Development towards an experimental protocol for the transmisson of pancreas disease of Atlantic salmon Salmo salar

Abstract

The w ~ d e s p r e a d loss of exocnne pancreas secretory aclnai cells, slmllai to the pathology observed In Atlantic salmon Salmo salaraffected by pancreas dlsease, was reproduclbly transmitted to salmon parr in fresh water by intraperltoneal injections of homogenised k ~ d n e y and spleen removed from affected f ~ s h . In fresh water the prevalence of pancreas pathology in experimental populat~ons in-creased to a maximum of 40 to 70 U/;) over 2 to 4 wk followed by an apparent recovery w ~ t h l n a further 4 w k . In sea water fish the incidence of affected salmon was lower and the temporal pattern of progres-slon more varied than was the case In fresh water Infectious pancreatic necrosis virus was not detected in experimental fish or homogenised fish t~ssues. In both fresh and sea water the lncldence of the pan-creas pathology was dependent upon the dose of homogenate injected. Preliminary results indicate that experimentally affected fish in sea water are less likely to feed than non-affected fish. Evldence supporting a n infectious cause of the pancreas pathology ~ n c l u d e d : flnd~ngs consistent with the I-epll-cation of the causative agent in fish tissue, transmission to salmon cohabited with affected animals and no dim~nution in the effectiveness of homogenates in transmitting the pancreas pathology after 0.22 p m filtration