Domoic Acid and Amnesiac Shellfish Poisoning

ed tide, harmful algal occurred in 1987, when shell- blooms, shellfish poison- fish from Prince Edward Island, Ring, beach closures—you Canada, were consumed. In may have encountered these that outbreak, 3 people died issues when planning a clam- and more than 100 developed ming trip to the Oregon coast. a variety of toxin-induced What are these events that close symptoms. The most unusual— shellfish harvesting? and most serious—symptom was a loss of short-term

Beachdog.com memory; hence the initial Red Tide Call before you dig! Shellfish harvest hotline: designation of amnesiac shellfish Red tide occurs when appropri- 503-986-4728. poisoning. Unfortunately, for ate ocean conditions allow for many with short-term memory loss, the brain massive overgrowth of phytoplankton. These damage is permanent. The poison is not destroyed microscopic organisms undergo such rapid growth by cooking or freezing. that the phenomenon, called algal bloom, some- times will discolor the waters. Several of these Recent History of Amnesiac Shellfish Poisoning microorganisms produce toxins and store them in their cells, hence the term harmful algal blooms. Unsafe levels of domoic acid first appeared off the Shellfish such as clams, mussels, scallops, oysters, Washington and Oregon coasts in the fall of 1991, and cockles feed upon the phytoplankton, concen- when domoic acid was detected in razor clams. trating the poisons within their bodies. The poisons Razor clams accumulate domoic acid in the edible can sicken people who consume the shellfish. tissue (foot, siphon, and mantle), and the poison lingers in the tissue after the infestation in the Paralytic Shellfish Poisoning water is gone. In Dungeness crabs, domoic acid primarily accumulates in the gut (also known as Paralytic shellfish poisoning, caused by a substance the “butter”). called saxitoxin, has been around for many years and is routinely monitored along the west coast. The In 2001, along the beaches of Monterey Bay, culprit that produces this toxin is a microscopic California, dead and dying seabirds were observed. organism called a dinoflagellate, in the genus Many of the sick birds Alexandrium. This toxin can produce paralysis in displayed unusual humans, sometimes resulting in death. symptoms suggesting a neurological toxin. Domoic Acid Examination of the Domoic acid is a relatively new toxin and has contents of the dead

ashington

Rita Horner, University of University Rita Horner, recently appeared along the west coast of the birds’ stomachs re- W United States and Canada. Domoic acid is pro- vealed high levels of Magnified view of Pseudo- duced by the diatom Pseudo-nitzschia. The first domoic acid. nitzschia (elongated object running diagonally), which reported outbreak of domoic acid poisoning Continued produces domoic acid.

Shellfish harvest hotline: 503-986-4728 Furthermore, the birds had been eating anchovies When sea lions eat fish that contain domoic acid, from the bay. Examination of the anchovy gut the toxin gets into their bloodstream and damages contents showed that these fish had been consum- a part of their brain (the hippocampus). Sick sea ing a phytoplanktonic diatom called Pseudo- lions show a variety of symptoms: they may vomit, nitzschia australis. have seizures, and become depressed and comatose. Some of the animals died on the beaches. Most of Beginning in February 2002, more than 500 sick the affected sea lions were pregnant females. California sea lions came ashore in southern Because these moms were sick, they could not care California. This unusually high number of for their babies. strandings caught the attention of marine mammal scientists, who traced the condition to domoic Symptoms of Amnesiac Shellfish Poisoning acid. Symptoms of amnesiac shellfish poisoning include vomiting, nausea, diarrhea, and abdominal cramps Sea lions don’t eat the microscopic algae but fish within 24 hours of ingestion. In more severe cases, do, and sea lions eat the fish that eat the algae. neurological symptoms develop within 48 hours How can this be deadly? The toxin becomes and include headache, dizziness, confusion, disori- concentrated as it travels through the food chain. entation, and loss of short-term memory. This process is called bioaccumulation. In 2002, the domoic acid problem occurred almost exclusively What Should I Do if I Think Someone in common dolphins and sea lions. A large part of May Have Amnesiac Shellfish Poisoning? these animals’ daily diets is composed of filter- If symptoms are mild, call your health care provider feeding anchovies and sardines. Other animals and your local public health agency. If symptoms were spared because they eat different food items. are severe, call 911 or transport the affected person to the emergency room. There is no known anti- dote for ASP.

Shellfish harvest hotline: 503-986-4728

This publication was funded by the National Sea Grant Photo of clam diggers used with permission from beachdog.com. College Program of the U.S. Department of Commerce’s Magnified view of Pseudo-nitzschia used with permission from National Oceanic and Atmospheric Administration, the National Office for Marine Biotoxins and Harmful Algal under NOAA grant number NA16RG1039 (project Blooms, Woods Hole Oceanographic Institution, Woods Hole, number A/ESG-4), and by appropriations made by the MA 02543. Oregon State legislature. The views expressed herein do Text by Vicki Osis, marine education specialist, Extension Sea not necessarily reflect the views of any of those Grant, Oregon State University. organizations. © 2003 by Oregon State University. This publication may be photocopied or reprinted in its entirety for noncommercial purposes.

ORESU-G-03-005