Annual Quarantine of Sport-Harvested Mussels Begins

“The quarantine is in place to protect the public against poisoning that can lead to severe illness, including coma and death,” said Dr. Ron Chapman, CDPH director and state health officer. “It is critical that the public honor this quarantine, as toxins found in mussels have no known antidotes. These toxins are not reliably destroyed by cooking.”

This quarantine, which typically starts on May 1 and ends October 31, protects the public from paralytic shellfish poisoning (PSP) and domoic acid poisoning (DAP). Both of these toxins are linked to plankton consumed by filter-feeding animals, including bivalve shellfish, like mussels. The majority of human cases of PSP illnesses occur between spring and fall.

PSP affects the central nervous system, producing a tingling around the mouth and fingertips as soon as a few minutes after eating toxic shellfish. These symptoms are typically followed by a loss of balance, lack of muscular coordination, slurred speech and difficulty swallowing. In severe cases, complete muscular paralysis and death from asphyxiation can occur.

Symptoms of DAP, also known as amnesic shellfish poisoning (ASP), 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.

Commercially harvested shellfish are not included in the annual quarantine. That’s because all commercial shellfish harvesters in California are certified by the state and subject to strict requirements to ensure that all oysters, clams and mussels entering the marketplace are free of toxins.

In Marin County, the health advisory on sport-harvested bivalve shellfish (clams and scallops) other than mussels has been lifted.

More information about the quarantine, PSP and DAP can be found on the CDPH.

For updated information on quarantines and shellfish toxins, call the CDPH Biotoxin Information Line (1-800-553-4133).

“Last year’s toxin levels resulted in extended warnings and quarantines in some areas,” added Chapman. “It’s very important that the public be aware of the current conditions.”