Fig. 2

Pathological sections (H&E staining) and immunohistochemical analysis of trachea and bronchus. A: lungs (100 ×), alveolar septum thickening (green arrow), macrophages (black arrow); B: lungs (400 ×), alveolar epithelial cell necrosis (green arrow), fibrinoid exudation (blue arrow), lymphocytes (yellow arrow), telangiectasia (purple arrow); C: submandibular lymph nodes (400 ×), necrotic lymphocytes (yellow arrow), fibrinoid exudation (blue arrow), bronchus (400 ×), mucosal epithelial necrosis and exfoliation (green arrow), inflammatory cell infiltration (red arrow). Immunohistochemistry analysis; D: Trachea (400×), E: Bronchus (400×), the nucleus in the image is displayed blue, and the positive signal of M. ovipneumoniae is displayed in brownish yellow