Relation between EP-like lesions and pleurisy with pluck and gut lesions in slaughtered pigs in Northern Portugal

Respiratory diseases have a great impact in the swine production industry. Macroscopic lesions in lungs are often detected during routine post-mortem inspection in the slaughterhouse, with enzootic pneumonia-like lesions (EP-like lesions) and pleuritic lesions being the most common. EP-like lesions, which are primary related with Mycoplasma hyopneumoniae infection, are characterised by consolidation areas, demarcated purple or grey areas in the lungs. Actinobacillus pleuropneumoniae is a respiratory pathogen and the suggestive lesions associated with previous infections of this agent are commonly chronic pleurisy lesions located in the dorso-caudal regions from the lungs. This type of lesion is commonly evaluated by the Slaughterhouse Pleurisy Evaluation System (SPES). The aim of this study was to determine the occurrence of EP-like lesions and pleurisy in 2,142 finishing pigs from 18 different farms (central Portugal, southern Portugal, and northern Spain), the association between EP-like lesions and pleurisies, and the relationship with pluck lesions (lobe scars, emphysema, lung congestion, pericarditis, liver milk spots lesions, and steatosis) and gut lesions (splenitis, pancreatitis, enteritis). For this purpose, EP-like lesions were classified per lobe under the method of enzootic pneumonia–like lesions. Pleurisy lesions were classified under the SPES score method. The presence of other lesions such as pericarditis, liver milk spots, splenitis, pancreatitis, lymphadenitis, and enteritis were also evaluated. Descriptive and multivariate logistic regression analyses were carried out. A variable was considered statistically significant when its P-value≤ 0.05, i.e. its 95% confidence interval of the Odds Ratio (OR) does not contain 1. Among the sample, 41.1% pigs presented EP-like lesions (20.5% registered EP-like lesions scored 1–3, and 20.7% scored 4–24). Around 12% of the sample presented pleurisy, of which 4.8% were of a degree 4 level. Following the EP-like lesions and pleurisy, liver milk spots and pericarditis were the most frequent lesions (4.8% and3.6%, respectively). In this study, the most affected lobes by EP-like lesions were the medial and cranial lobes. The higher the EP-like lesion score, the lower the incidence of presenting an SPES score of 4 (OR=0.38, P<0.001). The higher the SPES scores, the lower the incidence of an EP-like lesion score of category 1 (OR=0.86, P=0.031) or category 2 (OR=0.71, P<0.0001). Pericarditis was associated with a higher incidence of SPES scores 1 (OR=8.57, P<0.001), 2 (OR=7.29, P<0.001), or 4 (OR=26.55, P<0.001). Consolidated pneumonia lesions were the most common cause of partial rejection for human consumption, followed by pleuritic lesions, milk spot lesions, and pericarditis. This study reinforces the importance of monitoring respiratory findings of pig carcasses at the slaughterhouse. It is advantageous to assess the animal’s production performance and welfare. Moreover, lung lesions are closely associated with other findings in tissues and organs with economic value, which can be subclinical or difficult to diagnose in live animals. Furthermore, to the best of our knowledge, this is the only study of its kind carried out in Portugal.