Domoic
Acid (ASP) in Shellfish
What
is domoic acid?
Domoic
acid is a naturally occurring toxin produced
by microscopic algae, specifically the diatom species Pseudo-nitzschia.
Shellfish and crab ingest this algae, where the toxin concentrates. Significant amounts of domoic acid can cause
Amnesic Shellfish Poisoning (ASP) in humans. ASP is transmitted by
eating contaminated molluscan shellfish and crab.
How
long has domoic acid been a problem?
In
the fall of 1991, domoic acid was detected in razor clams off the coast of
Washington. In that same year, DOH began
monitoring all major shellfish growing areas for domoic acid.
Is
domoic acid present in all seafood?
Unsafe levels of domoic acid have been detected in razor clams and
Dungeness crab in Washington coastal waters. Domoic acid has also
been found in mussels, clams, and
oysters in Puget Sound areas.
Razor clams accumulate domoic acid in the edible tissue (foot, siphon and
mantle) and are slow to rid themselves of the toxin. In Dungeness crab, domoic acid
primarily accumulates in the viscera
(also known as the gut or "butter").
Does
cooking the shellfish make it safe to eat?
No. The
toxin is not destroyed by cooking or freezing.
What
are the symptoms of ASP?
Symptoms include vomiting, nausea, diarrhea and abdominal cramps
within 24 hours of ingestion. In more severe cases, neurological symptoms
develop within 48 hours and include headache, dizziness, confusion,
disorientation, loss of short-term memory, motor weakness, seizures,
profuse respiratory secretions, cardiac arrhythmias, coma and possibly
death. Short term memory loss is permanent, thus the name Amnesic
Shellfish Poisoning.
What should I
do if I think someone may have ASP?
If symptoms are mild, call your health care provider and your local public
health agency. If symptoms are severe, call 911 or transport the
affected person to the emergency room. There
is no antidote for ASP.
How can I
protect myself from ASP?
Because there is no antidote for ASP, prevention is the best protection.
For all species, always check the State Department of Health Biotoxin
Closures at
www.doh.wa.gov/biotoxinmaps.htm or call the Biotoxin Hotline at
1-800-562-5632.
In addition
to checking the status of Biotoxin closures:
-
For razor clams: the Washington State Department of Fish & Wildlife periodically opens
recreational
razor
clam seasons (Fish & Wildlife website), and does so only after DOH testing shows domoic acid to
be at safe levels. Razor clam harvest is allowed only on days and in areas officially opened by Fish &
Wildlife.
-
For Dungeness crab: check
Fish and Wildlife crab harvest seasons and be sure to clean the crab thoroughly, removing all viscera.
Before
going to the beach always check the DOH website at
www.doh.wa.gov/biotoxinmaps.htm, call the Biotoxin Hotline at
1-800-562-5632, or call your local health department.
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