Viral Encephalopathy and Retinopathy in groupers (Epinephelus spp.) in southern Italy: a threat for wild endangered species?

In late summer - early winter 2011 (September-December), significant mortalities affecting wild Dusky grouper (Epinephelus marginatus), Golden grouper (Epinephelus costae) and European sea bass (Dicentrarchus labrax) were reported in the municipality of Santa Maria di Leuca (Northern Ionian Sea, Italy). The affected fish showed an abnormal swimming behavior and swollen abdomens. During this epizootic, five moribund fish showing clear neurological signs were captured and underwent laboratory investigations. Analytical results confirmed the diagnosis of VER in all the specimens. Genetic characterization classified all betanodavirus isolates as belonging to the RGNNV genotype, revealing a close genetic relationship with viral sequences obtained from diseased farmed fish reared in the same area in previous years.The close relationship of the viral sequences between the isolates collected in wild affected fish and those isolated during clinical disease outbreaks in farmed fish in the same area in previous years suggests a persistent circulation of betanodaviruses and transmission between wild and farmed stocks. Further investigations are necessary to assess the risk of viral transmission between wild and farmed fish populations, particularly in marine protected areas where endangered species are present.Viral Encephalopathy and Retinopathy (VER) is a viral infectious disease affecting more than 50 marine fish species worldwide and it is considered one of the most important threats for mariculture in the Mediterranean.Fish affected by VER generally show clear clinical signs such as anorexia, skin darkening, blindness and abnormal swimming behaviour. Typical histological lesions include cellular vacuolation, necrosis and neuronal degeneration in the central nervous system (CNS).The aetiological agent of VER is comprised in the family Nodaviridae, genus Betanodavirus, and it is an icosahedral, non-enveloped viral particle of about 25？nm in diameter, with a genome made of tw