Evidence of Natural Nervous Necrosis Virus Infection in Juvenile Greenfin Horse-Faced Filefish (Thamnaconus septentrionalis) During an Aquaculture Mortality Event
Year: 2026
Type: article
Abstract: Viral nervous necrosis (VNN), caused by nervous necrosis virus (NNV), is a devastating viral disease affecting marine fish aquaculture worldwide, particularly during larval and juvenile stages. Although NNV has a broad and expanding host range, the susceptibility of greenfin horse-faced filefish (Thamnaconus septentrionalis) has not been established. To determine whether T. septentrionalis is susceptible to NNV, we investigated an outbreak of abnormal mortality in juveniles from a marine aquaculture farm in Rizhao, Shandong Province, China. A comprehensive etiological investigation combined bacterial isolation and identification, real-time quantitative RT-PCR (RT-qPCR), tissue-distribution analysis, histopathology, transmission electron microscopy (TEM), and RNA2-based phylogenetic analysis. Diseased fish exhibited characteristic VNN-like neurological signs, including spiral swimming, loss of equilibrium, anorexia, and body darkening. Several bacterial taxa, including Vibrio- and Tenacibaculum-related isolates, were recovered from diseased fish, indicating the possibility of bacterial involvement. However, the concurrent detection of abundant NNV RNA in neural tissues, together with characteristic neurological signs, compatible histopathological lesions, and NNV-like particles, provided convergent evidence supporting natural NNV infection. NNV RNA was detected in all ten diseased fish, whereas the other screened viral pathogens were not detected. Pooled brain–eye samples contained 4.62 × 108 to 1.33 × 109 NNV RNA copies/μg total RNA, and abundant NNV RNA was also detected in brain, spleen, kidney, and trunk tissues. Histological examination showed vacuolar and degenerative lesions in the brain and retina, and TEM revealed numerous non-enveloped, spherical virus-like particles approximately 25 nm in diameter in neural tissues, consistent with NNV morphology. Phylogenetic analysis of the RNA2 capsid protein gene placed the detected virus within the RGNNV RNA2 lineage. Together, the neurological signs, NNV RNA detection, compatible histopathological lesions, NNV-like particles in neural tissues, and RNA2 phylogenetic evidence provide evidence of natural NNV infection in T. septentrionalis. These findings document evidence of natural NNV infection in T. septentrionalis under aquaculture conditions, highlight the need for further investigations into pathogenicity and transmission, and provide a basis for VNN surveillance and biosecurity management in filefish aquaculture.
Source: Pathogens
Language: English
Subfield: Immunology
Field: Immunology and Microbiology
Domain: Life Sciences
Open Access status: gold
Estimated APC paid: $2,654
OpenAlex ID: W7131908122