ABSTRACT
Infectious hematopoietic necrosis (IHN) is a highly contagious viral disease primarily of rainbow trout and Pacific salmon. The etiological agent of IHN is a rhabdovirus, infectious hematopoietic necrosis virus (IHNV). The clinical signs may vary somewhat from species to species. The larger fish in an infected population of the same age usually exhibit clinical signs before smaller fish. Clinical IHN is diagnosed by isolation of the virus in cell culture using conventional methods. Whole fry, or viscera of fingerlings, are suitable for virus isolation. Pathogenesis studies by W. T. Yasutake and D. F. Amend confirmed that the target tissue of IHNV was the hematopoietic portion of the kidney, where they found a close correlation between histopathological progression and virus concentration. Infectious pancreatic necrosis virus infects a wide range of fish species. In trout, presumptive clinical diagnosis of infectious pancreatic necrosis is made based on mortality patterns and clinical signs.
