The first detection of betanodavirus reassortant genotype (RGNNV/SJNNV) isolated from gilthead sea bream (Sparus aurata) in the Turkish coastlines: The importance of screening and monitoring studies for identifying the source of the infection.

Viral nervous necrosis (VNN) is now endemic in the Mediterranean basin and the RGNNV genotype betanodavirus has caused frequent epidemics in European sea bass for a long time. Unexpected and increasing VNN epidemics have been reported in gilthead sea bream (GSB) farms in the last few years, from which the RGNNV/SJNNV genotype has been mostly isolated. The aim of this study was to perform a molecular characterization of the betanodavirus isolated from GSB (weighing 90-100 g) in a marine fish farm in the Aegean Sea and also, as an early warning exercise, to investigate the presence/absence of the virus in associated nearby farms (n:20) and in hatcheries (n:3). No virus was detected in any of the nearby farms or two hatcheries. However, in one hatchery, betanodavirus was detected in a 160-day-old GSB. The identified betanodavirus was genotyped as reassortant RGNNV/SJNNV and was phylogenetically related to the virus detected in the farm located in the Aegean sea. There have been multiple detections of the RGNNV genotype in Turkish coastal waters; however, the RGNNV/SJNNV genotype has been detected for the first time and it should be an early warning to focus attention on betanodaviruses in Turkish aquaculture.

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.

Molecular characterization of G and F protein genes of bovine respiratory syncytial virus detected from dead calves caused by severe respiratory syndrome: emergence of novel mutations and their importance.

Bovine respiratory syncytial virus (BRSV) is an important viral agent in bovine respiratory disease complex affecting young calves from asymptomatic to fatal. Although BRSV is widely prevalent in Türkiye as in other parts of the world, there are limited molecular studies on BRSV in Türkiye. Therefore, in order to better understand the characteristics of circulating BRSV in Türkiye, a study based on the molecular analysis of both F and G proteins was performed. For this purpose, the presence of BRSV was investigated in 20 calves that died as a result of severe respiratory syndrome in the western region of Türkiye in 2020. Nested PCR was performed for both gene regions, and the products were sequenced. Four samples detected as BRSV positive were identified as genotype III according to both gene regions in molecular analysis. However, they were separated into two distinct clusters due to significant differences in nucleotide (90.09-99.54%) and amino acid (85.42-99.31%) similarities between them. Besides, two positive samples in the same cluster were even more different from previously detected Turkish isolates (90.78-92.17% nt and 87.50-89.58% aa). More over, we detected nine novel aa mutations in the extracellular domain, an immunologically important region in the G protein of the virus, that have not been reported in other world isolates found in Genbank until now. These findings suggest that there may be many different viruses in circulation that have the ability to escape the immune system. We recommend that these findings be taken into account in planning both vaccine and epidemiological studies. Supplementary Information: The online version contains supplementary material available at 10.1007/s13337-023-00846-7.