ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY MEMO
 Department of Agricultural Chemistry, Oregon State University   
                  Jeff Jenkins, Specialist

        SUBJECT: Domoic Acid in Oregon Seafood Harvest

"Domoic acid found in Oregon and Washington shellfish(1)." "Toxin
sinks crabbers' Christmas(2)." These headlines in Oregon
publications in November and December 1991 announced the
discovery of domoic acid in seafood harvested in Oregon. This
toxin, found in crabs and razor clams in Oregon, has both
economic and human health implications for Oregonians.

DOMOIC ACID DEFINED

While some things are known about domoic acid, there are still
many areas where much more research is needed. Domoic acid is a
naturally occurring excitatory neurotoxic amino acid that is
structurally related (an analog) to the much studied glutamic
acid(3). Glutamic acid is an abundant amino acid normally found
in humans. It transmits impulses from one cell to another along
the central nervous system and some of these impulses end up in
the hippocampus of the brain, the site of learning and memory. If
a chemical like domoic acid, which mimics glutamic acid, is
transported to the hippocampus, the normal impulse balance is
disturbed and an excitotoxic event will occur(4). The receptors
in the hippocampus send continuous impulses and can "burn out,"
resulting in brain lesions and permanent memory loss(5). It is
this disturbance that characterizes amnesic shellfish poisoning
(ASP), named for the neurological symptoms it produces.

OCCURRENCES OF DOMOIC ACID

The seaweed Chondria armata, C. baileyana, and Alsidium
corallinum all contain measurable quantities of domoic acid(6).
In Japan, extracts from Chondria armata have long been used as
worm medicine, and its insecticidal properties are well known(3).
Domoic acid is also present in some phytoplankton, such as the
diatoms Nitzschia pungens f. multiseries, N. psudodelicatissima,
and N. pseudoseriata (also called Pseudonitzchia australis)(7) It
is the P. australis that has been implicated in the detection of
domoic acid in Oregon(8).

One phytoplankton diatom that can produce domoic acid, N. pungens
f. multiseries, has been firmly identified on the east coasts of
North and South America, the west coast of North America, and in
Korea and Norway(9). Although the factors influencing the
production of domoic acid are not well understood, it is known
that domoic acid is produced only during the stationary phase or
non-dividing stage of this diatom. Specific light and nitrogen
conditions are essential for domoic acid production by the
diatom(7).

EARLY REPORTS

In November 1987 the first documented cases of domoic acid
causing human health effects were recorded on Prince Edward
Island, Canada, when 4 people died and 140 became ill from eating
contaminated mussels(10). The illness, ASP, was determined to
have been caused by a massive bloom of N. pungens f. multiseries,
an important food source for mussels. Similar blooms have
occurred since 1987, but monitoring by Canadian officials has
kept contaminated mussels from being harvested during such
blooms. Since domoic acid is not destroyed by cooking the
contaminated shellfish, avoidance is the key to prevention of
illness and deaths.

RECENT EVENTS

The deaths of sea birds in Monterey Bay, California in September
1991 led to the identification of domoic acid on the West
Coast(11). In Oregon, domoic acid was detected November 10, 1991
in razor clams harvested from the surf zone, and two days later
the season was closed to all shellfish harvesting. By November 21
the season was reopened for all shellfish except razor clams. All
beaches were reopened on December 3, with the exception of
Clatsop County, which contains large beds of razor clams. Crab
season was opened on December 3 but closed again on December 11
at the request of the industry when trace amounts of domoic acid
were found in crab meat. The season was reopened on December 22
with warnings from the Food and Drug Administration (FDA) that
consumers should not eat the crab viscera(11). The FDA has
proposed a regulatory limit of 20 ppm domoic acid in shellfish,
based on the Canadian limit, which is also 20 ppm(12).
Authorities continue to monitor Clatsop County where levels in
razor clams were above 20 ppm in May 1992. Levels in crab meat
were below 10 ppm in the meat and below 50 ppm in the viscera
when tested in spring 1992(8). Since crab viscera makes up about
45 % of the crab by weight, viscera could have domoic acid levels
as high as 44 ppm and the crab would still meet FDA standards. It
is estimated that if an individual consumed about half a pound of
material which had an excess of 20 ppm there could be a toxicity
problem. Populations which eat the viscera as food generally use
it as a condiment, rather than as an entire meal(13).

