Unhealthy oysters were observed after a plume of discoloured water was seen in the area following rainfall. Initial testing did not indicate presence of an infectious agent. A second submission (about one week after the first) indicated acute ulcerative changes indicative of an infectious agent.
The New South Wales Department of Industry and Investment identified the presence of ostreid herpesvirus-1 µ variant (OsHV-1 µ var) by PCR testing, subsequently this was confirmed by the Australian Animal Health Laboratory using conventional PCR. Virus particles could not be detected by transmission electron microscopy conducted on tissues from PCR positive samples.
The die off has also been observed in wild Pacific oysters in the nearby area. Mortalities have not been observed in other mollusc species, including adjacent Sydney rock oysters (Saccostrea glomerata). Oyster leases in other locations within Botany Bay have not been affected, and are under surveillance.
Mortality in Pacific oysters has been 100 per cent for spat (2.2mm), 95 per cent for market sized stock.
The New South Wales Food Authority advises there is no evidence to suggest any food safety issues with infected oysters.
The estuary is formally closed to all shellfish and associated equipment movements excepting movement of product to market. No Pacific oysters are available for market.
Surveillance outside and within containment and/or buffer zone including testing of source stock is being planned.
This virus has now spread throughout Europe to New Zealand and Australia.
Oyster Herpes Virus Hits Australia
AUSTRALIA - The New South Wales Department of Industry and Investment is investigating a syndrome of mortality in Pacific oysters (Crassostrea gigas), detected on oyster leases in Woolooware Bay, Botany Bay, New South Wales (South East Australia).
