Isolation and initial characterization of new betanodaviruses in shellfish

Area of Science:

• Aquatic Animal Health
• Virology
• Molecular Biology

Background:

• Betanodaviruses are known pathogens causing viral nervous necrosis (VNN) in finfish.
• Current detection methods primarily focus on finfish VNN outbreaks.

Purpose of the Study:

• To identify and characterize novel betanodaviruses in shellfish.
• To determine the phylogenetic relationship and pathogenicity of the newly identified virus.

Main Methods:

• Utilized semi-nested two-step RT-PCR (DSN-2 RT-PCR) and discriminative multiplex two-step RT-PCR (DMT-2 RT-PCR) for detection.
• Performed virus isolation, electron microscopy, phylogenetic analysis, and experimental infection tests.
• Conducted histopathological examination and prevalence surveys in shellfish samples.

Main Results:

• Identified a new betanodavirus, Korean shellfish nervous necrosis virus (KSNNV), in shellfish samples.
• Phylogenetic analysis revealed KSNNV forms a distinct cluster, separate from known betanodavirus genotypes.
• Experimental infections showed KSNNV can infect fish species, causing brain vacuolation but no mortality or clinical signs, with lower viral loads than RGNNV.

Conclusions:

• KSNNV represents a new genotype of betanodavirus, primarily associated with shellfish.
• While not causing overt disease in finfish, KSNNV induces neurological changes, warranting further investigation into its ecological role and potential impact.