Fig 7. Histopathological changes and virus titers in lungs and tracheae of infected SPF chickens.

a) Histopathology of representative infected SPF chickens. Lungs and tracheae were collected at 4 dpi and fixed in 10% formalin, embedded in paraffin, and sectioned. b) Infection of the isolates in chickens. We inoculated groups of chickens intranasally and via the conjunctiva with 10⁶ EID₅₀ of the virus. Tracheae and lungs were harvested on 3 and 5 dpi. Viral titers for the tracheal and lung homogenates were determined by endpoint titration in SPF-embryonated chicken eggs. Each patterned bar represents the viral titers from an individual chicken. The black-dashed horizontal line indicates the lower limit of detection. c) Tissue sections were inspected, and histopathological changes were scored as follows. For the tracheae, 0: normal; 1: congestion; 2: cilia loss; 3: little inflammatory cell infiltration; and 7: a lot of inflammatory cell infiltration. For the lungs, 0: normal; 1: congestion; 2: hemorrhage; 3: inflammatory cell infiltration in the bronchial submucosa; and 7: a lot of inflammatory cell infiltration in the bronchial submucosa and alveolus. Average values for three birds are shown. Data are representative of three independent experiments.