The IL-1β mRNA expression levels in the FAdV-only group were significantly higher than those in the control group at 3 and 5 dpi with FAdV-4-HB1501 (p < 0.05), while this level in the IBDV-FAdV co-infection group was considerably higher than that in the control group at 5 dpi with FAdV-4-HB1501 (p < 0.05). This evidence concerns the gene IL1B and coinfection.