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

Abstract

The Nervous Necrosis Virus (NNV) is an aquatic pathogen responsible for a neurological disease affecting marine fish. Despite its almost worldwide distribution, global warming could favour NNV spreading towards new areas, highlighting the importance of conducting epidemiological surveys on both wild and farmed marine fish species. In this study we have assessed NNV prevalence in wild fish caught along the Galician Atlantic coast. A total of 1,277 fish were analysed by reverse transcription real‐time PCR (RT‐rtPCR), of which 1.72% tested positive for NNV, including two species in which the pathogen had not yet been reported. The reassortant RGNNV/SJNNV was detected in 55% of these individuals, while the remaining 45% harboured SJNNV type genome. Moreover, 4 reassortant strains were isolated from pilchard and mackerel which carry amino acid mutations at key sites related to NNV‐host interaction.

Comparative Analysis of Immune Gene Transcription in Sea Bream (Sparus aurata) Challenged with RGNNV or RGNNV/SJNNV Betanodaviruses

“…Transcriptional deregulation upon NNV infection in sea bream is not as evident as it has been described in other susceptible fish species, such as sea bass, Senegalese sole, zebrafish ( Danio rerio ) or Atlantic halibut ( Hippoglossus hippoglossus ), especially regarding the inflammatory response [ 36 , 37 , 38 ]. The “mild” inflammatory response detected in the present work has also been described in previous studies after sea bream inoculation with RGNNV, RGNNV/SJNNV and SJNNV/RGNNV [ 32 , 34 ] and can be related to the lack of typical symptoms of disease in this fish species, even when mortalities are recorded [ 12 , 39 ]. In fact, il-1β , which has not been induced by the viral infections in this study, has been proven to cause neurodegeneration in grouper brain [ 40 ], and tnf-α , which has been down-regulated by SaNNV infection ( Figure 2 ), although it has been suggested to protect neurons in NNV-infected grouper cells [ 40 ], has also been proven to induce neuropathology associated with viral infections in mammals [ 41 , 42 ].…”

“…In addition, reassortment between RGNNV and SJNNV segments has also been reported. Thus, SJNNV/RGNNV or RGNNV/SJNNV (RNA1/RNA2) betanodaviruses have been isolated from or detected in European sea bass ( Dicentrarchus labrax ), Mediterranean horse mackerel ( Trachurus mediterraneus ), common sole ( Solea solea ), Senegalese sole ( S. senegalensis ), hybrid groupers ( Epinephelus fuscoguttatus and E. lanceolatus ) and gilthead sea bream ( Sparus aurata ) [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ].…”