Infiltration of macrophages in IBDV-infected bursa. SPF chickens were inoculated with 104EID50 of cIBDV or vIBDV and bursal tissues were collected at PID 3, 5 and 7. (A) Bursal sections from virus-free chickens (a, b and c; 20X), vIBDV-infected chickens (d, e, and f; 20X) and cIBDV-infected chickens (g, h, and i; 20X) were examined for the presence of macrophages by immunohistochemistry using anti-chicken macrophage antibody. Brown color indicated by arrow represents the positive staining. (B) Macrophage positive cells were counted (20X) at PIDs 3, 5 and 7. The values represent the mean ± SEM of 5 fields/bursa/chicken on designated PID. #Statistically significant differences between control and vIBDV- or cIBDV-infected groups (p < 0.05). *Statistically significant differences between vIBDV- and cIBDV-infected groups (p < 0.05).