Nodavirus infections in Israeli mariculture

Abstract

Viral encephalopathy and retinopathy (VER) infections were diagnosed in five fish species: Epinephelus aeneus, Dicentrarchus labrax, Sciaenops ocellatus, Lates calcarifer and Mugil cephalus cultured on both the Red Sea and Mediterranean coasts of Israel during 1998-2002. Spongiform vacuolation of nervous tissue was observed in histological sections of all examined species. With transmission electron microscopy, paracrystalline arrays and pieces of membrane-associated non-enveloped virions measuring approximately 30 nm in diameter were observed in the brain and retina of all species. At the molecular level, the nodavirus was detected by using a primer set that amplified the T4 region of the coat protein gene. When the same set of primers was used to search for VER in an additional fish species, Sparus aurata, it was found to produce non-specific amplicons, giving rise to false-positive results. This problem was overcome by using a different primer set (F1/VR3), designed on a highly conserved region of the virus gene, which amplified a fragment of 254 bp, and confirmed that S. aurata was nodavirus-free. This set was validated on all five species of infected fish, as well as clinically healthy fish. Comparison of the coat protein genes from the Israeli isolated sequences indicated that more than one viral strain was involved. No strict host-specificity was evident. Red Sea and Mediterranean isolated sequences grouped in distinct clusters, together with several foreign isolates from the Mediterranean area and the Far East, as phylogenetically close to the Epinephelus akaara RGNNV type.

Viral encephalopathy and retinopathy (VER) in Atlantic salmon Salmo salar after intraperitoneal challenge with a nodavirus from Atlantic halibut Hippoglossus hippoglossus

“…However, another report suggests low host-fish specificity, as a cold-water clade nodavirus was isolated from sea bass Dicentrarchus labrax during an outbreak of VER at low temperature (Thiery et al 2004). The same conclusion was reached by a study of nodavirus infections in Israeli mariculture (Ucko et al 2004). The low host-fish specificity view is also supported by our study of Atlantic salmon.…”

Isolation, characterization and sequence determination of Noda virus from sea bass (Dicentrarchus labraxL.) reared in freshwater and marine facilities in Greece

“…Since the above isolates have distinct genomes, the hypothesis that the virus has no species barrier, can be accepted. This was also confirmed by Ucko et al (2004) in Israel, where no host specificity was evident in the virus isolates.…”

“…Αυτό αποδείχθηκε, επίσης, από τους Ucko και συν. (Ucko et al, 2004) από απομονώσεις στο Ισραήλ, όπου δεν υπήρχε εμφανής εξειδίκευση σε ξενιστή. Μετάδοση της νόσου παρατη ρήθηκε, επίσης, σε τσιπούρες (Castri et al, 2001), που μπορεί να είναι ασυμπτωματικοι φορείς, καθώς και σε λαβράκια (Le Breton et al, 1996).…”

Nodaviruses in Wild Fish Population Collected Around Aquaculture Cage Sites from Coastal Areas of Tunisia

“…The evolutionary distances were computed using the Kimura 2-parameter method [26] and are in the units of the number of base substitutions per site [27][28][29][30]. GenBank accession numbers and references for nucleotide sequences are as follow: EU826138.1 [31], EF617326 [32], NC_013461 [33], KF386164 [34], KY354698.1 [35], GU826692.1 [36], HE796793.1 [37], KY354694.1 [35], HE796789.1 [37], HE796797.1 [37], HE796788.1 [37], HE796791.1 [37], HE796790.1 [37], HE796785.1 [37], HE796798.1 [37], HE796799.1 [37], HE796794.1 [37], HE796786.1 [37], AJ698093.1 [38], AF318942.1 [39], AF499774.1 [40], HE796795.1 [37], HE796796.1 [37], HE796787.1 [37], HE796784 [37], KM588181.1 [41], KP455642.1 [42], AY284968.1 [43], HE796792.1 [37], JN190021.1 [44].…”