Susan Buckley, RN, Director, Public Health
Ira Singh, MPH, Deputy Director
Donald I. Baird, MD, Health Officer

Division of Environmental Health


Date Released: 6/10/2004
Subject: Consumers advised not to eat sport-harvested bivalve shellfish from Humboldt and Del Norte Counties
Contact: Brent Whitener, Vector Control Officer, Environmental Health Division
Phone: (707) 445-6215

The Humboldt County Department of Health and Human Services is advising that consumers should not eat sport-harvested bivalve (two-shelled) shellfish from Humboldt and Del Norte counties because they may be contaminated with domoic acid, a naturally occurring toxin that can cause serious human illness. Dr. Richard Joseph Jackson, public health officer of the California Department of Health Services (CDHS) issued a similar warning today.

Elevated levels of domoic acid, which is produced by microscopic marine algae, have been detected in razor clams in these areas by CDHS.

This warning is in addition to the annual quarantine on the sport-harvesting of mussels along the entire California coastline that took effect April 23 to prevent domoic acid and paralytic shellfish poisoning.

Domoic acid was first identified in 1987 off the coast of Eastern Canada, and first found in California in 1991 at several locations along the coast in samples of mussels, razor clams and other seafood. Domoic acid poisoning can have both immediate and permanent long-term health effects.

Symptoms of domoic acid poisoning can occur within 30 minutes to 24 hours after eating toxic seafood. In mild cases, symptoms may include vomiting, diarrhea, abdominal cramps, headache and dizziness. These symptoms commonly disappear within several days. In severe cases, the individual may experience excessive bronchial secretions, difficulty in breathing, confusion, disorientation, unstable blood pressure and irregular heartbeat, seizures, permanent loss of short-term memory, coma and even death.

Paralytic shellfish poisoning affects the human central nervous system, producing a tingling around the mouth and fingertips within a few minutes to a few hours after eating toxic shellfish. These symptoms are followed by disturbed balance, lack of muscular coordination, slurred speech and difficulty swallowing. In severe poisonings, complete muscular paralysis and death from asphyxiation can occur.

State law prohibits the sale or offering for sale for human consumption of any bivalve shellfish except by a state-certified commercial shellfish harvester or dealer. Shellfish sold by certified harvesters are subject to frequent mandatory testing.

For updates on shellfish biotoxins and quarantines and other information, consumers can call CDHS' toll-free "Shellfish Information Line" at 1/800-553-4133. Additional information may also be obtained by contacting the Environmental Health Division at (707) 445-6215 or toll free at 1-800-963-9241.


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