The multifaceted challenge of viral nervous necrosis in fish farming: a review of current knowledge and control

Viral nervous necrosis (VNN), caused by the nervous necrosis virus (NNV) of the genus Betanodavirus, is a significant threat to global aquaculture, resulting in substantial economic losses in both marine and freshwater fish farming. The virus demonstrates considerable genetic diversity, encompassing multiple genotypes and reassortant strains that affect host susceptibility and disease severity across a wide array of fish species. Environmental factors strongly influence viral transmission and outbreak dynamics. Advances in diagnostic methodologies have enhanced the speed and sensitivity of detection. Although commercial vaccines are available for selected host species and production settings, their availability remains limited across fish species, viral genotypes, geographic regions, and early developmental stages. This review summarizes the current knowledge on Betanodavirus virology, host tropism, epidemiology, molecular diagnosis, microbiome, and control. Furthermore, it focuses on advanced disease manipulation via the microbiome and emerging molecular diagnostic platforms.