Detection of Red-spotted grouper nervous necrosis virus (RGNNV) in shrimp and squid of the Mediterranean Sea

Abstract

The quest for sustainable fisheries and procurement of food supply has increased aquaculture production up to the world fisheries capture. Viral encephalopathy and retinopathy (VER), also known as viral nervous necrosis (VNN), is caused by nervous necrosis virus (NNV) and results in high mortality of larvae and juveniles of continuous increasing amount of fish species. The disease causes vacuolation and necrosis of the central nervous system. The virus has a nude capsid protecting a bipartite RNA genome that consists of positive stranded molecules RNA1 and RNA2. Four NNV genotype strains distributed worldwide are discriminated according to sequence homology of the capsid protein encoded by RNA2. Preventive treatments prioritize the RGNNV (Redspotted grouper nervous necrosis virus) genotype that has the highest optimum temperature for replication and the broadest range of susceptible species. A flow of NNV between wild and cultured fish had been demonstrated, and reservoirs of NNV have been reported in invertebrates, raising concern on the spreading of NNV in the mariculture industry through contaminated food. The present study aimed to contribute in the surveillance of reservoirs of NNV in invertebrates of the unexplored western Mediterranean Sea. We report the detection of the RGNNV strain in two species of squid (Alloteuthis media and Abralia veranyi), and in one shrimp (Plesionika heterocarpus) collected in 2015 in the Alboran Sea. According to RNA2 sequences obtained from invertebrates and reported to date in the Mediterranean Sea, the strain RGNNV is predominant in this semi-enclosed sea. Our results suggest that RGNNV distribution is apparently independent of host species and ecosystem, and similar between invertebrates and fish species that feed on invertebrates, calling for an increase in surveillance of NNV reservoirs in the wild.European Association of Fish Pathologists. PathoVe