Viral causes of respiratory diseases in piglets: Emphasis on PCV2, PRSV and SIV

The main objective of this study was to investigate the existence of histopathological lung lesions that attribute to viral respiratory infection, namely, porcine circovirus type 2 (PCV2), porcine reproductive and respiratory syndrome virus (PRRSV), and swine influenza virus (SIV) in formalin fixed and paraffin embedded archival lung tissues stained with haematoxylin and eosin (H&E). Selection of the lung tissues for histopathology was based on clinical symptoms, macroscopic lesions encountered at necropsy and results of in situ hybridization (ISH), polymerase chain reaction (PCR) and/or immunohistochemistry (IHC) conducted earlier. Characteristic lung lesions were observed in all tissues that were confirmed positive earlier, including necrotizing bronchiolitis in one lung tissue of a SIV suspected case.