DEVELOPMENT TOWARDS AN EXPERIMENTAL PROTOCOL FOR THE TRANSMISSION OF PANCREAS DISEASE OF ATLANTIC SALMON SALMO-SALAR

The widespread loss of exocrine pancreas secretory acinar cells, simil ar to the pathology observed in Atlantic salmon Salmo salar affected b y pancreas disease, was reproducibly transmitted to salmon parr in fre sh water by intraperitoneal injections of homogenised kidney and splee n removed from affected fish. In fresh water the prevalence of pancrea s pathology in experimental populations increased to a maximum of 40 t o 70 % over 2 to 4 wk followed by dn apparent recovery within a furthe r 4 wk. In sea water fish the incidence of affected salmon was lower a nd the temporal pattern of progression more varied than was the case i n fresh water. Infectious pancreatic necrosis virus was not detected i n experimental fish or homogenised fish tissues. In both fresh and sea water the incidence of the pancreas pathology was dependent upon the dose of homogenate injected. Preliminary results indicate that experim entally affected fish in sea water are less likely to feed than non-af fected fish. Evidence supporting an infectious cause of the pancreas p athology included: findings consistent with the replication of the cau sative agent in fish tissue, transmission to salmon cohabited with aff ected animals and no diminution in the effectiveness of homogenates in transmitting the pancreas pathology after 0.22 mum