Monitoring for food safety in the shellfish industry
Global bivalve production has significantly grown over the past decades, with approximately 90% of the produce coming from aquaculture. In this context, the occurrence of harmful algal blooms (HABs) represents a significant and ongoing issue for the shellfish industry (especially of the filter-feeders), as some species of microalgae naturally produce marine biotoxins that can prevail in the water column and enter the food web, causing sicknesses and/or death of higher trophic organisms that consume them, including humans.
Currently, morphotype-based identification methods such as microscopy, are traditionally the standard monitoring tool to assess and manage regional ecosystems for the potential of HABs. However, it can be difficult to identify very small species, species that are misshapen due to the use of cell-fixing agents, and cryptic species. This is the case with some species of the former Alexandrium tamarense species complex, which are highly cryptic. Similarly, for many species within the diatom genus Pseudo-nitzschia, it is difficult to distinguish to species level without confirmatory molecular analyses. Other disadvantages of the current methods include difficulties with the logistics, such as transportation and cold-chain requirements, and the need of specialized laboratories, expensive reagents and equipment, and often time-consuming processing of the samples. Molecular genetic techniques that can be implemented in an aquaculture setting as rapid management tools, such as a multiplex qPCR assays to detect multiple HAB species in one assay, have the potential to be a feasible method for routine monitoring for seafood safety, giving comparable results to those of microscopy-based methods for analysing HAB abundance and distribution.
The aim of the present project is to develop and test a multiplex qPCR assay that can simultaneously detect Dinophysis species that produce Diarrhetic Shellfish Toxins (DST), a gene involved in Paralytic Shellfish Toxins (PST) biosynthesis (sxtA), and certain clade of Pseudo-nitzschia species that produce Amnesic Shellfish Toxins (AST). To achieve this aim, specific primers and probes were designed for a novel qPCR assay for the detection of Dinophysis species. Later, specificity, sensitivity, and efficiency of this multiplex qPCR assay aiming three different targets (ASP, DSP, and PSP) was tested in laboratory conditions with satisfactory results. Following this assessment, further evaluation of this multiplex qPCR assay with environmental samples is needed. The final stage of this project will consist in comparing qPCR results with current monitoring methods such as microscopy and biotoxin testing of shellfish flesh to evaluate the feasibility of the use of both methods to better understand HABs development, and act as an early warning monitoring system for food safety.
The development of this novel multiplex qPCR assay has the potential to provide a rapid, portable, low cost, and potentially automatised tool that can be used on farm, with data made available on-site, to develop an early warning system for managing HABs with specific application to the aquaculture shellfish industry.
To assist with building capability and understanding in seafood food safety in Australia, SafeFish also have the capacity to offer two 4-week summer placement opportunities per year to assist with delivering components of the SafeFish work program. For more information, please contact the Secretariat for more information.