Histopathology in different tissues of H5N1-infected pika. (A, C, E, G, I, K): Representative specimen from the uninfected control group (n = 5, control group; n = 5 per infected group). (B, D, F, H, J, L): Representative specimen from the H5N1-infected group. (A) Uninfected Trachea. (B) Desquamation of the apoptotic tracheal epithelial cells was observed in the virus-infected trachea (arrow). (C) Uninfected ileum. (D) No notable abnormalities were observed in the ileum from the infected pika. (E) Uninfected liver. (F) No significant abnormalities were observed in the liver from the infected pika. (G) Uninfected kidney. (H) Lymphocytic infiltrations around glomerular afferent arterioles in the kidney (arrows). (I) Uninfected cerebellum. (J) Apoptotic Purkinje cells were observed in the infected cerebellum (arrows). (K) Uninfected spleen. (L) Enlarged white pulps were observed in the virus-infected spleen (arrows). Bar, 50 μm.