Cytopathology and Coagulopathy Associated with Viral Erythrocytic Necrosis in Chum Salmon

The 8-month cytopathologic progression of viral erythrocytic necrosis (VEN) disease in chum salmon Oncorhynchus keta is described. Single to multiple acidophilic, cytoplasmic viral inclusion bodies developed first in mature erythrocytes and then, within 1–2 months, all morphologically identifiable hemopoietic cell types contained VEN inclusions. Cytologic analysis indicated that multinucleate giant erythroblasts, ineffective erythropoiesis, and abnormal erythroid cell maturation occurred. A significant increase in blood coagulation time occurred concomitantly. This severe and chronic blood dyscrasia accounts for some of the pathophysiologic sequelae previously observed.