Occurrence, Severity and Temporal Trends of Enzootic Pneumonia-like Lung Lesions in Hungarian Slaughter Pigs, 2018–2022: Insights from Zero-Inflated Mixed-Effects Models

Porcine respiratory disease complex remains a challenge for pig production, and slaughterhouse lung inspection provides a tool for respiratory health monitoring. This study investigated the occurrence, severity, temporal trends, and anatomical distribution of enzootic pneumonia-like lung lesions in Hungarian slaughter pigs between 2018 and 2022 and evaluated associations with farm size. Of the 13,535 lungs examined, 13,499 with complete lobe-level data were analysed using the Madec scoring system, based on 174 slaughterhouse examinations across 38 farms. Zero-inflated mixed-effects models with a negative binomial distribution were used to analyse lesion occurrence and lesion scores. EP-like lesions (Madec score ≥ 1) occurred in 25.3% of lungs, declining from 57.4% in 2018 to 8.6% in 2022, and mean Madec scores decreased from 2.7 to 0.3. Most lungs (91.0%) scored between 0 and 4, whereas 9.0% had moderate-to-severe lesions (scores 5–28). Lesions were most frequent and severe in the cardiac and apical lobes and showed greater involvement of the right-sided lobes. Farm size was not significantly associated with either model component, although structural zero probabilities were lowest for small and highest for large farms. Structural-zero probability increased over time, indicating that declining overall Madec scores mainly reflected structural zeros rather than conditional-score changes.