The National Marine Fisheries Service (NMFS) is coordinating the
sampling in Oregon in a cooperative effort with the Oregon
Department of Agriculture (ODA). The short term goal of sampling
is to give the seafood industry some advanced warning of the
presence of domoic acid. The long term goal is to learn more
about the causative agents(13).

TOXICITY

As with many other substances, the toxicity of domoic acid
depends on the route of exposure. In Japan domoic acid was tested
orally on humans at 0.5 mg/kg with no ill effects. It caused
gagging and vomiting when given orally to monkeys at doses of 5
and 10 mg/kg. Scientists estimate that, based on domoic acid
levels of 900 to 1200 ppm found in Canadian mussels, individuals
could consume as much as 5-6 mg/kg, enough to cause symptoms of
poisoning(3). When injected, domoic acid appears to be about ten
times more toxic to an animal than when it is ingested. Domoic
acid does not absorb well from the gastrointestinal tract, but
individuals with intestinal lesions or reduced renal function may
be at increased risk. Preliminary studies reveal no teratogenic
activity(3) and, within the limits of the test system employed,
it is not mutagenic(14). No information is available on chronic
low-level exposure or historical evidence of domoic acid health
effects(15).

DETECTION AND ANALYSIS

The domoic acid molecule (C5H21NO6) has been well defined(16).
When the structure is subjected to ultra violet (UV) irradiation,
three isomers are formed and have been identified. These isomers
do not bind as tightly to the neurological receptor as the parent
compound(17). Analysis of seafood samples is done by high
pressure liquid chromatography (HPLC) with the level of detection
at 1 ppm(18). Domoic acid is difficult to detect in blood or
urine by HPLC analysis. Therefore, feces that are collected
within 24 hours of exposure and frozen are the theoretical sample
of choice for the detection of domoic acid in humans. Serum and
urine analyzed by radio immunoassay (RIA) and enzyme-linked
immunosorbant assay (ELISA) have been investigated and these
methods show promise for low level detection; however, they are
not routinely available(19).

Pure domoic acid forms colorless crystal needles that are soluble
in both water and dilute mineral acids, as well as in alkali
hydroxide solutions. Domoic acid is minimally soluble in methanol
and ethanol and insoluble in petroleum ether and benzene(20).
Because of its solubility in water, there is reason to think that
low levels of domoic acid are present in sea water. However,
animals are probably at greater risk from contaminated food
sources, such as phytoplankton, than from sea water. In addition,
tests show that some shellfish purge themselves of domoic acid
when held several weeks in tanks of clean water(17). No data is
available for crab or razor clam purging.

ASP AND OTHER HEALTH RISKS

ASP is characterized by the onset of severe illness any time
after ingestion of contaminated shellfish, usually within 24
hours of ingestion. Patients can exhibit acutely developed
confusion, profound memory loss, and disorientation(10). Memory
loss was present in 26% of the ASP cases reported in Canada; some
individuals displayed clinical amnesia while others were able to
return to their original jobs. Intensive care hospitalization and
death were directly related to age(10), which leads to
speculation that the affected neurological receptor may be more
sensitive in old age than at any other time in life(21). Symptoms
exhibited by individuals were governed by the amount of mussels
eaten, the levels of domoic acid in the mussels, and the persons'
susceptibilities to absorption(22). There are many other
illnesses caused by seafood consumption. Three of these are as
follows: paralytic shellfish poisoning (associated with "red
tides"); ciguatera, the most common fish borne illness worldwide;
and scombroid, an illness often mistaken for a fish allergy(23).
Oregon Division of Health records indicate two possible cases of
ASP in Oregon(24).

In Canada, several criteria were used in a case definition of
possible ASP. The onset of the first gastrointestinal symptoms
was from 15 minutes to 38 hours, with a median of 6 hours. The
onset of neurological symptoms was from 2 hours to 58 hours, with
a median of 16 hours . The illness was characterized by both
gastrointestinal symptoms (vomiting, abdominal cramps, diarrhea)
and neurologic symptoms (headache, memory loss). Nausea, loss of
balance, or dizziness were not accepted for a case definition(10)
.

