Biology Reference
In-Depth Information
Diarrhetic Shellfi sh Poisoning (DSP)
Thousands of cases of gastrointestinal disorders caused by diarrhetic
shellfi sh poisoning (DSP) have been reported in Europe, Japan and Chile
(WHO, 1984). The causative dinofl agellates, which produce the toxins, are
within the genus
Dinophysis
and
Aurocentrum
. These dinofl agellates are
widespread which means that this illness could also occur in other parts
of the world. At least seven toxins have been identifi ed, including okadaic
acid. The onset of disease is within half an hour to a few hours following
consumption of shellfi sh that have been feeding on toxic algae. Symptoms
are gastrointestinal disorder (diarrhea, vomiting, abdominal pain) and
victims recover within 3-4 d. No fatalities have ever been observed.
Neurotoxic Shellfi sh Poisoning (NSP)
Neurotoxic shellfi sh poisoning (NSP) has been described in people
who consumed bivalves that have been exposed to “red tides” of the
dinofl agellate (
Ptychodiscus breve
). The disease has been limited to the Gulf
of Mexico and areas off the coast of Florida. Brevetoxins are highly lethal
to fi sh and red tides of this dinofl agellate are also associated with massive
fi sh kills. The symptoms of NSP resemble PSP except that paralysis does
not occur. NSP is seldom fatal.
Amnesic Shellfi sh Poisoning (ASP)
Amnesic shellfi sh poisoning (ASP) has only recently been identifi ed
(Todd, 1990, Addison and Stewart, 1989). The intoxication is due to domoic
acid, an amino acid produced by the diatom
Nitzschia pungens
. The fi rst
reported incidence of ASP occurred in the winter of 1987/88 in eastern
Canada, where over 150 people were affected and four deaths occurred
after consumption of cultured blue mussels. The symptoms of ASP vary
greatly from slight nausea and vomiting to loss of equilibrium and central
neural defi cits including confusion and memory loss. The short-term
memory loss seems to be permanent in surviving victims, thus the term
amnesic shellfi sh poisoning.
The control of marine biotoxins is diffi cult and disease cannot be entirely
prevented. The toxins are all of non-protein nature and extremely stable
(Gill et al., 1985). Thus cooking, smoking, drying, salting does not destroy
them, and from the appearance of fi sh or shellfi sh fl esh it is diffi cult to
identify whether it is toxic.
The major preventive measure is inspection and sampling from fi shing
areas and shellfi sh beds, and analysis for toxins. The mouse bioassay is
often used for this purpose and confi rmatory HPLC (High Performance
Liquid Chromatography) is done if death occurs after 15 min. If high
levels of toxin are found, commercial harvesting needs to be halted.
