DEALING WITH SEAFOOD TOXINS - PRESENT APPROACHES AND FUTURE-OPTIONS

In most maritime countries, the seafood industry is an important source of revenue and accounts for a significant portion of the country's food supply. However, certain seafood, in particular shellfish, may become contaminated with naturally occurring toxins. The existence of shellfish toxins has been known for centuries and early attempts to deal with this threat led to the creation of folklore rituals and religious customs among tribal and ethnic groups. Eventually it was found that these toxins are produced by microbial organisms, usually phytoplankton, that occur naturally in the ocean. In Canada, as well as other countries with cold or temperate coastal waters, three groups of toxins are of particular importance and these are the paralytic shellfish poisoning (PSP) toxins, the diarrhetic shellfish poisoning (DSP) toxins and amnesic shellfish poisoning (ASP) toxin. Since it is virtually impossible to prevent the occurrence of these toxins, the approach in modern times has been to monitor seafood for the presence or absence of toxins using a standardized mouse bioassay. However, not all toxins can be detected effectively by this method and there is a trend in several countries to dispense with the mouse bioassay. Furthermore, there are differences between countries as to the preferred method of sampling and analysis and there is not agreement between all countries concerning tolerance levels of the various toxins in seafood. These difficulties, the occurrence of new toxins, and the rapid expansion of the shellfish aquaculture industry have put considerable pressure upon the scientific community to develop new methods of coping with these toxins, including more sensitive chemical or biochemical assays that are rapid and inexpensive. The possibilities and options for coping with these ubiquitous toxins are presented and discussed.