Ruminant Lungworm Flashcards
What is the bovine lungworm? What condition does it cause?
- Dictyocaulus viviparous
- trichostrongyle of trachea and large bronchi
> parasitic bronchitis (husk, hoose)
What effect does parasitic bronchitis have on cattle?
Calves: poor weight gain
Dairy: lowered milk yield
Which age cows are affected by parasitic bronchitis?
- used to be younger cows
- now more comonly older
Which species other than cattle does dictyocaulus affect?
farmed deer
Outline lifecycle of dictyocaulus viviparous?
> Penetration phase (week 1)
- larvae ingested from pasture, mature and migrate from intestines to lungs [no clinical signs]
Prepatent phase (weeks 1-3)
-development and migration of larvae -> bronchiolitis and eosinophilic exudate, blocks air passages -> alveolar collapse [tachynpniea, coughing]
Patent phase (weeks 4-8)
- worms mature, lay eggs [bronchitis due to adult worms, parasitic pneumonia -> areas of consolidation due to reaspiration of eggs and larvae -> cellular infiltration by polymorphs, macrophages, and FB giant cells]
Post-patent phase (weeks 8-12)
- most worms expelled [clinical signs flare up in 25% cases] caused by alveolar epithelialisation, interstitial emphysema, pulm oedema, 2* bacterial inflam)
Is immunity to dictyocaulus possible? Are older cattle more susceptible than younger?
YES! Rapidly acquired following heavy exposure
- Older cows not necessarily immune unless previously exposed ie. age persay not protective
Pathogenesis of re-infection DV
- immune cattle only show clinical signs if exposed to massive challenge
- larvae reaching lungs killed by immune response
- > parasitic granuloma (5mm, grey green)
- > eosinophilic plugs in bronchioles
Diagnosis of dictyocaulus viviparous based on..?
> seasonal incidence
previous grazing history
clinical signs
feacal exam using Baerman technique (funnel, filter, poo floaty)
- examin healthy AND sick calves/cattle (often no L in cows)
- all + samples potentially significant
- carrier animals (30% yearlings, 5% cows, vaccinated cattle)
blood and milk for adults (variable results depending on Ag used, herd better than individual)
PM - plum coloured consolidation lesions on diaphragmatic lobes, worm recovery lung perfusion technique [tie off PVs, flush through PAs, collect washings from trachea over sieve )
grass exam for larvae
response to anthelmintics
How may lungworm larvae be identified from GIT larvae?
> lungworm - short 300m - blunt tail - intestinal granules (clear) > GIT - longer 700-1000m - longer, thinner tail - intestinal cells (dark)
How may bovine lungworm be controlled?
Bovilis “Huskvac”
- 1st season claves, >2 months old, reared indoors
- Oral vax (1000x irradiated DV L3 per dose)
- Vaccinate 6 and 2 weeks pre turnout
- NEVER mix vax and non vax calves
How long does vaccine immunity last for? (DV)
- life long protection following 2 doses
- immunity reinforced by field challenge
- prevent DISEASE not infection
- breakdown can occour due to overwhelming challenge, improper storage/administration and concurrent disease
What anthelmintic control strategies are advocated for dictyocaulus viviparous?
- modern anthelmintic with long residual activity
- eg. doramectin
- at 0 and 8 weeks post turnout ( 5 week residual activity v lungworm)
When may clinical disease occour despite anthelmintic strategies? DV
- with long grazing seasons
Which is the most important lungworm affecting sheep?
- dictyocaulus filaria
sheep and goats
CLinical signs of ovine lungworm?
- chronic cough and unthriftiness
- temperate areas - sporadic
- warmer climates - disease outbreaks
