The first reported incident of amnesic shellfish poisoning (ASP) occurred in PEI in 1987 when the ingestion of blue mussels was linked to 19 hospitalizations and 4 deaths. The causative agent was domoic acid (DA), a heat resistant tricarboxylic imino acid responsible for the permanent and irreversible memory loss in affected individuals. DA is produced globally by certain marine algae and enters the food chain through filter-feeding bivalves. Although outbreaks of ASP are relatively infrequent in Canada, it is mainly due to the intensive sampling and shellfish toxin testing carried out by the Canadian Food Inspection Agency (CFIA). The major control measure is that monitored sites with >20 ug DA/g shellfish tissue are closed, leading to harvesting interruptions and negative economic consequences. Additionally, inability of growers and processors to meet contractual obligations can compromise future contracts, resulting in loss of market share.
Natural depuration of DA from shellfish is species- and environmentally-dependent. Although DA-degrading bacteria isolated from bivalve digestive tracts have been reported in the past by Stewart et al. (1998), to date no reports have been published on the practical use of these organisms. Given that screening methods for such bacteria have been published, we intend to optimize these processes by monitoring DA degradation kinetics in vitro and delivering "competent" cultures to living shellfish. Commercial application of this technology will have a dramatic impact on the industry, complementing our parallel developments on elimination of paralytic shellfish toxins.
The project involves the recovery of marine bacteria capable of destruction of amnesic shellfish toxin (AST) and then to apply the same probiotic delivery platform now being developed under an NSERC I2I grant. It is our intention to provide two different micro-encapsulated probiotic products: one to eliminate PSTs and one for the destruction of AST in cultured shellfish, the latter development being supported through the STAR Grant. Thus, the STAR project involves screening marine bacteria with the ability to degrade AST as a key carbon source in the screening media. Bacteria competent in AST degradation will be micro-encapsulated using the same delivery system developed for the PST project.
The project provides a multi-disciplinary approach and involves input from university, government and industry. Network investigators include a microbiologist (Garduno), a food scientist (Gill) and the aquaculture expertise of John Batt and his technical staff at the Dalhousie Aquatron facility. Collaborators will include a shellfish grower (Hancock), a commercial shellfish depuration facility (Innovative Fishery Products) as well as personnel from the CFIA (Shaw). Carrie Donovan, a Research Associate, is one of the applicant’s former graduate students having completed her M.Sc. thesis on bacterial destruction of PSTs.
