Prevalence of Nervous Necrosis Virus and Streptococcus Species in Wild Marine Fish from the Eastern Mediterranean Sea
IAAAM 2019
Danny Morick1*; Ran Berzak2; Aviad Scheinin2; Dan Tchernov2,3
1Koret School of Veterinary Medicine, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel; 2Morris Kahn Marine Research Station, University of Haifa, Haifa, Israel; 3Department of Marine Biology, Leon H. Charney School of Marine Sciences, University of Haifa, Haifa, Israel


Marine organisms serve as hosts for a diversity of parasites, bacteria and viruses. In the last few decades, there has been a gradual increase in reports of diseases affecting marine organisms of different taxa1. The Mediterranean is an unusual sea, containing diverse marine fauna due to its variable geophysical and biogeographical properties in its different basins in different seasons, and therefore might serve as “test case” for the world’s oceans and can provide insight into larger scale marine ecosystems2. Its most eastern basin, the Levantine Basin, is an area in which there have been increases in both air and water temperature in the last two decades3,4. The abundance and prevalence of infectious diseases in marine animals have ecological, socio-economic and environmental impacts. Nervous necrosis virus (NNV) and Streptococcus iniae have come to be a major threat to marine aquaculture and have been detected in morbid marine organisms worldwide. However, despite their importance, there is lack of knowledge regarding those pathogens’ prevalence in wild fish species. From the eastern Mediterranean, indigenous and Lessepsian species from different trophic levels and different biological niches were sampled. A total of 174 fish and 32 crustaceans were tested for S. iniae and a total of 195 fish and 33 crustaceans were tested for NNV. We found an overall prevalence of 9.71% Streptococcus species and 21.49% NNV in selected marine fish and crustaceans by PCR and qPCR. Streptococcus iniae, a zoonotic agent, was detected in a higher prevalence in kidney compared to liver tissue, in positive fish samples. Co-infection of both pathogens was detected in only five specimens. We also examined gilthead sea bream (Sparus aurata) from an Israeli offshore marine farm during its grow-out period, in order to assess the possibility of horizontal pathogen transmission from wild fish to maricultured fish. Three out of 15 (20%) fish were found to be NNV positive after 120 days in the sea, suggesting spontaneous transmission from wild to farm fish. Our findings suggest that more of such surveys should be performed, especially in areas were mariculture farms are planned to be established.

* Presenting author

Literature Cited

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

2.  Lejeusne C, et al. 2010. Climate change effects on a miniature ocean: the highly diverse, highly impacted Mediterranean Sea. Trends in Ecology and Evolution. 25(4):250–260.

3.  Yeruham E, et al. 2015. Collapse of the echinoid Paracentrotus lividus populations in the Eastern Mediterranean--result of climate change? Scientific Reports. 5:134.

4.  Jeppesen E, et al. 2015. Ecological impacts of global warming and water abstraction on lakes and reservoirs due to changes in water level and related changes in salinity. Hydrobiologia. 750(1):201–227.


Speaker Information
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Danny Morick
Koret School of Veterinary Medicine, The Robert H. Smith Faculty of Agriculture, Food and Environment
The Hebrew University of Jerusalem
Rehovot, Israel

MAIN : Session 1: Infectious Diseases : Nervous Necrosis Virus & Streptococcus
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