Key result
Australasian OsHV-1 isolates form a distinct genomic clade separate from European and Asian lineages.
Why the study?
OsHV-1 causes mass Pacific oyster mortality events worldwide and presents a substantial threat to global aquaculture, with variants linked to mortality events in Australia since 2010.
Whole-genome sequencing of OsHV-1 reveals a distinct Australasian clade, highlighting the need for whole-genome approaches over single-gene typing to understand viral evolution.
Supports region-specific OsHV-1 surveillance in Australasian oyster aquaculture; leaves open functional impacts of identified mutations.
Ostreid herpesvirus 1 (OsHV-1) is a major pathogen of Pacific oysters (Magallana gigas), linked to mass mortality events worldwide and presents a substantial threat to global aquaculture. Since 2010, mortality events have been occurring in Pacific oysters within Australia with the cause being an OsHV-1 microvariant highly similar to OsHV-1 μVar first detected in France, 2008. In this study, fifteen OsHV-1 whole genomes were assembled from Australian and New Zealand mortality events, including twelve newly sequenced genomes and three assembled from public datasets. Whole-genome phylogenetic analyses indicate that Australian and New Zealand OsHV-1 isolates form a distinct clade, separate from European and East Asian genomes, and with moderate regional and temporal divergence across the past 14 years. Across the dataset, multiple biologically relevant mutations were observed in genes of known function, including DNA polymerase, ribonucleotide reductase subunits, and apoptosis-related proteins, though most mutations occurred in uncharacterised genes. These findings highlight the limitations of single-gene typing and support the need for whole-genome approaches in understanding OsHV-1 evolution. Critically, the lack of recent whole-genome data, particularly from East and Southeast Asia, restricts the ability to trace viral origins and detect novel variants, underscoring the need for expanded global OsHV-1 genomic surveillance.
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O'Dwyer et al. (2026) studied OsHV-1 infection in Pacific oysters (n=15). Whole genome sequencing vs. European and East Asian OsHV-1 genomes was evaluated on Phylogenetic clade formation. Whole-genome phylogenetic analyses indicate that Australian and New Zealand OsHV-1 isolates form a distinct clade, separate from European and East Asian genomes.
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