Daesub Song*
1, Bokyu Kang*
1, Chulseung Lee*, Linda J. Saif†, Gunwoo Ha‡, Dongseok Kang‡, Seongjun Park§, Bongkyun Park§, and Jinsik Oh‡
Figure 3. Histopathologic lesions in the trachea and lungs of control (A and C) or experimentally infected (B, D–F) dogs (A/canine/Korea/01/2007 [H3N2]) at different days postinoculation (dpi). A) Control dog at 9 dpi, showing normal pseudostratified columnar epithelium lining of the trachea; original magnification ×400. Hematoxylin and eosin (HE) stain. B) Influenza-infected dog at 9 dpi, showing necrotizing tracheitis characterized by necrosis (n), squamous metaplasia (s), and hyperplasia of the epithelium and nonsuppurative inflammation (c) in the connective tissue; original magnification ×400. HE stain. C) Control dog at 3 dpi, showing normal alveoli; original magnification ×200. HE stain. D) Influenza-infected dog at 3 dpi, showing severe diffuse necrotizing bronchitis and bronchiolitis with suppurative inflammation in the lumina; original magnification ×100. HE stain. E) Influenza-infected dog at 6 dpi, showing severe necrotizing bronchiolitis; original magnification ×200. HE stain. F) Influenza-infected dog at 6 dpi (serial section of E), showing large amounts of influenza A virus antigens (red stain; arrows) in the bronchiolar epithelium and lumen. Immunohistochemistry; Red Substrate (Dako, Carpinteria, CA, USA); Mayer’s hematoxylin counterstain. G) Influenza-infected dog at 9 dpi, showing severe necrotizing alveolitis with accumulation of necrotic cells in terminal bronchioles (tb) and alveoli (a); original magnification ×200. HE stain.