Comparative Pathogenicity of Three Strains of Infectious Bursal Disease Virus Closely Related to Poultry Industry

Figure 1. Clinical symptoms of IBD. (a) The mean symptomatic index (MSI) of HLJ0504 group. (b) The survival curve of chickens infected with different IBDV strains.

Figure 2. Gross lesions of the bursa. (a) The appearance of the bursa in each group from 48 h p.i to 14 d p.i. (b) Bursa to body weight ratio (B/BW). The B/BW ratios for each group at each time point were averaged over five chickens, except for the HLJ0504 group at 5 d p.i. to 7 d p.i. (n = 3) and 14 d p.i. (n = 1).

Figure 3. Histopathological changes of the bursa of group HLJ0504, SHG19, Gt, and Mock at 24 h p.i. (a–d), 36 h p.i. (e–h), 48 h p.i. (i–l), 3 d p.i. (m–p), and 7d p.i. (q–t).

Figure 4. Gross lesions of the spleen. (a) The appearance of the spleen in each group from 48 h p.i–14 d p.i. (b) Spleen-to-body weight ratio (S/BW). The S/BW ratios for each group at each time point were averaged over 5 chickens, except for the HLJ0504 group at 5 d p.i. to 7 d p.i. (n = 3) and 14 d p.i. (n = 1).

Figure 5. Gross lesions of the kidney (a–d), thymus (e–h), and proventriculus (i–l) of group HLJ0504, SHG19, Gt, and Mock. Pathological changes such as piebald in the kidney, thymus atrophy, and proventriculus hemorrhage were marked with arrows.

Figure 6. Electron microscopic observation of the infectious bursal disease virus (IBDV) in the bursa. (a) HLJ0504 group. (b) SHG19 group. (c) Gt group. The IBDV particles arranged in a lattice pattern were marked by a white arrow.

Figure 7. In vivo distribution and load of IBDV. (a) Bursa. (b) Spleen. (c) Thymus. (d) Caecal tonsil. (e) Kidney. (f) Heart. (g) Liver. (h) lung. (i) Blood. (j) Cloacal swab. The values for each group at each time point were averaged over three chickens, except for the HLJ0504 group at 14 d p.i. (n = 1). Treatments sharing different lowercase letter differ significantly at a confidence level (p < 0.05).

Figure 8. IBDV antibody titers in serum. The values for each group at each time point were averaged over five chickens, except for the HLJ0504 group at 7 d p.i. (n = 3) and 14 d p.i. (n = 1).

Figure 9. Inflammation-related genes expression in DT40 cells infected with different IBDV strains. The mRNA levels of IL-6 (a), IL-8 (b), IL-18 (c), NLRP3 (d), and caspase 1 (e) at 24, 36, 48, 60, and 72 h post-infection were detected by qRT-PCR. Treatments sharing different lowercase letter differ significantly at a confidence level (p < 0.05).