ABSTRACT
This chapter presents a synopsis of what is known about the viruses, starting with their isolation and pathogenicities, and then discusses the relatedness of the viruses on the basis of their structural and known antigenic properties. Fish virology is relatively recent; the first virus isolation being reported in 1960. In a broad sense, the four rhabdoviruses are classified into two major divisions reflecting the origin of the various agents: the salmonid fish rhabdoviruses and the nonsalmonid fish rhabdoviruses. Infections of rainbow trout by viral hemorrhagic septicemia or Egtved viruses are seasonal in occurrence. In the case of Oregon sockeye disease virus, the disease occurs in both the anadramous sockeye salmon and in Kokanee salmon, its landlocked form. Roegner-Aust and associates in 1950 first suggested that the etiologic agent of the infectious dropsy disease of carp was a virus, on the basis that viruslike particles in organs taken from diseased carp could be observed by electron mcroscopy.
