2 results
Environment
PROJECT NUMBER • 2010-061
PROJECT STATUS:
COMPLETED

National Guidelines to develop fishery harvest strategies

Harvest strategies offer an effective fisheries management tool to integrate the ecological, social and economic dimensions of fisheries management into a single framework for fisheries management decision making. As evidenced by their wide use internationally and throughout Australian fisheries...
ORGANISATION:
Department of Primary Industries and Regions South Australia (PIRSA)
TAGS
Workshop

Environmental risk factors that may contribute to vibrio outbreaks - A South Australian case study

Project number: 2021-097
Project Status:
Completed
Budget expenditure: $59,100.00
Principal Investigator: Stephen Pahl
Organisation: Department of Primary Industries and Regions South Australia (PIRSA)
Project start/end date: 30 Jun 2022 - 30 Oct 2022
:
SPECIES
Pacific Oyster

Need

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

1. To collate and record all available environmental conditions (pre- and post-harvest) associated with the recent vibrio outbreaks in South Australia
2. To review the environmental conditions which may have been risk factors contributing to the recent vibrio outbreaks in South Australia
3. To review available tools that could be used to identify and assess potential vibrio risk factors and any approaches for improved surveillance
4. Recommendations on data and information collection deficiencies related to the South Australian situation

Final report

ISBN: 978-1-876007-54-6
Authors: Stephen Pahl Navreet Malhi Hugo Bastos de Oliveira Alison Turnbull
Final Report • 2024-07-01 • 12.61 MB
2021-097-DLD.pdf

Summary

Vibrios are naturally occurring bacteria that are ubiquitous in fresh, estuarine and marine environments. Many Vibrio species are non-pathogenic, but some can cause disease in animals, and others are pathogenic to humans. People can contract vibriosis by consuming raw, undercooked or cross-contaminated seafood (predominantly oysters, crabs and shrimp) or exposing a wound to seawater. Bivalve molluscs, such as oysters, are a known vector for pathogenic bacteria as they are often consumed raw, and their filter feeding action concentrates bacteria within their tissues. Historically Vibrio parahaemolyticus has been rarely implicated in illnesses attributed to the consumption of Australian seafood. However, several recent outbreaks of gastroenteritis caused by V. parahaemolyticus in oysters have occurred in Australia.
 
An improved understanding of the environmental determinants was warranted to assist in future risk management considerations and food safety requirements. This report describes the results of the study undertaken which recorded the available and relevant environmental information and considered known risk factors relevant to V. parahaemolyticus that could be used for future investigations and to help underpin risk management considerations. 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 food safety issue.
 
Vibrios are part of the normal microbiota of many oysters and are ubiquitous in many other aquatic products. Vibrios multiply in oyster tissues at temperature-dependent rates before, during and after harvest. Across the two outbreaks, three sequence types (ST36, ST50 and ST417) were identified from clinical isolates and only one sequence type (ST417) was isolated from oysters as part of investigations following the second outbreak. The environmental conditions, notably sea surface temperature, oyster basket temperature and salinity, during the onset periods of the two Vibrio outbreaks (February 2021 and September 2021) were conducive to the growth of V. parahaemolyticus. However, there were no evident climatological anomalies in the collated data sets that help to substantiate why these Vibrio outbreaks occurred in South Australia at these times given that there had not been any significant changes in oyster production, harvest and post-harvest practices. 
 
This project has also highlighted several data gaps. Poor traceability through supply chain hampered traceback investigations and the identification of the unique harvest date, harvest location, and subsequent production, harvest and post-harvest conditions was limited. There is no information publicly available on the levels of detection of V. parahaemolyticus in the implicated oysters. The occurrence of these two and similar recent Vibrio outbreaks in Australia demonstrates that vibrios are a risk that requires 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 and molecular diagnostics. 
 
Recommendations
1. In-situ environmental monitoring is improved through use of loggers in more growing and harvest areas.
2. Further work needs to be undertaken within the supply chain to ensure that legislated responsibilities on labelling, traceability and control of co-mingling are adhered to.
3. Vibrio parahaemolyticus isolates should be collected during vibriosis events (clinical and oyster) and an Australian isolate collection curated and maintained.
4. A review and refresh of growers recall plans is necessary and growers should participate in simulation training of recall events to improve the practices supporting speedy recalls.
5. Open lines of communication between regulators and industry should be maintained to determine what type of data can be shared and when.
6. Authorities should implement timely closure of growing areas following multiple illnesses in line with ASQAP guidelines.
7. Food Safety Management plans should be reviewed and closely adhered to, especially if there are any future outbreaks.
8. Regulators should hold a post event review that includes industry and research representatives to strengthen working relationships and improve joint outcomes. 

Project products

Fact Sheet • 2025-01-15 • 388.29 KB
2021-097-summary.pdf

Summary

Vibrio parahaemolyticus is a bacteria commonly found in estuarine and marine environments and can cause foodborne illness through the consumption of raw or undercooked seafood.
Scientific information on key pathogenic Vibrio species, their ecology, environmental risk factors and potential mitigation strategies were reviewed for two Vibrio parahaemolyticus outbreaks that were traced back to Pacific oysters produced in South Australia. The first outbreak commenced in March 2021 and the second outbreak started in September 2021.
A range of tools and approaches are available which can be used to identify and assess potential Vibrio risk factors and improved surveillance. These include local and remote-sensing of the environment, microbiological sampling and molecular diagnostics.
 
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