Enzootic Pneumonia in Pigs: Welfare Impact of a Ubiquitous Disease

How enzootic pneumonia and porcine respiratory disease complex affect pig welfare in commercial production and what prevention and management strategies reduce suffering.

Key Facts

Enzootic pneumonia, caused primarily by Mycoplasma hyopneumoniae, is one of the most economically significant and welfare-compromising diseases in pig production globally
The pathogen damages respiratory cilia, predisposing pigs to secondary bacterial infections that cause pneumonia with welfare-significant clinical signs
Prevalence at slaughter in some regions exceeds 80% of pigs showing lung lesions indicative of past or active respiratory disease
Clinical signs include coughing, laboured breathing, reduced growth, and in severe cases respiratory distress and death
Vaccination programmes, combined with all-in all-out management and air quality optimisation, significantly reduce disease burden
Ammonia from pig waste impairs respiratory defence mechanisms and worsens lung disease; ventilation management is a critical welfare lever
Early treatment with appropriate antibiotics reduces duration of suffering; however, reliance on treatment rather than prevention raises AMR concerns

Welfare Considerations

Enzootic pneumonia and associated respiratory complex represent chronic, widespread welfare suffering in commercial pig production. The high prevalence of lung lesions at slaughter demonstrates how normalised respiratory disease has become — lesions that would be considered serious pathology in other contexts are almost universal in some production systems. Active disease causes acute suffering from coughing, dyspnoea, and reduced feed intake. Chronic subclinical disease — pigs with lung damage that are not visibly sick — still compromises respiratory function and quality of life without triggering intervention. The welfare case for prevention over treatment is strong: vaccination, biosecurity, and air quality management address root causes while reducing antibiotic reliance. The correlation between good air quality and welfare is direct — ammonia reduction improves both respiratory health and overall pig welfare.

What You Can Do

Support pig production standards that require robust respiratory disease management plans including vaccination and ventilation requirements
Advocate for ammonia emission standards in pig housing as both a welfare and environmental measure
Choose pork from farms with transparent health records and low antibiotic use — these are proxies for better welfare management
Support research into Mycoplasma vaccine development and non-antibiotic prevention strategies
Engage with farm policy that incentivises proactive disease prevention over reactive antibiotic treatment