Lungworm in Cattle: Welfare Implications & Control

Lungworm and Bovine Welfare

Bovine lungworm disease (husk/hoose), caused by Dictyocaulus viviparus, is a parasitic bronchitis that causes severe respiratory disease in cattle, particularly in first-season grazing animals. Outbreaks can be dramatic, with sudden onset of severe respiratory distress across a group.

Disease Progression and Welfare Impact

Stage 1 — Prepatent (invasion): Larvae migrate through intestinal wall and lungs; mild respiratory signs begin.
Stage 2 — Patent (consolidation): Adult worms in airways cause severe pneumonia, coughing, laboured breathing, and fever. Significant suffering.
Stage 3 — Post-patent (resolving): After worm death, hypersensitivity reactions and secondary bacterial pneumonia can still cause significant morbidity.
Stage 4 — Re-infection syndrome: In sensitised adult cattle, sudden massive larval challenge causes acute, severe respiratory distress — a welfare emergency.

Risk Factors

First-season grazing animals lacking immunity
Wet summers favouring larval survival on pasture
Adult cattle losing immunity after several years housed indoors
Introduction of larvae via carrier animals

Diagnosis

Clinical signs: coughing, tachypnoea, dyspnoea in groups of cattle
Baermann technique on fresh faeces to detect larvae
Post-mortem examination for severe outbreaks
Differential diagnosis from bovine respiratory disease complex

Control Strategies

Strategic anthelmintic treatment: Levamisole, benzimidazoles, or macrocyclic lactones at housing; timing depends on farm history and risk.
Live vaccine (Huskvac): Oral vaccination of calves before turnout provides protection; reduces reliance on anthelmintics.
Pasture management: Avoiding pastures with known contamination history in vulnerable groups.
Monitoring: Cough scoring systems allow early detection of outbreaks before severe disease develops.
Treatment of outbreaks: Prompt anthelmintic treatment of the group, with supportive care for most severely affected animals.

Key Takeaways

Lungworm causes acute, severe respiratory suffering in cattle. Effective control using strategic anthelmintic treatment or vaccination, combined with vigilant monitoring, is essential to prevent welfare emergencies during the grazing season.