Sheep Respiratory Disease: Welfare and Prevention
Respiratory disease is a leading cause of welfare compromise and mortality in sheep, particularly in housed flocks and young lambs. This page reviews major respiratory conditions, welfare impacts, and best-practice prevention.
Significance of Respiratory Disease in Sheep
Respiratory disease (collectively termed 'ovine respiratory disease complex', ORDC) is consistently ranked among the top welfare and economic problems in UK sheep production. It is the leading cause of antibiotic use in sheep flocks, reflecting both prevalence and the serious welfare and mortality consequences of untreated disease. ORDC affects lambs particularly severely in the first weeks of life and in the post-weaning period, but adult sheep are also vulnerable—especially in housed conditions with poor ventilation.
Causal Agents
ORDC involves multiple pathogens acting synergistically: Mannheimia haemolytica and Pasteurella multocida (primary bacterial pathogens); Mycoplasma ovipneumoniae (a predisposing pathogen affecting mucociliary clearance); Respiratory Syncytial Virus; Parainfluenza Virus 3; and Border Disease Virus. Stress (transport, weaning, housing, nutritional stress) impairs immunity, enabling pathogens normally present in the upper respiratory tract to invade the lungs. Concurrent disease (internal parasitism, trace element deficiency) increases susceptibility.
Clinical Signs and Welfare Assessment
Respiratory disease signs range from subtle to severe: early nasal discharge, dullness, reduced appetite, and slight cough represent moderate welfare compromise detectable by regular pen observation; laboured breathing, open-mouth breathing, extended head-neck posture, and recumbency indicate severe disease requiring immediate intervention. Respiratory scoring systems (Wisconsin respiratory scoring adapted for sheep) enable standardised welfare assessment. Daily pen observations by trained staff identifying early clinical signs enable earlier treatment with better welfare and survival outcomes.
Housing and Ventilation
Poor ventilation is the primary risk factor for ORDC in housed flocks. High humidity, ammonia accumulation, and pathogen aerosols in inadequately ventilated buildings damage mucociliary defences and facilitate infection. Welfare-positive housing design: open ridge ventilation maintaining air movement without direct draughts; two-site housing separating lambs from ewes where feasible; stocking density appropriate for building design; and regular monitoring of air quality (no ammonia smell at animal level, no condensation on surfaces).
Vaccination Programmes
Pasteurella vaccination (Ovipasteurella combined vaccines) provides protection against M. haemolytica and P. multocida when incorporated into appropriate programmes: ewes vaccinated 3-6 weeks pre-lambing confer passive immunity through colostrum; direct lamb vaccination from 4 weeks provides active immunity. Clostridial vaccines (multivalent) should be combined with Pasteurella vaccination where both are used. RSV and PI3 vaccines are available in some markets. Welfare-positive farms develop written vaccination programmes with veterinary advisors specifying timing, products, and records.
Antibiotic Treatment and Stewardship
Antibiotics are essential welfare interventions for bacterial respiratory disease—delaying treatment worsens welfare and reduces survival. Prompt identification and targeted antibiotic treatment, ideally based on sensitivity testing from diagnostic submissions, produces better welfare outcomes than delayed empirical treatment. Antibiotic stewardship principles: use antibiotics only where indicated; use the narrowest appropriate spectrum product; maintain treatment records; and monitor treatment response. UK sheep industry antibiotic use reduction targets require farms to demonstrate responsible use while maintaining welfare-appropriate treatment of sick animals.
Trace Elements and Immunity
Selenium, copper, and cobalt deficiencies impair immune function and increase respiratory disease susceptibility. Selenium deficiency is widespread in UK soils; affected flocks show increased disease prevalence and mortality. Targeted supplementation (based on blood sampling) improves immune competence. Blanket supplementation without testing risks toxicity. Veterinary-guided trace element monitoring and targeted supplementation is welfare-positive—addressing a correctable predisposing factor for respiratory disease.
Summary
Sheep respiratory disease welfare requires integrated prevention: adequate ventilation, appropriate vaccination programmes, targeted supplementation of immunomodulatory trace elements, and early clinical detection enabling prompt treatment. The combination of multiple synergistic pathogens, housing stress, and nutritional factors means no single intervention eliminates ORDC—welfare improvement requires addressing the full complex of risk factors through farm health planning and veterinary partnership.