“Don’t let your dinner party turn into tragedy by risking the consumption of sport-harvested mussels,” said CDPH director and State Public Health officer Dr. Karen Smith. “The toxins found in shellfish can kill a person within 30 minutes. There are no known antidotes, and the toxins are not reliably destroyed by cooking.”
The quarantine is designed to prevent paralytic shellfish poisoning (PSP) and domoic acid poisoning (DAP) in people who might otherwise consume sport-harvested mussels. Both of these toxins are linked to plankton consumed by shellfish, including mussels and clams.
Historically, the majority of human cases of PSP illnesses occur between spring and fall. In California, PSP is extremely rare in part due to the efforts put forth by CDPH to protect the public against poisoning. There have been no reported cases of DAP in California.
Early symptoms of PSP include tingling of the lips and tongue, which may begin within minutes of eating toxic shellfish. These symptoms are typically followed by a loss of balance, lack of muscular coordination, slurred speech and difficulty swallowing. In severe poisonings, complete muscular paralysis and death from asphyxiation can occur.
Commercially harvested shellfish are not included in the annual quarantine because all commercial harvesters in California are certified by CDPH and subject to strict testing requirements to ensure that all oysters, clams and mussels entering the marketplace are free of toxins.
In addition to this annual quarantine, consumers are urged not to eat recreationally harvested razor clams from Humboldt and Del Norte counties due to continued high levels of domoic acid. Symptoms of DAP, also known as amnesic shellfish 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 disappear completely within several days. In severe cases, the victim may experience difficulty breathing, confusion, disorientation, seizures, permanent loss of short‑term memory, coma and death.
More information about the quarantine, PSP and DAP can be found on the CDPH Annual Mussel Quarantine - Frequently Asked Questions (FAQ) Web page.
For updated information on quarantines and shellfish toxins, call the CDPH Biotoxin Information Line at 800-553-4133.