RESEARCH NEEDS

Participants at a Sea Grant sponsored workshop on domoic acid
held at the University of Oregon's Institute of Marine Biology in
February 1992 identified four major priorities for research. 1)
Identify the organism(s) responsible for domoic acid production
and elucidate the factors governing the production of domoic
acid. 2) Establish a phytoplankton field study to examine the
processes that determine the abundance and distribution of
toxin-producing species. 3) Establish routine toxicity monitoring
in an appropriate indicator species, such as razor clams. 4)
Standardize detection methods and train personnel throughout the
affected areas to use these methods(11). The concluding statement
of the workshop participants perhaps best summarizes the need for
continued investigation of the domoic acid toxin: "The history of
nuisance blooms along this coast, and in other regions of the
world, suggest [sic] that ASP will be a recurrent problem.
Knowledge of the source of domoic acid, combined with information
concerning its production, both spatially and temporally, may
lead to a predictive capability for ASP outbreaks. Such
predictions can result in modification of harvesting procedures
and protection of the public. By understanding the problem now,
we may be able to save time, money, and lives in the future(10)."

AVAILABLE HELP

For questions about this document or material therein: Jeff
Jenkins,
Extension Specialist, Oregon State University, (503) 737-5993,
Fax:
(503)  737-0497.    Email:jenkinsj@oes.orst.edu 
or, Pat Thomson, Information Specialist, (503) 737-1802. 
Fax: (503) 737-0497. Email: thomsonp@ucs.orst.edu

INFORMATION ON AGENCY ROLES:
Nick Furman, Oregon Dungeness Crab Commission, 503/267-5810

HUMAN HEALTH CONCERNS: 
Bill Keene, Oregon Health Division, 503/731-4024

SAMPLING AND RESEARCH PROGRAMS:
Mel Eklund, National Marine Fisheries Service-Seattle, 
206/553-7746

OTHER LOCAL RESOURCES:
Ken Hilderbrand, Sea Grant Extension,   503/737-0242; 
Gil Sylvia, Marine Branch Experiment Station, 503/737-0284; 
Jim Golden, Oregon Department of Fish and Wildlife. 503/867-4741

REFERENCES
1. Oregon Health Division, Domoic acid found in Oregon and
Washington shellfish. CD Summary 40(24): 1-2, 1991.

2. Finley, C. Toxin sinks crabbers' Christmas. The Oreg.:
12(15)K1-K9, 1991.

3. Iverson, F.; Truelove, J.; Tryphonas, L.; and Nera, E.A. "The
toxicology of domoic acid administered systemically to rodents
and primates." In: Proceedings of a Symposium, Domoic Acid
Toxicity, Hynie, I. and Todd, E.C.D., Eds. Ottawa, Ontario,
Canada: Canada Diseases Weekly Report, 1990, p. 15-19.

4. U.S. Congress, Office of Technology Assessment, Neurotoxicity:
Identifying and Controlling Poisons of the Nervous System,
Washington, D.C.: U.S. Government Printing Office, 1990.

5. Fryxell, G.A.; Reap, M.E.; and Valencic, D.L. Nitzschia
pungens Grunow f. multiseries Hasle: Observations of a known
neurotoxic diatom. Beih. Nova Hedwig. 100:171-188, 1990.

6. Bates, S.S.; Bird, C.J.; deFreitas, A.S.W.; Foxall, R.;
Gilgan, M.; Hanic, L.A.; Johnson, G.R.; McCulloch, A.W.; Odense,
P.; Pocklington, R.; Quilliam, M.A.; Sim, P.G.; Smith, J.C.;
SubbaRao, D.V.; Todd, E.C.D.; Walter, J.A.; and Wright, J.L.C.
Pennate diatom Nitzschia pungens as the primary source of domoic
acid, a toxin in shellfish from Eastern Prince Edward Island,
Canada. Can. J. Fish. Aquat. Sci. 46:1203-1215, 1989.

7. Bates, S.S.; deFreitas, A.S.W.; Milley, J.E.; Pocklington, R.;
Quilliam, M.A.; Smith, J.C.; and Worms, J. Controls on domoic
acid production by the diatom Nitzschia pungens f. multiseries in
culture: Nutrients and irradiance. Can. J. Fish. Aquat. Sci. 48:
1136-1144, 1991.

