Experimental reproduction of porcine respiratory disease complex in pigs inoculated porcine reproductive and respiratory syndrome virus and Mycoplasma hyopneumoniae and followed by inoculation with porcine circovirus type 2

Abstract

The aim of this study was to reproduce severe pneumonic lesions, similar to those during naturally-occurring porcine respiratory disease complex, in pigs dually inoculated with porcine reproductive and respiratory syndrome virus and Mycoplasma hyopneumoniae at 6 weeks of age, followed by inoculation with porcine circovirus type 2 at two weeks after. Time and sequence of infection with three pathogens mirror Asian field conditions. Microscopically, interstitial pneumonia and peribronchiolar lymphoid hyperplasia are considered the most characteristic lung lesions in infected pigs. The results of the present study demonstrate that inoculation of pigs with these three pathogens can lead to severe interstitial pneumonia with peribronchial or peribronchiolar lymphoid hyperplasia and fibrosis.

Keywords: Mycoplasma hyopneumoniae; porcine circovirus type 2; porcine reproductive and respiratory syndrome virus.

Fig. 1.

Photomicrograph of lung showing severe mottled-tan consolidation. Bar=50 µm.

Fig. 2.

Photomicrograph of section of lung showing severe markedly thickened by type 2 pneumocyte hypertrophy and hyperplasia in alveolar septa, and severe infiltration with macrophages, necrotic macrophages, and multinucleated cells in alveolar spaces. Hematoxylin and eosin (H&E) staining. Bar=50 µm (A). Photomicrograph of section of lung showing moderate-to-severe peribronchiolar lymphohistiocytic cuffing and nodular formation. H&E staining. Bar=50 µm (B).

Fig. 3.

Photomicrograph of section of lung showing porcine reproductive and respiratory syndrome virus nucleic acids in alveolar septa. In situ hybridization, Bar=50 µm (A). Photomicrograph of section of lung showing Mycoplasma hyopneumoniae nucleic acids (arrows) in surface of epithelial lining cells in bronchiole. In situ hybridization, Bar=50 µm (B). Photomicrograph of section of lung showing porcine circovirus type 2 antigens in alveolar septa. Immunohistochemistry, Bar=50 µm (C).