Evaluation of Lung Scoring System and Serological Analysis of Actinobacillus pleuropneumoniae Infection in Pigs

Actinobacillus pleuropneumoniae (A. pleuropneumoniae) is a respiratory pathogen that causes a great economic loss every year in the swine industry worldwide. The objective of this study was to investigate the prevalence of pleuritis in central Taiwan using the slaughterhouse pleurisy evaluation system (SPES) and to evaluate the correlations among SPES, serum antibody (ApxI/Tbp2) positivity, and the presence of apxIVA in lung tissue caused by A. pleuropneumoniae. Lung and blood samples were collected randomly from the slaughterhouse. The pleuritis lesions were morphologically evaluated for a SPES score and then examined the positive rate of apxIVA by PCR, and the blood samples were analyzed by ELISA. The positive rate of the samples we collected from slaughterhouse indicated that the prevalence of A. pleuropneumoniae in central Taiwan measured by SPES, ELISA, and PCR was 21.2, 40.6 and 23.7%, respectively. Generally, the positive rate of serum antibody and apxIVA detection increased when SPES values rose. However, the lungs with SPES 4 presented a low ApxI/Tbp2 antibody titer in the sera, and that would be considered as a secondary infection of A. pleuropneumoniae because the lesion is usually accompanied by extensive polyserositis. In conclusion, according to cross-comparison and statistical analysis of our data, the serum antibody levels were strongly correlated with SPES, which promises a fast and useful evaluation tool for clinical investigation of A. pleuropneumoniae infection. (C) 2017 PVJ. All rights reserved