Genetic analysis of aquabirnaviruses isolated from wild fish reveals occurrence of natural reassortment of infectious pancreatic necrosis virus

Abstract

In this study, we report the sequencing of the whole genome [including the 5' and 3' non-coding regions (NCR) of both segments A and B] of seven birnavirus strains isolated from wild fish from the Flemish Cap (FC) fishery at Newfoundland, Canada. From analysis and comparison of the sequences, most of the FC isolates clustered with the North American reference strains West Buxton (WB), Dry Mill and Jasper. One strain was included in the same genotype as the European strain Ab. In addition, at least in one case cohabitation of both type strains in an individual fish was demonstrated. These results clearly suggest the acquisition of the viruses from two different sources. The prevalence of the American type is easily explained by the close proximity of this fishing bank to the American coast whereas, although surprising, the presence of the European type strain could be because of migration of fish from European waters. In one strain, segment A and B sequences were typed differently (WB and Ab, respectively). These findings indicate natural reassortment between two strains of aquabirnaviruses in a host.

Isolation and Molecular Characterization of a Novel Infectious Pancreatic Necrosis Virus Strain in Returning Atlantic Salmon Salmo salar from the Connecticut River, USA

“…The polyprotein pVP2-NS (VP4)-VP3 and VP5 phylogenetic trees positioned Genogroup 4 (the Canada genogroup) more closely to the European, Asian, and Canadian Genogroups 5, 2, and 3. This observation coincides with previous phylogenetic work for Genogroup 4 using the whole polyprotein or a combination of genes VP2 and VP4 (Cutrín et al 2004;Zhang and Suzuki 2004;Nishizawa et al 2005;Romero-Brey et al 2009). The polyprotein and VP5 phylogenetic trees presented similar branching orders and grouping of the seven genogroups.…”

A combined RT-PCR and dot-blot hybridization method reveals the coexistence of SJNNV and RGNNV betanodavirus genotypes in wild meagre (Argyrosomus regius)

“…This is the first study showing the coexistence of both nodavirus genotypes in a single wild fish, which may lead to the re‐assortment of genomic segments. Although to demonstrate the presence of re‐assortants was not the aim of the present work, recent studies have reported the isolation of re‐assortant aquabirnavirus from wild fish (Romero‐Brey et al. 2009) and re‐assortant nodaviruses from farmed diseased fish (Toffolo et al.…”

Host range, host specificity and hypothesized host shift events among viruses of lower vertebrates

“…In addition, recently a molecular phenomenon was discovered among aquabirnaviruses, which could contributes to adaptation and replication in new hosts: natural reassortment. Thus, Romero-Brey et al [143] in an analysis of IPNV-like strains isolated from different species of wild fish captured in the Flemish Cap, Newfoundland [145] confirmed the presence of natural reassortants of the same type in a larger proportion of the population than in the Flemish Cap. The lack of information about segment B of most aquabirnavirus isolates reported in the literature means it is not known if reassortment is a common phenomenon in nature.…”