Reservoirs of Red-Spotted Grouper Nervous Necrosis Virus (RGNNV) in Squid and Shrimp Species of Northern Alboran Sea

Abstract

The production of the aquaculture industry has increased to be equal to that of the world fisheries in recent years. However, aquaculture production faces threats such as infectious diseases. Betanodaviruses induce a neurological disease that affects fish species worldwide and is caused by nervous necrosis virus (NNV). NNV has a nude capsid protecting a bipartite RNA genome that consists of molecules RNA1 and RNA2. Four NNV strains distributed worldwide are discriminated according to sequence homology of the capsid protein encoded by RNA2. Since its first description over 30 years ago, the virus has expanded and reassortant strains have appeared. Preventive treatments prioritize the RGNNV (red-spotted grouper nervous necrosis virus) strain that has the highest optimum temperature for replication and the broadest range of susceptible species. There is strong concern about the spreading of NNV in the mariculture industry through contaminated diet. To surveil natural reservoirs of NNV in the western Mediterranean Sea, we collected invertebrate species in 2015 in the Alboran Sea. We report the detection of the RGNNV strain in two species of cephalopod mollusks (Alloteuthis media and Abralia veranyi), and in one decapod crustacean (Plesionika heterocarpus). According to RNA2 sequences obtained from invertebrate species and reported to date in the Mediterranean Sea, the strain RGNNV is predominant in this semienclosed sea. Neither an ecosystem- nor host-driven distribution of RGNNV were observed in the Mediterranean basin.

Detection of Human and Fish Viruses in Marine Gastropods

“…Despite the fact that RGNNV is a well-known finfish pathogen, its presence in invertebrates has been frequently reported too. In particular, it has been identified in several species of bivalve molluscs [ 8 , 11 , 41 ], cephalopods [ 12 , 13 , 42 ] and crustacea [ 13 , 41 , 43 ]. The presence of RGNNV in invertebrates has not been associated, thus far, with any pathological finding.…”

“…Betanodaviruses are reported in a growing number of other invertebrate species such as cephalopods [ 12 , 13 ] and gastropods [ 14 ]. In particular, as regards gastropods, currently, they have only been reported once in the red-mouthed rock shell ( Stramonita haemastoma ) belonging to the Muricidae family [ 14 ].…”

Integrated Management Strategies for Viral Nervous Necrosis (VNN) Disease Control in Marine Fish Farming in the Mediterranean

“…Betanodavirus were also detected in marine invertebrates using molecular techniques [ 27 , 28 , 29 , 30 ]. The potential risk associated with the presence of betanodaviruses in marine invertebrates such as bivalves or polychaetes should not be disregarded but, in this case, invertebrates should be considered as vectors, potentially associated with filtration activity of some of these organisms [ 31 ].…”

Detection of different Betanodavirus genotypes in wild fish from Spanish Atlantic coastal waters (Galicia, northwestern Spain)

“…Since the 2000s, the number of epidemiological surveys on NNV prevalence has increased substantially, reporting the presence of the virus in several species of marine vertebrates and invertebrates. Most of these studies have been conducted in Asian countries (Gomez et al 2004(Gomez et al , 2006(Gomez et al , 2008aBaeck et al 2007;Sakamoto et al 2008;Liu et al 2015;Ma et al 2015;Kim et al 2018;Banu et al 2019); the Mediterranean region (Toffolo et al 2007;Panzarin et al 2012;Volpe et al 2018;Bitchava et al 2019;Errani et al 2021;Johnstone et al 2022); and, to a lesser extent, coastal waters of Nordic countries (Nylund et al 2008;Korsnes et al 2017). In this study, we conducted an NNV survey to determine NNV prevalence in wild fish captured along the northwestern Atlantic coast of Spain, an area in which no NNV detections have been reported to date.…”