Marine organisms serve as hosts for a diversity of parasites and pathogens. Mortalities affect not only the host population, but can cascade through ecosystems (Ward & Lafferty 2004). In the past few decades, there has been a worldwide increase in reports of diseases affecting marine organisms of different taxa (Harvell et al. 1999). The aim of this study is to survey and investigate the presence of nervous necrosis virus (NNV) in wild marine fish and to determine the possibility of disease transmission between fish in the wild and mariculture fish. RNA viruses cause some of the most devastating diseases affecting the global aquaculture and mariculture industries (Lang et al. 2009). Nervous necrosis virus (NNV), an RNA virus belonging to family Nodaviridea, is the causative agent of viral nervous necrosis (VNN) - a diseases that affects marine fish worldwide, causing the highest ecological and socio-economical impacts in European farmed finfish (Gomez-Casado et al. 2011). VNN is globally distributed and already recognized in more than 100 finfish species. Some have proven to be susceptible to the disease while others are considered resistant to certain NNV genotypes but can serve as asymptomatic carriers such as Gilthead sea bream (Sparus aurata) - one of the most important species in the Mediterranean aquaculture (Toffan et al. 2017). Although wild fish are economically and ecologically important, prevalence of this pathogen in wild fish populations around the Levant Sea is basically unknown. To close this knowledge gap, wild fish species were sampled from four areas along the Israeli Mediterranean coast. RNA was extracted from brain, liver and kidney tissue of each fish, following reverse transcription PCR and real time PCR for the detection of NNV. Specific primers for both RNA1 and RNA2 were used to characterize the specific NNV strains. The compiled data will be used to assess viral transmission between different fish populations. Our preliminary results demonstrates prevalence rang of 0–17.4% positive tissue samples of different fish species that were tested and then confirmed by sequencing. Positive results found in several fish species from different locations suggests that NNV might be a widespread pathogen that can become a threat to wild fish populations and to cultured fish populations in the area.

* Presenting author

Literature Cited

1.  Ward JR, Lafferty KD. 2004. The elusive baseline of marine disease : are diseases in ocean ecosystems increasing? PLoS Biology. 2:0542–0547.

2.  Harvell CD, et al. 1999. Emerging marine diseases-climate links and anthropogenic factors. Science. 285(5433):1505–1510.

3.  Lang AS, et al. 2009. RNA viruses in the sea. FEMS Microbiology Reviews. 33(2):295–323.

4.  Gomez-Casado E, Estepa A, Coll JM. 2011. A comparative review on European-farmed finfish RNA viruses and their vaccines. Vaccine. 29(15):2657–2671.

5.  Toffan A, et al. 2017. Viral nervous necrosis in gilthead sea bream (Sparus aurata) caused by reassortant betanodavirus RGNNV/SJNNV: an emerging threat for Mediterranean aquaculture. Scientific Reports. 7:1–12.