Detection of RGNNV genotype betanodavirus in the Black Sea and monitoring studies

Viral nervous necrosis (VNN), caused by betanodavirus, is a significant viral infection that threatens marine aquaculture. Freshwater and marine fish farms in Turkey are subjected to annual pathogen screenings. In 2016, during the Nervous Necrosis Virus screening program conducted in the Black Sea, betanodavirus was unexpectedly detected using real-time reverse transcription-polymerase chain reaction in apparently healthy sea bass. Phylogenetic analysis of both the RNA1 and RNA2 segments of the virus determined that the betanodavirus detected was red-spotted grouper nervous necrosis virus genotype (RGNNV). Following the initial discovery of betanodavirus in the Black Sea, monitoring studies performed over a 3 yr period have not indicated any additional presence of the virus. The absence of clinical symptoms related to VNN disease in the area's marine fish farms and the surrounding detection zone, and the fact that the virus has not been detected anew in monitoring programmes conducted following the initial detection, indicate that there is no virus circulation in the detection zone.

Automated summary

Betanodavirus, specifically the red-spotted grouper nervous necrosis virus genotype, was unexpectedly detected using real-time reverse transcription-polymerase chain reaction in apparently healthy sea bass in the Black Sea in Turkey. Despite initial detection, subsequent monitoring studies over a 3-year period showed no additional presence of the virus and no clinical symptoms related to VNN in marine fish farms in the area.