California mussels may contain poison — CDPH says should not be harvested for human consumption

LITTLE RIVER, 5/5/21 — The seasonal quarantine of California mussels, which may contain deadly poison, began May 1. The California Department of Public Health announced last week that it is no longer safe to gather mussels for human consumption, and that they should only be harvested for bait. Starting on May 1, annual quarantine of sport harvested mussels officially began, with the stated purpose of protecting people against domoic acid, or “paralytic shellfish poisoning,” which is potentially deadly.

Here is the press release from the California Department of Public Health:

Annual Quarantine of Sport-Harvested Mussels Begins May 1

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California mussels may contain poison – CDPH announces beginning of annual quarantine

SACRAMENTO – The California Department of Public Health (CDPH) today announced the annual quarantine of sport-harvested mussels gathered along the California coast. The quarantine begins May 1 and applies to all species of mussels that are recreationally harvested for human consumption along the California coast, including all bays and estuaries. During the quarantine, mussels may only be harvested for use as bait. The quarantine is in place to protect the public against poisoning that can lead to serious illness, including coma and death.  

The quarantine is designed to prevent paralytic shellfish poisoning (PSP) and domoic acid poisoning, also known as amnesic shellfish poisoning, in people who might otherwise consume sport-harvested mussels. Both of these syndromes are from naturally occurring toxins produced by certain phytoplankton consumed by shellfish, including mussels and clams. Cooking does not destroy the toxins. 

Historically the majority of human cases of PSP illnesses occur between spring and fall. In California, PSP is extremely rare due to the efforts put forth by CDPH to protect the public against poisoning. There have been no reported human cases of domoic acid poisoning 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.

Symptoms of mild domoic acid poisoning may include vomiting, diarrhea, abdominal cramps, headache and dizziness. In severe cases, the victim may experience trouble breathing, confusion, disorientation, cardiovascular instability, seizures, excessive bronchial secretions, permanent loss of short-term memory, coma or death.

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 safe. 

More information about the quarantine, PSP and domoic acid 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 or view the recreational bivalve shellfish advisory interactive map. For additional information, please visit the CDPH Marine Biotoxin Monitoring Web page.