When a bacteria outbreak was traced back to Coffin Bay oysters in 2021, research was needed to understand the cause and help prevent future outbreaks.
'2021-097 Environmental risk factors that may contribute to vibrio outbreaks' is a South Australian case study supported by funding from the FRDC on behalf of the Australian Government.
Project background
Vibrio parahaemolyticus is a bacteria found in estuarine and marine environments and can cause illness through eating raw or undercooked seafood. Vibrio was rarely implicated in illnesses from Australian seafood, but there were outbreaks of gastroenteritis in February and September of 2021.
The outbreaks were traced back to Pacific oysters from South Australia, resulting in a closure of involved oyster bays and a recall of Coffin Bay oysters. These were the largest Vibriosis outbreaks on record for an Australian product and resulted in substantial costs for industry.
Objectives
Vibrio is an increasing risk to oyster farms in Australia, yet little was known about the cause. This project included investigating Vibrio's environmental factors and other research to help with future risk management and food safety requirements.
- Collate and record all available environmental conditions (pre- and post-harvest) associated with the 2021-2022 Vibrio outbreaks related to oysters produced in South Australia.
- Review the environmental conditions which may have been risk factors contributing to the 2021-2022 outbreaks related to South Australian oysters.
- Review available tools that could be used to identify and assess potential Vibrio risk factors and any approaches for improved surveillance.
- Provide recommendations on data and information collection deficiencies related to the South Australian situation
Research approach
SARDI's study included a review of scientific information on key pathogenic Vibrio species, their ecology, environmental risk factors, and mitigation strategies.
We collated available environmental data surrounding the time and location of the outbreaks. This included sea-surface temperatures, salinity, phytoplankton and chlorophyll-a, and weather observations from the Bureau of Meteorology and satellite data.
We analysed the data for any anomalies that may have contributed to the outbreaks. We also reviewed the available harvest data and supply chain information related to the South Australian situation.
We researched national and international jurisdictions for any approaches to improved surveillance or available tools to identify and assess potential Vibrio risk factors, then reviewed what we found.
Outcomes
Our research showed that environmental conditions—sea surface temperature, oyster basket temperature and salinity—during the onset periods of the two Vibrio outbreaks in 2021 were conducive to its growth.
However, there were no evident climatological anomalies in the collated data sets that help to substantiate why these Vibrio outbreaks occurred at these times, given that there had not been any significant changes in oyster production, harvest and post-harvest practices.
This project has highlighted several data gaps:
- Poor traceability through supply chain hampered traceback investigations.
- The identification of the unique harvest date, harvest location, and subsequent production, harvest and post-harvest conditions was limited.
- Lack of publicly available information on the levels of detection of Vibrio in the implicated oysters.
The 2 South Australian and similar recent Vibrio outbreaks in Australia shows that Vibrios are a risk that needs effective control mechanisms.
A range of tools and approaches are available that could be used to identify and assess potential risk factors and improved surveillance. These tools include:
- in-situ data collection
- remote sensing of the environment
- microbiological sampling
- molecular diagnostics.
Since the 2 Vibrio outbreaks in 2021, the control measures in South Australia have been strengthened to prevent or help limit the occurrence and severity of any future Vibrio outbreaks.
Project team
- Dr Stephen Pahl – Research Scientist, SARDI
- Ms Navreet Malhi – Research Officer, SARDI
- Dr Hugo Bastos de Oliveira – Research Scientist, SARDI
- Dr Alison Turnbull – Senior Research Fellow, Institute for Marine and Antarctic Studies, University of Tasmania
Project collaborators
- Institute for Marine and Antarctic Studies, University of Tasmania
- PIRSA Biosecurity – Food Safety Program
