Algal Toxins in Shellfish

Knowledge of the existence of algal toxins in shellfish at certain times of the year has existed in certain cultures for centuries. Nowadays, shellfish sold commercially are tested, and the Norwegian Food Safety Authority provides advice on areas to avoid so as to prevent poisoning episodes.

What is an algal toxin and how do shellfish become toxic?

Shellfish, such as blue mussels, scallops and oysters, live by filtering plankton. Certain algae can produce or contain toxins. Shellfish can take up and concentrate the toxins during blooms of such algae. Marine algal toxins can occur in shellfish in all seasons, and the shellfish show no apparent ill effects from large amounts of toxin. The algal toxins do not affect the taste of the shellfish, and people therefore have no possibility of checking whether the shellfish are toxic on their own. The algal toxins are chemical compounds that are not destroyed by freezing or cooking.

What types of algal toxin do we have?

The algal toxins are divided into groups based on their effects

• Paralytic shellfish toxins PST) cause paralysis
• Diarrhetic shellfish toxins (DST) cause diarrhoea
• Amnesic shellfish poisoning (AST) cause amnesia

In addition, there are three groups of compounds called azaspiracids, pectenotoxins, and yessotoxins.

What methods do we have for detecting algal toxins in shellfish?

All shellfish that are sold commercially must be tested for the presence of algal toxins, and internationally it is only the so-called mouse test that is recognised for determining whether shellfish don’t contain high concentrations of PST and DST.

Depending on which toxin is being tested, different types of extracts are made of the shellfish meat are injected into the stomach cavity of mice. To limit the use of mice, and to obtain more information about which toxins are present, a range of chemical and immunological methods for analysis of algal toxins have been developed in recent years.

It is hoped that, within a relatively short time, sufficiently good chemical and immunological methods will be developed that can replace the mouse test. Chemical methods for determining algal toxins involve HPLC or LC-MS analysis. For some of the toxins there are also ELISA methods.

Regulation

Norway follows the EU’s regulatory framework for control of algal toxins in shellfish. The EU’s regulations are presented in: “Development of cost-effective tools for risk management and traceability systems for marine biotoxins in seafood”.

What is the National Veterinary Institute doing about algal toxins?

The National Veterinary Institute (NVI) has for many years worked with the problems associated with biotoxins such as mycotoxins and plant toxins and their occurrence in foodstuffs. Since 2000, the National Veterinary Institute has also been researching algal toxins in shellfish.

NVI is a partner in a large EU-financed research project, BIOTOX, which began at the start of 2004 and continued until early 2007. The project’s full title is: “Development of cost-effective tools for risk management and traceability systems for marine biotoxins in seafood.”. The project has 12 collaborating partners in 6 European countries.

The National Veterinary Institute’s activity is concentrated around three themes:

• Development of new methodologies for detection of algal toxins
• Identification of new algal toxins
• Depuration of algal toxins from shellfish.

Contact at the National Veterinary Institute

Chris. O Miles, researcher, Section for Chemistry
Telephone: +47 23 21 62 32
E-mail: chris.miles@vetinst.no

Thomas Rundberget, forsker, seksjon for kjemi
Telefon: 23 21 62 31
E-post: thomas.rundberget@vetinst.no

Ingunn Samdal, forsker, seksjon for kjemi
Telefon: 23 21 62 26
E-post: ingunn.samdal@vetinst.no

Morten Sandvik, forsker, seksjon for toksikologi
Telefon: 23 21 62 12
E-post: morten.sandvik@vetinst.no