Spatial and seasonal variability of human and fish viruses in mussels inside and offshore of Ravenna’s harbour (Adriatic Sea, Italy)

Abstract

Aims This study aims to investigate the presence and spatial‐seasonal variability of human and fish viruses in coastal marine systems using Ravenna’s harbour area (Adriatic Sea, Italy) as a model. Methods and Results Human viruses (noroviruses and hepatitis A virus) and one of the most threatening finfish pathogens, the nervous necrosis virus (NNV), were investigated in mussels living inside and offshore Ravenna’s harbour. Thirty‐three and 36·7% of tested mussel samples resulted contaminated by human and fish viruses respectively. A different spatial‐seasonal distribution was observed. Human viruses were detected mainly in inner port sites during colder months, while NNV was detected in both inside and offshore of Ravenna’s harbour, mainly during warmer months. Conclusions The presence of human viruses in the inner port close to the city centre could be attributed to wastewaters carrying pathogens in the port environment and this arises public health concerns, however, the presence of these viruses limited to the canal port during the winter can greatly reduce the risk to human health. Regarding NNV, the accumulation and release of viable virus by mussels, could represent a viral source for susceptible finfish. These findings reflect the different epidemiological features of these infections and indicate the importance to choose the correct indicator to monitor viral contaminations. Significance and Impact of the Study The high frequency of viral contamination pointed out in the study stresses the imperative to monitor the viral presence in all coastal habitats where the high natural value meets several recreational and commercial activities such as the Ravenna’s harbour area. Particularly, this study could represent a novel starting point for the development of a more structured bio‐monitoring program, in order to ensure improved environmental management and safety of coastal areas.

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

“…To date, the SJNNV/RGNNV reassortant has been mainly identified in fish species from Italy or Greece [35,36]. Interestingly, the reassortant SJNNV/RGNNV has been recently detected in mussels collected in the Adriatic Sea [9]. The RGNNV/SJNNV reassortants exhibit a slightly modified SJNNV capsid protein [4], thus, we can assure that this reassortant was not detected in the present study.…”

“…Regarding the Mediterranean sea, RGNNV has been detected in bivalve mollusks in the coast of Italy [20], in the Adriatic Sea [21] and in Greece [22]. A recent study on bivalve mollusks in the Adriatic Sea reported apparent RGNNV/SJNNV reassortants, although RGNNV was the main strain detected [9]. As for other invertebrate species, NNV was also documented in Italy in naturally deceased specimens of cultured and wild octopus presenting skin lesions [23], in Greece in gastropod samples [22] and in specimens of the blue crab from the Levantine Sea [24].…”

“…The four recognized betanodavirus strains are discriminated according to sequence homology of RNA2 encoding the coat protein; SJNNV (Striped jack nervous necrosis virus), TPNVV (Tiger puffer nervous necrosis virus), BFNNV (Barfin flounder nervous necrosis virus), and RGNNV (Redspotted grouper nervous necrosis virus) [8]. Reassortment of RNA1 and RNA2 gene fragments of different strains results in reassortant strains, and an example is the RGNNV/SJNNV reassortant, currently a threat for the marine aquaculture industry in the Mediterranean [9].…”

“…After detecting the RGNNV strain in invertebrate species of the ALB, we compiled our data in Table 3 with other studies reporting NNV in shellfish species collected in the Mediterranean Sea [9,20,[22][23][24]. A total of eight invertebrate marine species have been documented to host RGNNV, and they are categorized in a broad range of taxonomic classes (Bivalvia, Gastropoda, Cephalopoda and Malacostraca).…”

“…All invertebrate animals reported as hosts of RGNNV are widely distributed in the Mediterranean Sea. In the case of bivalve mollusks, the RGNNV strain has been detected in mussels and clams that were collected in Sicily, in the Adriatic Sea and in the Aegean Sea [9,20,22]. For gastropod mollusks, the virus was detected in a single species, Stramonita haemastoma, collected in Greece [22].…”