Viral encephalopathy and retinopathy outbreak in freshwater fish farmed in Italy

Abstract

Viral encephalopathy and retinopathy (VER), otherwise known as viral nervous necrosis (VNN), is a neuropathological condition affecting > 40 species of fish. Although VER affects mainly marine fish, the disease has also been detected in certain species reared in freshwater environments. There are relatively few reports concerning the disease in freshwater species, and there is not much information on clinical signs. Nevertheless, the most common clinical findings reported from affected freshwater species are consistent with the typical signs observed in marine species. In this paper we describe the main clinical signs and the laboratory results associated with the detection of a betanodavirus in hybrid striped bass × white bass (Morone saxatilis × Morone chrysops) and largemouth bass Micropterus salmoides, reared in a freshwater environment. We also detected the virus by realtime PCR and isolated it in cell culture from a batch of pike-perch Sander lucioperca farmed in the same system.

Vacuolating encephalopathy and retinopathy associated with a nodavirus-like agent: a probable cause of mass mortality of wild Golden grey mullet (Liza aurata) and Sharpnose grey mullet (Liza saliens) in Iranian waters of the Caspian Sea

“…To date, the disease has been reported in more than 50 fish species, mainly marine with the greatest impact being in striped jack, European sea bass (Dicentrarchus labrax), groupers, and flatfishes [4,5]. A few outbreaks have also been documented in freshwater farms [6,7]. Recently, the disease has been considered as the most serious viral threat affecting marine farmed species in the Mediterranean region, thus representing one of the bottlenecks for further development of the aquaculture industry [8].…”

Genetic Characterization of Viral Nervous Necrosis Infects Tilapia (Oreochromis sp.) in Indonesia

“…Betanodavirus isolated from Epinephelus taurine (taurine Epinephelus Nervous Necrosis Virus=ETNNV) has high homolouges with virus isolated from freshwater fish Poecili areticula (Guppy Nervous Necrosisvirus=GNNV) [20]. Virus isolated fromMicropterus salmoides has high homologous with RGNNV [22]. In this study, VNN infected tilapia has homologous with RGNNV.…”

“…Infected fish demonstrate erratic swimming patterns and the neurological abnormalities, including cellular necrosis andvacuolization in the retina and the system of central nervous [19]. Some studies suggest that the VNN was not only attack the sea waterfish species,but also attack the freshwater fish species like an ornamental fish, guppy, Poicelia reticulata [20], Acipenser sp [21], fish medaka (Oryzias latipes) [19], largemouth black bass Micropterus salmoides [22], and tilapia, Oreochromis niloticus (L.) [23] [24].The genetic characterization confirmed that VNN infecting freshwater fish species was belong to the RGNNV genotype [19][25] [24] and the SJNNV genotype [19].…”

Dynamic distribution and tissue tropism of nervous necrosis virus in juvenile pompano (Trachinotus ovatus) during early stages of infection

“…The clinical signs of fish with NNV infections are uncoordinated or erratic swimming behavior and loss of appetite (Kuo et al, 2011). More than 40 species of fish from all continents, with the exception of Africa, that belong to the orders Anguilliformes, Perciformes, Pleuronectiformes, Tetraodontiformes, and Gadiformes are susceptible to NNV (Bovo et al, 2011). Epizootic NNV in marine aquaculture has been reported in several Asian countries, particularly China and Japan, and often leads to rapid mortality generally during early fry and fingerling stages (Furusawa et al, 2006;Liu et al, 2012).…”