Detection of viral encephalopathy and retinopathy virus (VERV) in wild marine fish species of the South Tyrrhenian Sea (Central Mediterranean)

Abstract

Keywords: carrier, demersal fish, piscine nodavirus,RT-PCR, Tyrrhenian Sea.Betanodavirus infection has been reported to causediseases in a wide variety of marine fish species inaquaculture worldwide, and it is responsible ofsevere economic losses (Gagne et al. 2004; Walker& Winton 2010). Fish nodaviruses more com-monly cause disease and mortality of up to 100%in larval and juvenile stages, although adults canalso be affected (Munday & Nakai 1997; Gagneet al. 2004). Fish surviving infection can becomeasymptomatic carriers. Disease is characterized byabnormal swimming behaviours associated withvacuolar lesions in the nervous tissues containingviral particles. Clinical signs should be ascribed toone single disease, officially identified as viralencephalopathy and retinopathy (VER) also knownas viral nervous necrosis (VNN).The disease, present in the Mediterranean basin,affects farmed species such as European seabass,Dicentrarchus labrax L., and shi drum, Umbrinacirrosa L., but also wild species such as duskygrouper, Epinephelus marginatus (Lowe), and whitegrouper, Epinephelus aeneus (Geoffroy Saint-Hilaire) (Maltese & Bovo 2007). Nodavirus hasbeen identified in some wild apparently healthy fishbelonging to the following species: garfish, Belonebelone (L.), bogue, Boops boops (L.), thinlip greymullet, Liza ramada (Risso), whiting, Merlangiusmerlangus (L.), European hake, Merluccius merluc-cius (L.), flathead grey mullet, Mugil cephalus L.,red mullet, Mullus barbatus barbatus (L.), commonpandora, Pagellus erythrinus (L.), axillary seabream,Pagellus acarne (Risso), black goby, Gobius niger L.,European pilchard, Sardina pilchardus (Walbaum),gilthead seabream, Sparus aurata L., tub gurnard,Chelidonichthys lucerna (L.), and poor cod, Trisopte-rus minutus (L.), (Castric et al. 2001; Maltese et al.2005; Ciulli et al. 2006; Grodzki, Galletti & Ciulli2006).This study was aimed at determining the occur-rence of viral encephalopathy and retinopathy virus(VERV) in selected stocks of demersal fish species.Sampling: The study area is situated betweenCapo Suvero (the Calabrian coast) and Capo SanVito (the North-Western Sicilian coast) in theSouthernmost part of the Tyrrhenian Sea. Sam-plings were carried out during a summer trawl sur-vey and were performed with a commercial vesselequipped with an ad hoc designed net, with20 mm of stretched mesh size (Fiorentini et al.1999). A stratified random sampling method wasadopted (Relini 1998; Bertrand et al. 2002). Atotal of 23 hauls were carried out randomly allo-cated into five depth strata: A: 10–50 m(622 km