Ruminant lungworms Flashcards
What causes bovine lungworm?
Dictyocaulus viviparus
Where is Dictyocaulus viviparus found?
found in the trachea and larger bronchi –> parasitic bronchitis (husk, hoose)
Other than cattle, what species can Dictyocaulus viviparus affect?
farmed deer
Outline immunity to bovine lungworm?
- rapidly acquired
- minimal age resistance
What are the different stages of D. viviparus infection? 4
- Penetration phase (week 1)
- Prepatent phase (weeks 1-3)
- ) Patent phase (weeks 4-8)
- ) Post-patent phase (weeks 8-12)
What happens in the penetration phase (bovine lungworm)?
Week 1 - larvae migrate to lungs, no CS
What happens in the pre-patent phase (bovine lungworm)?
Weeks 1-3
Development + migration of larvae –> bronchiolitis –> eosinphilic exudate –> blocks passage of air –> alveolar collapse distal to blockage –> CS (tachypnoea, dyspnoea)
What happens in the patent phase (bovine lungworm)?
Weeks 4-8
Worms mature and become egg-producing –> bronchitis (adult worms) and parasitic pneumonia (reaspiration of eggs as larvae –> cellular infiltration by polymorphs, macrophages, FB giant cells)
What happens in the post-patent phase (bovine lungworm)?
Weeks 8-12
Period at end of disease when most worms expelled, but CS flare up in 25% cases due to alveolar epithelialisation (alveolar cells replaced by cuboidal cells), interstitial emphysema, pulmonary oedema and secondary bacterial infection
When can cows become reinfected with bovine lungworm?
Immune cows only show CS if exposed to massive challenge. Larvae reach lungs but killed by IR. Pathology: parasite granuloma (5mm, grey-green) and eosinophilic plugs in bronchioles)
How can a diagnosis of bovine lungworms be made in calves?
- seasonal (mid-late summer)
- grazing hx
- CS
- Faecal exam (Baerman) –> larval ID
Features of lungworm larva? 3
- short (300 micrometers)
- blunt tail
- intestinal GRANULES
Features of GIT larvae
- Longer than lungworm larve (700-1000micrometers)
- longer tails
- intestinal CELLS
Which larvae can be present in bovine faeces?
Lungworm only. GIT worms shed eggs so only if faecal sample is left unrefrigerated does it have larvae which hatch out of eggs.
how should you do a faecal exam for bovine lungworm?
examine healthy and sick animals - all positive samples are potentially significant - carrier animals possible (30% yearlings and 5% cows, also vaccinated cows)
Outline PME findings for bovine lungworm
- lesions on diaphragmatic lobes
- Plum coloured areas of consolidation
- Lung perfusion technique to retrieve worms
How can you make a diagnosis of bovine lungworm in adult cattle? 7
- season
- grazing hx
- CS
- Faecal exam - Baerman - as for calves
- Blood and milk ELISA (variable results depending on Ag used, herd results better than individual results)
- grass examination (larvae around dungpats)
- response to anthelmintics
Outline bovine lungowmr vaccination
Bovilis HUSKVAC
- 1st season calves > 2months old, reared indoors
- Oral vaccine (irradiated L3)
- 6 and 2 weeks pre-turnout
- never mix vaccinated and unvaccinated animals (may increase pasture L3 levels to the point that vaccinated animals’ immunity is overcome)
What is an anamestic response?
it is a second response to a vaccine (e.g. Bovilis HUSKVAC) where there is an exaggerated Ab response (especially compared to the 1st vaccine where there is a reasonable Ab response)
Outline the result of Huskvac vaccination - 3
- lifelong protection following 2 doses (immunity reinforced by field challenge)
- prevents disease not infection
- breakdown (overwhelming challenge, improper storage, admin or concurrent disease)
Outline anthelmintic control of bovine lungworm
- long residual activity anthelmintics - e.g. doramectin at 0 and 8 weeks post-turnout (5 weeks residual activity against lungworm) but clinical disease may occur if long grazing season.
Name 3 ovine lungworm species
- Dictyocaulus filaria*
- Muellerius and Protostrongylus
Outline Dictyocaulus filaria LC
- Direct (like D.viviparus)
- PPP 5 weeks (longer than D.viviparus)
Outlien Muellerius and Protostrongylus LC
- Indirect (mollusc IH)
- Adult worms live in alveoli/parenchyma (Muellerius) or small bronchioles (Protostrongylus)
- PPP 6-10 weeks (Muellerius) or 5-6 weeks (Protostrongylus)
Outline pathogenesis of the ovine lungworm species
- DICTYOCAULUS FILARIA - similar to D. viviparus, lesions less widespread as fewer worms
- MUELLERIUS - nodular lesions contain adult worms, eggs and larvae in lung parenchyma
- PROTOSTRONGYLUS - adult wroms block small bronchioles –> debris accumulates distal to blockage
Diagnosis - ovine lungworms - 4
- Season
- grazing hx
- faecal exam (Baerman) - healthy and sick lambs/kids, ID larvae to genus level to differentiate whether Dictyocaulus or not as this is the most pathogenic of the 3 ovine lungworms and to aid prognosis.
- PME
What is the main difference between the larvae of Dictyocaulus filaria and Muellerius spp?
- DICTYOCAULUS - protoplasmic knob on head
- MUELLERIUS - blunt tail with spine
What is the PME like for D. filaria?
Similar to D.viviparus in cows - lesions mainly in the diaphragmatic lobes and there are plum-coloured areas of consolidation
What is the PME like for Muellerius?
Palpable nodles (‘lead shot’) on/just below the lung surface (adults worms, eggs and larvae)
What is the PME like for Protostrongylus?
Adult worms –> block small bronchioles –> debris accumulates distal to the blockage and forms a conical/triangular area of consolidation in the lung
Outline control strategies for D.filaria
- difficult, outbreaks unpredictable
- PGE control measures normally prevent disease
- OUTBREAK - treat affected, house/move to clean grazing
- Vaccine - no longer available in UK
Outline control strategies for Muellerius and Protostrongylus
- Unlikely to be necessary as NON-PATHOGENIC
- Difficult since wide range of IHs, prolonged survival of larvae in faeces.
