Actinobacillus pleuropneumoniae post mortem examination

Patho-anatomical lesions are routinely recorded at meat inspection of swine carcasses in Denmark. The original purpose was to safeguard food. For an additional fee, a more thorough post mortem examination of lungs can be performed at the Danish Pig Research Centre (DPRC) with the specific purpose of diagnosing respiratory disorders. However, for the herd manager or veterinarian, it is tempting to use the frequent and free-of-charge recordings from the meat inspection as a proxy for post mortem examination. A previous study found weak to moderate correlations for pericarditis (R²=0.16) and pleuritis (R²=0.67), when slaughterhouse recordings were compared to post mortem examinations.

The purpose of this study was to evaluate if meat inspection recordings of Actinobacillus pleuropneumoniae (App)-like lesions are suitable for monitoring late outbreaks in chronically infected herds. Specifically, the objective was to estimate the correlation between the prevalence of pleuropneumonia found at post mortem examination and the prevalence of App-like lung lesions found at meat inspection in pigs from the same herd and batch.

From 165 herds, around 30 sets of lungs were collected at slaughter, and post mortem examination was performed at DPRC. The prevalence of chronic pleuropneumonia was considered an indicator of the within-herd prevalence of pigs undergoing a late App-like infection. The meat inspection recording ‘chronic pneumonia or lung abscesses (aerogenic)’ was considered the equivalent to chronic pleuropneumonia and an estimate of the prevalence of App-like infections found at meat inspection. Hence, the prevalence of ‘chronic pneumonia or lung abscesses (aerogenic)’ was extracted for the entire batch of pigs from which the lung sets originated. Then, the Spearman correlation coefficient between the two prevalence measures was estimated.

The median herd prevalence of pleuropneumonia found at DPRC was 3.3% (Q1-Q3: 0.0-9.1), whereas the corresponding median herd prevalence recorded at meat inspection was 0.0% (Q1-Q3: 0.0-0.6). The difference was highly significant (p< 0.0001). A significant (p=0.013) Spearman´s correlation coefficient of 0.19 was estimated.

The prevalence of chronic pleuropneumonia was significantly higher at the post mortem examinations compared to the meat inspection recordings. Furthermore, the correlation coefficient between the two was low. Relying on routine meat inspection data for monitoring App-like infections would most likely result in an under-estimation of the occurrence of late App-outbreaks in a herd and can therefore not be recommended for diagnostic purposes.

Disclosure of Interest: G. Blach Nielsen Conflict with: Industrial PhD at MSD Animal Health, S. Saxmose Nielsen: None Declared, P. Astrup Conflict with: MSD Animal Health, J. Haugegaard Conflict with: MSD Animal Health.