environmental risk factors that may contribute to vibrio outbreaks - a south australian case study
BUDGET EXPENDITURE: $59,100
PRINCIPLE INVESTIGATOR: Dr. Stephen Pahl
ORGANISATION: Department of Primary Industries & Regions SA (PIRSA)
PROJECT CODE: 2021-097
PROJECT STATUS: Completed
WHY WAS THE RESEARCH UNDERTAKEN?
Vibrio parahaemolyticus can live in sediments and waters year-round and generally proliferates in the water
column when water temperatures are greater than 14degC. V. parahaemolyticus are rarely isolated from
seawaters below 10degC, though some cold-tolerant strains have been isolated overseas. The concentration
of V. parahaemolyticus in the water column increases as the water temperature increases. Oysters naturally
accumulate and depurate V. parahaemolyticus through filter-feeding, but once oysters are no longer
underwater, depuration can no longer occur and V. parahaemolyticus levels increase quickly unless the
oysters are less than 10degC. Recent outbreaks in South Australia have been very unusual in that they have
occurred in winter-spring. Other environmental factors including salinity, chlorophyll and turbidity have also
been linked to vibrio prevalence, but relationships are inconsistent. Internationally, some growing areas have
established relationships between V. parahaemolyticus and other environmental parameters such as
suspended matter, chlorophyll a and dissolved organic carbon, although this varies between areas and is not
consistent.
Little is known around why outbreaks have begun occurring in Australia and Vibrios are an increasing risk to
commercially produced oysters in Australia. The prevalence of vibriosis is globally linked to the effects of
climate change, aging populations, dietary changes and improved detection methods. It is vital that all
available relevant environmental data associated with these recent outbreaks is recorded and made available
for future interrogations. The identification of data gaps and tools that could be used to identify and assess
potential vibrio risk factors may help guide where additional effort is required to assist future understanding of
this complex and emerging food safety issue in Australia. This project is important to help defend current
demand, consumer trust and safety in oysters.
OBJECTIVES:
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To collate and record all available environmental conditions (pre- and post-harvest) associated with the
recent vibrio outbreaks in South Australia. -
To review the environmental conditions which may have been risk factors contributing to the recent
vibrio outbreaks in South Australia. -
To review available tools that could be used to identify and assess potential vibrio risk factors and any
approaches for improved surveillance. -
Recommendations on data and information collection deficiencies related to the South Australian
situation.
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