8. Oregon Health Division, Spring clamming doubtful - domoic acid
persists. CD Summary 41(9):2, 1992.

9. Fryxell, G.A.; Reap, M.E.; Roelke, D.L.; Cifuentes, L.A.; and
Valencic, D.L. "Confirmed presence of neurotoxin-producing diatom
around Galveston, Texas." In: Proceedings Galveston Bay
Characterization Workshop, February 21-23, 1991, Shipley, F.S.
and Kiesling, R.W., Eds. Galveston, TX: The Galveston Bay
National Estuary Program, 1991.

10. Perl, T.M.; Bedard, L.; Kosatsky, T.; Hockin, J.C.; Todd,
E.C.D.; McNutt, L.A.; and Remis, R.S. "Amnestic shellfish
poisoning: a new clinical syndrome due to domoic acid." In:
Proceedings of a Symposium, Domoic Acid Toxicity, Hynie, 1. and
Todd, E.C.D., Eds. Ottawa, Ontario, Canada: Canada Diseases
Weekly Report, 1990, p. 7-8.

11. Final Report Domoic Acid Workshop, Oregon Institute of Marine
Biology, Wood, A.M. and Shapiro, L., Eds., Feb. 21-23, 1992,
Charleston, OR: Oregon Institute of Marine Biology, University of
Oregon, 1992.

12. Gilligan, M.W.; Burns, B.C.; Landry, G.J.; "Distribution and
magnitude of domoic acid contamination of shellfish in Atlantic
Canada during 1988." In: Toxic Marine Phytoplankton, Granelk, E.;
Sundstrom, B.; Edler, L.; Anderson, D. M. Eds. (Elsevier, New
York, 1990).

13. Didier, A. May 5th Domoic Acid Meeting Summary, Portland,
OR:Pacific States Marine Fisheries Commission, 1992.

14. Rogers, C.G. and Boyes, B.G. Evaluation of the genotoxicity
of domoic acid in a hepatocyte-mediated assay with V79 Chinese
hamster lung cells. Mutat. Res. 226:191-195, 1989.

15. Selected Washington State domoic acid reports from fall
1991/winter 1992, Eugene, OR:Department of Biology, University of
Oregon, 1992.

16. Ohfune, Y. and Tomita, M. Total synthesis of (-)-domoic acid.
A revision of the original structure. J. Am. Chem. Soc.
104:3511-3513, 1982.

17. Wright, J.L.C.; Bird, C.J.; deFreitas, A.S.W.; Hampson, D.;
McDonald, J.; and Quilliam, M.A. "Chemistry, biology and
toxicology of domoic acid and its isomers." In: Proceedings of a
Symposium, Domoic Acid Toxicity, Hynie, I. and Todd, E. C. D.,
Eds . Ottawa, Ontario, Canada: Canada Diseases Weekly Report,
1990, p. 21-26.

18. Lawrence, J.F. and Menard, C. Determination of marine toxins
by liquid chromatography. Fresenius' J. Anal. Chem. 339:494-498,
1991.

19. Newsome, H.; Truelove, J.; Hierlihy, L.; and Collins, P.
Determination of domoic acid in serum and urine by immunochemical
analysis. Bull. Environ. Contam. Toxicol. 47:329-334, 1991.

20. Takemoto, T. and Daigo, K. Constituents of Chondria armata.
Chem. Pharm. Bull. 6(5):578-580, 1958.

21. Olney, J.W. "Excitotoxicity: an overview." In: Proceedings of
a Symposium, Domoic Acid Toxicity, Hynie, I. and Todd, E.C.D.,
Eds. Ottawa, Ontario, Canada: Canada Diseases Weekly Report,
1990, p. 47-58.

22. Zatorre, R.J., "Memory loss following domoic acid
intoxication from ingestion of toxic mussels." In: Proceedings of
a Symposium, Domoic Acid Toxicity, Hynie, I. and Todd, E.C.D.,
Eds. Ottawa, Ontario, Canada, Canada Diseases Weekly Report,
1990, pp. 101-104.

23. Eastaugh, J. and Shepherd, S., Infectious and toxic syndromes
from fish and shellfish consumption, a review , Arch. Intern.
Med. 140:1735-1740, 1989.

24. Sheldon Wagner, M.D., Dept. of Agricultural Chemistry, Oregon
State University, Corvallis, OR, private communication (June 15,
1992).

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Printed January 1992