Edwardsiellosis in farmed rainbow trout (Oncorhynchus mykiss)

摘要

Edwardsiella tarda was isolated from naturally infected rainbow trout (Oncorhynchus mykiss) in raceway culture on a commercial fish farm where the fish were kept at a density of 110?kg?m?3 and at a water temperature of 14°C and with a photoperiod of 13?h light:11?h dark. The clinical signs of diseased fish (150?±?20?mm standard length) were anorexia and lethargy. The most striking lesions in the fish were in the liver. There were hyperaemia and haemorrhages; on histopathological examination, the liver displayed inflammatory infiltrate in portal area, focal necrosis, dilatation of blood sinus and activation of sinusoidal cells. Infection experiments, performed 2?years after isolation of the original culture of E. tarda, were carried out under laboratory conditions at water temperatures of 15, 18 or 24°C. All experimental fish (common carp, Prussian carp, tench), intraperitoneally injected with 8?×?106 cells, demonstrated a total resistance to E. tarda.