A NSW Government website

Pacific Oyster Mortality Syndrome

Pacific Oyster Mortality Syndrome (POMS) is a disease of Pacific Oysters (Crassostrea gigas; also known by Magallana gigas). POMS affects Pacific Oysters and does not affect the Sydney Rock Oyster (Saccostrea glomerata) or the Flat Oyster (Ostrea angasi).

POMS does not have any impacts on human health and NSW Food Authority advises that all seafood in the marketplace remains safe to eat.

Reporting of suspected POMS mortalities

POMS is a notifiable disease and if suspected, must be reported to NSW DPI. Oyster growers are required to report unexplained mortality as per aquaculture permit conditions. Collect as much information as possible, including photographs of the mortality, an estimate of how much mortality is occurring, when the mortality was first seen, the waterway, nearest town, and any other identifying features.

To make a report, complete one of the following:

How does POMS affect oysters?

Pacific Oysters affected by POMS experience rapid and mass mortality. Mortality of up to 100% can be experienced in cultivated oysters within days of infection. The highest mortalities (between 60%-100%) occur in juvenile oysters (3-6 months in age), however all life stages have been recorded as susceptible.

Where does POMS occur?

The first reported POMS mortality outbreak was in France in 2008. Since then, POMS has been detected in the United Kingdom, Ireland, the Netherlands, Spain, Italy, Asia, New Zealand and Australia.

POMS was first confirmed in Australia in NSW in November 2010. In January 2016, oyster mortalities confirmed to be caused by POMS occurred in Tasmania. In February 2018, POMS was confirmed in the Port River of South Australia.

In NSW, POMS has been confirmed in three Pacific Oyster producing estuary systems, Botany Bay/Georges River, Hawkesbury River and Brisbane Water. POMS has also been confirmed in wild Pacific Oysters in Sydney Harbour/Paramatta River, where oyster farming does not occur. It is not known how POMS first arrived in NSW.

EstuaryOSHV1 first detected
Botany Bay/Georges RiverNovember 2010
Sydney Harbour/Paramatta RiverJanuary 2011
Hawkesbury River (including Patonga Creek)January 2013
Brisbane WaterFebruary 2013

Immediate reporting of these mortalities resulted in rapid action by NSW DPI to investigate the cause and implement controls on the movement of oysters and oyster cultivation equipment from these areas to help prevent further spread of the disease.

What drives disease outbreaks?

POMS is a seasonal disease where clinical infection and mortality is most prevalent during the summer months. Once POMS is introduced to an estuary system impacts generally persist on an annual basis. In NSW, mortality occurs once water temperatures reach and sustain a minimum 21°C, although in Europe, a lower threshold temperature of 16°C has been reported. Studies in Europe found that POMS was detectable in oysters after mortalities ceased, which indicates that surviving oysters can act as carriers of the disease. At this stage, there is still a lot to be learned about the POMS lifecycle.

NSW DPI can investigate the mortality event. If required, NSW DPI can coordinate the submission of samples to the State Veterinary Diagnostic Laboratory at NSW DPI Elizabeth Macarthur Agricultural Institute to exclude or confirm disease.

What you can do to help

NSW DPI encourages anybody that observes suspected aquatic disease events to report them so they can be investigated. Fish Care Volunteers, recreational fishers and community groups can assist by reporting any observed mortality outbreaks in wild Pacific Oyster populations.

Cleaning boats, trailers, kayaks fishing gear and other equipment before moving to another waterway can greatly help reduce the spread of aquatic diseases and pests. Read how via this aquatic hygiene factsheet and Make 'clean' part of your routine.

The oyster aquaculture industry has an important role to play in managing POMS in NSW estuaries. Movement controls are currently in place to manage biosecurity risks posed by shipping cultivated oysters and cultivation equipment between NSW estuaries. See Biosecurity Requirements to read more and ensure you understand your obligations as a NSW aquaculture permit holder.

Resources and further reading

General information:

Information for the Aquaculture Industry

Information for restaurants:

Published research

  • Petton B, Destoumieux-Garzon D, Pernet F, Toulza E, de Lorgeril J, Degremount L, Mitta G (2021) The Pacific Oyster Mortality Syndrome, a polymicrobial and multifactorial disease: state of knowledge and future directions. Frontiers in Immunology 12:630343
  • King WL, Siboni N, Williams NLR, Kahlke T, Nguyen KV, Jenkins C, Dove M, O’Connor W, Seymour JR, Labbate M (2019) Variability in the composition of Pacific Oyster microbes across oyster families exhibiting different levels of susceptibility to OsHV-1 µvar disease. Frontiers in Miccrobiology 10:473
  • Whittington RJ, Liu O, Hick PM, Dhand N, Rubio A (2019) Long-term temporal and spatial patterns of Ostreid herpesvirus 1 (OsHV-1) infection and mortality in sentinel Pacific oyster spat (Crassostrea gigas) inform farm management. Aquaculture 513:734395
  • de Kantzow M, Hick P, Becker JA, Whittington RJ (2016) Effect of water temperature on mortality of Pacific Oysters Crassostrea gigas associated with microvariant ostreid herpesvirus 1 (OsHV-1 µVar). Aquaculture Environment Interactions 8:419-428
  • Hick P, Evans O, Looi R, English C, Whittington RJ (2016) Stability of Ostreid herpesvirus-1 (OsHV-1) and assessment of disinfection of seawater and oyster tissues using a bioassay. Aquaculture 450:412-421
  • Paul-Pont I, Evans O, Dhand NK, Rubio A, Coad P, Whittington RJ (2014) Descriptive epidemiology of mass mortality due to Ostreid herpesvirus-1 (OsHV-1) in commercially farmed Pacific oysters (Crassostrea gigas) in the Hawkesbury River estuary, Australia. Aquaculture 422-423:146-159
  • Jenkins C, Hick P, Gabor M, Spiers Z, Fell S, Gu X, Read A, Go J, Dove M, O’Connor W, Kirkland P, Frances J (2013) Identification and characterisation of an ostreid herpesvirus-1 microvariant (OsHV-1 µ-var) in Crassostrea gigas (Pacific oysters) in Australia. Diseases of Aquatic Organisms 105: 109-126