VPP 322: Aquatic Animal Diseases, Health Care and Management (1+1)

Histopathological changes caused due to viral pathogens in fishes

HISTOPATHOLOGICAL CHANGES DUE TO VIRAL PATHOGENS IN FISHES

Reported histopathological changes caused due to viral pathogens in fishes

Viral disease	Histopathological changes
Infectious haematopoietic necrosis viral disease	Degeneration of gill lamellae. Edema, ascites, gastrointestinal tract filled with translucent mucoid fluid. Sometimes petechiation of visceral fat, mesenteries, peritoneum,swim bladder, meninges, pericardium and skeletal muscle. Lesions may be absent in cases of sudden mortality. Severe necrosis of hematopoietic tissue of the spleen and the kidney. Intracytoplasmatic and intranuclear inclusions in the acinar and islet cells of the pancreas. Focal necrotic changes can occur in the liver. Necrosis of granular cells in the alimentary tract is typically seen in fish 3 - 4 month old. Anterior kidney and spleen show focal areas of cellular degeneration and necrosis. Intracytoplasmatic droplets can be seen in kidney tubule epithelium cells. Kidney imprints show necrotic bodies. Moderate sloughing of the epithelial lining of the small intestine.
Infectious pancreatic necrosis viral disease	Necrosis extending throughout the pancreas. Inclusion bodies are visible in the cytoplasm. There can be a variable inflammatory response to the pancreatic acinar cell necrosis, varying from a mild mononuclear cell infiltrate to severe post-necrotic fibrosis involving all of the surrounding mesenteric fat.
Lymphocystis  Iridovirus of genus Lymphocystivirus	Clump of lymphocystis cells produced on the skin. The cells contain large nuclei, and inclusion bodies are evident in the cytoplasm.