Algal toxins

Algal toxins

Algal toxins can cause diarrhoea, vomit, tingling, paralysis and other effects in humans, mammals or fish. Algal toxins are produced by various algae and are found both in seawater and fresh water. The algal toxins can be retained in shellfish or contaminate drinking water. They have no taste or smell and are not eliminated by cooking or freezing.

A series of such marine algal toxins are known, and among them are okadaic acid and the dinophysistoxins, saxitoxins, brevetoxins, domoic acid, azaspiracids, pinnatoxins, yessotoxins, pectenotoxins and cyclic imines, and most of them are found all over the world.

On a worldwide basis, marine algal toxins are responsible for many incidents of human intoxications every year, some even resulting in death. In addition to their human health effects, algal toxins are responsible for extensive die-offs of fish and have been implicated in the episodic mortalities of marine mammals, birds, and other animals dependent on the marine food web.

The situation in Norway

The two most common marine algal toxins along the coast of Norway can cause diarrhoea, vomit, and stomach cramps or tingling in lips/mouth and short term paralysis. The poisonings symptoms have led to the names "diarrheic shellfish poisoning" (DSP) and "paralytic shellfish poisoning" (PSP). Most of the algal toxins have been found in Norwegian shellfish, but its only DSP and PSP that have been associated with food poisoning episodes in Norway.

The algae causing PSP are usually blooming late spring until early summer. The algae producing DSP, are usually blooming along the coast at the end of summer and in the autumn. At the last reported food poisoning episode in Norway, in summer 2002, more than 200 people got sick with typical DSP symptoms after eating brown crab meat. This was unusual, and is probably due to an unusually early algal bloom, resulting in toxic blue mussels and for the first time also the toxic brown crabs.

Shellfish intended for the commercial market are controlled for quality at harvest, with respect to algal toxins as well as to micro-organisms, heavy metals, organic environmental toxins, and presence of potential toxin producing algae in the sea, as part of a program initiated by the former Directorate of Fisheries.

To maintain a certain security for the public picking shellfish for consumption, the Norwegian Food Safety Authority give advise on shellfish at “Matportalen.no”, on “the blue mussel phone 820 33 333” or at “NRK Tekst-TV page 695”, based on analysed samples and algal counts at certain stations along the coast.