Isolation and Genetic Characterization of Betanodavirus from Wild Marine Fish from the Adriatic Sea

Betanodavirus infection is widespread in a broad spectrum of fish species worldwide. In Italy, it is responsible for outbreaks of Viral Encephalo-Retinopathy (VER) that cause mortality and economic losses mainly in European sea bass (Dicentrarchus labrax) farming. Betanodaviruses are classified in the Nodaviridae family and 4 official species are present in the genus: BFNNV, Barfin Flounder Nervous Necrosis Virus, RGNNV, Redspotted Grouper Nervous Necrosis Virus, SJNNV, Striped Jack Nervous Necrosis Virus and TPNNV, Tigger Puffer Nervous Necrosis Virus. Recent studies have showed that the infection is also widespread in wildlife (Gagne et al., 2004; Guercio et al., 2004), where there are generally no observed clinical manifestations. Interspecies transmission has been demonstrated and the presence of asymptomatic carriers in wildlife is strongly suspected. The risk of horizontal transmission between wildlife and farmed fish is particularly high in fattening farming of marine fish that is generally conducted in sea cages or in brackish ponds where there is high possibility of contact with natural environment. As there is no efficient control system available for this infection, knowledge regarding the extent of its spread is fundamental for direct prophylaxis and control of the disease. In this study we investigated the presence of Betanodavirus infection in wild fish population in Adriatic Sea and genetically characterised the strains isolated to compare them with strains isolated during outbreaks with mortality in farmed fish.