Physiological and hematological changes in chum salmon (Oncorhynchus keta) infected with erythrocytic necrosis virus

Graduation date: 1986Chum salmon (Oncorhynchus keta) were artificially\ud infected with erythrocytic necrosis virus (ENV) to study\ud the physiological and hematolgical consequences of ENV-infection.\ud Infected and control fish were held in\ud pathogen-free seawater and sampled weekly for five weeks.\ud Physiological tests included plasma cortisol, glucose,\ud protein, and osmolality, blood lactic acid, and liver\ud glycogen concentrations. In general, fish infected with\ud ENV had higher liver glycogen values, and lower plasma\ud glucose and blood lactic acid levels than control fish.\ud Hematological tests included red and white blood cell\ud (RBC and WBC) counts, hematocrits, blood hemoglobin\ud concentrations, and erythrocyte fragility. Infected fish\ud had lower RBC counts, hematocrits, and hemoglobin\ud concentrations, higher WBC counts, and more fragile\ud erythrocytes than control fish. Other blood parameters\ud calculated from the hematology data indicated that the\ud erythrocytes of infected fish had higher mean corpuscular\ud volumes, depressed mean corpuscular hemoglobin\ud concentrations, and slightly lower mean corpuscular\ud hemoglobin. Erythrocytic inclusions were observed in the\ud cytoplasm of RBC of infected fish, and unnucleated cells\ud were observed by week 2. In this experiment, severity of\ud infection progressed steadily through week 4, after which\ud the fish appeared to be recovering. In a second study,\ud fish were infected with ENV, held for three weeks, and\ud recovery from exercise was measured. Plasma glucose and\ud osmolality were higher in infected fish, while plasma\ud cortisol and blood lactate levels were only slightly\ud elevated. These studies indicate that chum salmon were\ud able to withstand the effects of ENVinfection without\ud irreversible physiological consequences. However, when\ud subjected to-exercise, infected fish recovered more\ud slowly than controls and seemed to have increased\ud osmoregulatory difficulties