Histopathologically, multifocal coagulation necroses characterized by acellular homogenous eosinophilic appearance and mononuclear cell infiltrations surrounded necrotic cell debris. In severe cases, widespread hemorrhages showed association with hepatic necroses. Hepatocytes mostly showed parenchymatous degeneration, cytoplasmic swelling and they had clear, hyperchromatic nuclei. In some nuclei of the hepatocytes, intranuclear basophilic viral inclusions were observed (Figure 2). In kidneys, multifocally localized interstitial lymphocytes and plasma cell infiltrations in the cortex, tubular hydropic degenerations were detected. In two cases, interstitial pnemonia, alveolar epithelia hyperplasia, and bronch/iolitis were seen. In proventriculus mucosae, numerous heterophilic leucocyte infiltrations were present in the submucosae. FAdV-4 antigen specific immunoreactions were observed in degenerated hepatocytes and in the necrotic areas, kidney tubul epithelia, interstitital inflammatory cells and in urethelial epithelia, alveolar and bronchial epithelia in the lungs.
FIGURE 2. a) Severe coagulation necrosis, homogeneous eosinophilic appearance and some structural remnants of hepatic cords were visible but the hepatocytes were completely necrotic (arrows). At the periphery, focal lymphocyte and macrophage accumulations (arrow heads) were seen in the liver, H&E, Bar= 300 μm.
b) Clear nucleus due to characteristic circular margination of the chromatin in the hepatocytes. Some degenerated hepatocytes had basophilic intranuclear viral inclusions (arrow heads and inset). Liver, Hematoxylin-eosin, Bar= 45 μm.
c) Hydropic degeneration and necrosis of the cortical tubule epithelia, and in healthy tubular epithelia nuclei seemed clearbut contained numerous intranuclear basophilic inclusions. Hematoxylin-eosin, Bar= 90 μm.
d) FAdV-4 antigen immunopositive reactions, red dots, in the necrotic areas and degenerated hepatocytes (arrowheads). Avidin biotin complex immunoperoxidase test, FAdV-4 antibody, Gill’s hematoxylin counterstaining, Bar= 180 μm.
e) Immunoperoxidase positive reactions in the degenerative and necrotic tubule epithelia of the kidney. Avidin biotin complex immunoperoxidase test, FAdV-4 antibody, Gill’s hematoxylin counterstaining, Bar= 180 μm.
f) Strong viral antigen immunopositivity on the bronchiolar epithelia (arrowheads= and alveolar walls. Avidin biotin complex immunoperoxidase test, FAdV-4 antibody, Gill’s hematoxylin counterstaining, Bar= 300 μm.