Phylogenetic analysis of betanodavirus isolates from Australian finfish

Abstract

In Australia, disease caused by betanodavirus has been reported in an increasing number of cultured finfish since the first report of mortalities in 1990. Partial coat protein gene sequences from the T2 or T4 regions of 8 betanodaviruses from barramundi Lates calcarifer, sleepy cod Oxyeleotris lineolata, striped trumpeter Latris lineata, barramundi cod Cromileptes altivelis, Australian bass Macquaria novemaculata and gold-spotted rockcod Epinephelus coioides from several Australian states were determined. Analysis of the 606 bp nucleotide sequences of the T2 region of 4 isolates demonstrated the close relationship with isolates from the red-spotted grouper nervous necrosis virus (RGNNV) genotype and the Cluster Ia subtype. Comparison of a smaller 289 bp sequence from the T4 region identified 2 distinct groupings of the Australian isolates within the RGNNV genotype. Isolates from barramundi from the Northern Territory, barramundi, sleepy cod, barramundi cod and gold-spotted rockcod from Queensland, and striped trumpeter from Tasmania shared a 96.2 to 99.7% nucleotide identity with each other. These isolates were most similar to the RGNNV genotype Cluster Ia. Isolates from Australian bass from New South Wales and from barramundi from South Australia shared a 98.6% sequence identity with each other. However, these isolates only shared an 85.8 to 87.9% identity with the other Australian isolates and representative RGNNV isolates. The closest nucleotide identity to sequences reported in the literature for the New South Wales and South Australian isolates was to an Australian barramundi isolate (Ba94Aus) from 1994. These 2 Australian isolates formed a new subtype within the RGNNV genotype, which is designated as Cluster Ic. KEY WORDS: Betanodavirus · Phylogeny · Nervous necrosis virus · Coat protein · Nodavirus · Molecular detection Resale or republication not permitted without written consent of the publisherDis Aquat Org 87: [151][152][153][154][155][156][157][158][159][160] 2009 like viral particles were first reported to be associated with degenerative areas of the brain and retina of larvae which had exhibited abnormal swimming behaviour (Glazebrook et al. 1990, Munday et al. 1992. The close antigenic relationship of the picorna-like virus in diseased barramundi to the betanodavirus of striped jack nervous necrosis virus (SJNNV) was reported after specific fluorescence was observed in barramundi tissue using anti-SJNNV rabbit serum in an indirect fluorescence antibody test (Munday et al. 1994). Amplification and sequencing of the T4 region of the coat protein gene of an isolate from barramundi from Australia (Ba94Aus) confirmed betanodavirus as the causative agent (Nishizawa et al. 1997). Virions are small (25 to 30 nm), non-enveloped, icosahedral in shape, and contain single-stranded, bipartite positive sense RNA. The larger RNA segment (RNA1, 3.1 kb) encodes a nonstructural protein of ~110 kDa, while the smaller RNA segment (RNA2, 1.4 kb) encodes the 42 kDa coat protein (Mori et al. 1992, Murphy et...

Viruses of Fish: An Overview of Significant Pathogens

“…The virus infects a large range of host species—at least 40 species of marine and freshwater fish world-wide [30]—and the known host range continues to expand as new species of fish are used for aquaculture [38,39]. Of further interest is the potential of wild fish to become sub-clinical carriers as virus-contaminated water spreads from aquaculture enterprises into the marine environment particularly for those countries with large mariculture industries [40].…”

“…RNA1 encodes a non-structural protein and RNA2 encodes the coat protein [35,42,43]. Based on the coat protein gene sequence, betanodaviruses have been classified into a number of genotypes; the number of genotypes has increased from the initially proposed four [44] to at least five genotypes [45,46], and several sub-genotypes [39], which appear to be restricted to geographical locations relating to water temperatures [47]. …”

Host, agent and environment interactions affecting Nervous necrosis virus infection in Australian bass Macquaria novemaculeata

“…The isolate was obtained by subculture at low passage from 2 ml of SSN−1 cell culture supernatant (CCSN) containing the isolate described as T451722 GenBank accession no. (Moody et al., ).The isolate NNV_Mn06 was obtained from Australian bass with subclinical infection: a MnNNV_12/06 (GenBank accession nos. and ) (Hick, ).…”

Aquatic viruses induce host cell death pathways and its application

“…On the basis of the coat protein gene sequence, betanodaviruses have been classified into a number of genotypes. The number of genotypes has increased from the initially proposed four (Nishizawa et al, 1997) to at least five genotypes (Gagné et al, 2004;Johansen et al, 2004) and several sub-genotypes (Moody et al, 2009), which appear to be restricted to geographical locations relating to water temperatures ).…”

“…The disease is featured by necrosis of neural cells of the brain, retina and spinal cord and can cause up to 95% mass mortality in larval and juvenile fishes and significant losses in older fish. The virus infects a large range of host species -at least 40 species of marine and freshwater fish worldwide (Munday et al, 2002) -and the known host range continues to expand as new species of fish are used for aquaculture (Furusawa et al, 2007;Moody et al, 2009). Viral nervous necrosis has a wide geographical distribution that includes South and East Asia, Oceania, Mediterranean Europe and Tunisia, the UK, Norway and North America.…”