Pig Welfare: Respiratory Disease
Porcine Respiratory Disease Complex (PRDC) is among the most significant welfare and economic challenges in pig production globally. Multiple pathogens interact with environmental and management factors to cause disease ranging from subclinical growth depression to fatal pneumonia.
Key Respiratory Pathogens
PRRS virus (Porcine Reproductive and Respiratory Syndrome): One of the most economically damaging pig diseases, PRRS causes reproductive failure in sows and respiratory disease in growers. Affected pigs show laboured breathing, fever, poor growth, and increased susceptibility to secondary infections. PRRS immunosuppression is a major driver of PRDC complexity.
Swine Influenza Virus (SIV): Highly contagious, causing acute fever, respiratory signs, and rapid spread through herds. While mortality is usually low, morbidity (animals feeling acutely unwell) is high and productivity losses significant. Zoonotic potential adds public health relevance.
Actinobacillus pleuropneumoniae (App): Causes severe, often fatal pleuropneumonia with rapid onset. Acute cases show extreme distress — laboured breathing, bloody oral and nasal discharge, and high fever. Chronic survivors show reduced growth and welfare compromise from lung adhesions and consolidation.
Mycoplasma hyopneumoniae: The primary driver of Enzootic Pneumonia, causing chronic coughing and poor growth. More commonly associated with chronic welfare compromise than acute mortality.
Environmental Risk Factors
Respiratory disease is strongly influenced by building environment. Inadequate ventilation (high ammonia, moisture, or dust) damages respiratory mucosa, impairing pathogen clearance. Chilling, particularly in the nursery phase, suppresses immune function. High stocking densities increase pathogen load and transmission.
All-in/all-out management (complete emptying, cleaning, and disinfecting between batches) dramatically reduces pathogen buildup compared to continuous flow systems and is a cornerstone of respiratory disease prevention.
Welfare Assessment and Monitoring
Slaughterhouse lung scoring provides population-level monitoring — the prevalence and severity of lung lesions indicates respiratory disease history. On-farm, cough monitoring (observation, or automated acoustic monitoring systems) provides real-time surveillance. Clinical health checks noting respiratory rate, nasal discharge, and laboured breathing support early intervention.
Treatment and Prevention
Vaccination programmes for PRRS, SIV, App, and Mycoplasma form the backbone of disease prevention alongside biosecurity. Antimicrobial treatment of acutely affected pigs reduces suffering and mortality, but antimicrobial stewardship principles require selecting appropriate agents under veterinary guidance and minimising preventive use.
Improving building design and management — particularly ventilation optimisation — often has greater long-term impact on respiratory disease than vaccination or treatment alone.