California-Nevada Fish Health Center
Pacific Southwest Region


Viruses are obligate, submicroscopic, intracellular parasites that depend upon living cells for their reproduction and cannot propagate in the absence of living cells. All known viruses are infective agents, are often host specific, and in some cases have a high specificity for certain tissues. The isolation and identification of viruses is an elaborate process and requires sophisticated equipment. New methods continue to be developed, but there are several standard techniques used for laboratory diagnosis of viral infections. Many methods utilize in vitro cell culture (tissue culture) systems which are susceptible to cytopathological effects (CPE) from the virus and molecular techniques for confirmation.

As there are no effective treatments for viral infections of hatchery fish; regular monitoring of juvenile and adults, sanitation and disinfection are the only practical methods of control.

Last updated: June 18, 2014