Further evidence for a viral etiology in plasmacytoid leukemia of Chinook salmon Oncorhynchus tshawytscha

Plasmacytoid leukemia (PL) is an important disease of seawater pen-reared chinook salmon Oncorhynchus tshawytscha in British Columbia, Canada.The disease is caused by a n infectious agent, and the microspondium Enterocytozoon salmonis, Renibacterium salmoninarum (the cause of bacterial kidney disease.BKD), and a retrovirus have been suggested as possible causes.Experimental transmission studies were conducted to elucidate the etiology of PL and they strongly indicate that a virus is the cause of the disease.The disease was transmitted using an inoculum prepared from affected kidney and spleen that had been passed through a 0.22 Fm filter.Oral treatment with Fumagillin DCH. an antiprotozoan compound used in other studies to treat E. salrnonis infection, had no effect on the disease.Injection of R. salmoninarum that was isolated from a fish with PL caused BKD and no signs of PL.