?
- Common species:
- T. colubriformis (sheep, goats and cattle)
- T. capricola
- T. vitrinus
- Trichostrongylus axei (Sheep, goats and Cattle) live in abomasum
- T. tenuis (birds)
Outline the trichostrongylus lifecycle?
Look at this image of trichostrongylus pathology?
Clinical features of trichonstrongylus infection?
- Acute diarrhoea in young
- Chronic diarrhoea in older animals
- Intestine is inflamed with hyperplasia and there may be blood spots
- Mesenteric lymph nodes are enlarged
- May cause bottle jaw
- PGE (Parasitic Gastro-Enteritis) due to trichostrongylosis has been seen in UK winter since warmer wetter winters have favoured increased L3 survival
Discuss immune exclusion in trichostrongylus infection?
Immune exclusion – exclusion of/barrier against L3 Mucus from immune sheep prevented establishment of T. colubriformis (and other nematodes) in naïve sheep intestine. sIgAand a mucus IgG recognises 3 different classes of L3 cuticular Ags
Discuss self cure immunity in trichostrongylus infection?
Self cure – expulsion of adults in intestine
This involves mast cells, IgE and eosinophils ( Th2 induced hypersensitivity response )
Romnet sheep (selected for resistance to T. colubriformis ) have increased expression of IL-5 and IL-13 in mesenteric lymphoid cells
- IL-5 (activates eosinophils)
- IL-13 stimulates eotaxin ( chemokines ) and eosinophil migration and class switching to IgE
Self cure is T-cell induced and can be prevented in T-cell ablation models or can be induced when naïve animals have T-cells from immune animals adoptively transferred into them
Discuss Trichostrongylus tenius?
Nematode infects
- chicken
- guinea fowl
- pheasant
- quail
Most notable impact has been on red grouse populations in North east and West England and Scotland Grouse shooting industry worth an estimated 15-20 million pa in Scotland
What is the lifecycle of Trichostrongylus tenius?
