Pathological observations of porcine respiratory disease complex (PRDC) in the wild boar (Sus scrofa)

Abstract

Porcine respiratory disease complex (PRDC) is a multifactorial respiratory syndrome related to the infection with different pathogens. Although most of these pathogens have been detected in the wild boar, the PRDC pneumonic lesions in this species have not been characterized. The aims of this study were to assess the presence of the main swine respiratory pathogens in wild boar populations from mid-western Spain and to describe the pathological features present in the lung from animals infected with PRDC pathogens. A pathological assessment based on five histological parameters was carried out in lung sections from 210 hunted wild boar. The presence of Mycoplasma hyopneumoniae, Haemophilus parasuis, Actinobacillus pleuropneumoniae, Pasteurella multocida, Aujeszky’s disease virus, and porcine circovirus type 2 (PCV2) in lungs was assessed by the use of specific PCR assays. Additionally, immunohistochemical techniques were carried out to detect swine influenza virus (SIV) and porcine reproductive and respiratory syndrome virus (PRRSV) infection in the lungs. Furthermore, the distribution of infected cells with PCV2 and the presence of M. hyopneumoniae throughout the pulmonary parenchyma were evaluated using immunohistochemistry and in situ hybridization assays in a subset of animals. Wild boar infected with M. hyopneumoniae, H. parasuis, or P. multocida showed the most severe lesions. M. hyopneumoniae, SIV, PCV2, and PRRSV were detected in single or mixed infections. Animals suffering from mixed infections with M. hyopneumoniae together with different viruses showed severe bronchopneumonia associated with interstitial pneumonia, suggesting that interactions between pathogens might increase the severity of pathological outcomes.