Molecular Characterization of Novel Fish Viruses from Technical Assistance Cases

Science Center Objects

Viruses occur in many cultured and wild stocks of fish. William Batts collaborates with many government, state, tribal, and private research and diagnostic laboratories to aid in identification of these unknown replicating agents of uncertain pathogenicity. Typically, viruses can be replicated in a variety of fish cell lines and investigated at several temperatures to see if the cytopathic effect is different from existing fish viruses. When they are unknown to the diagnosticians, the viruses are sent to the Western Fisheries Research Center in Seattle for attempts at characterization.

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Gizzard shad infected with viral hemorrhagic septicemia virus

Gizzard shad infected with viral hemorrhagic septicemia virus in the Great Lakes. Photo taken in Spring of 2017. (Credit: Gary Whelan, Michigan Department of Natural Resources. Copyright 2009)

Bullet-shaped rhabdovirus particles

Bullet-shaped rhabdovirus particles are budding out of a fish cell membrane; virus was initially isolated from an asymptomatic starry flounder in March 2000 in northern Puget Sound. Electron microscopy photo prepared by Carla Conway, Dr. Emil Chi, and Mechthild Jonas at the University of Washington. (Public domain.)

Often unknown viruses are an existing strain of virus that was simply unfamiliar to the diagnostic lab, perhaps due to this virus never being isolated in the geographic region or in the fish species being investigated. However, the technical assistance service we provide has led to scientific publications on a wide variety of fish viruses including novel members of orthomyxoviruses, aquareoviruses, picornaviruses, nidoviruses, hepeviruses, paramyxoviruses, and rhabdoviruses.

We use amplification of the viral nucleic acids by the polymerase chain reaction (PCR) to obtain sufficient DNA for molecular sequencing. This authentic DNA sequence is used to search for existing viral sequences accessioned into DNA databases. If no virus match occurs, it is possible that the agent is quite unique, never observed before in any fish population.