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.