Overview: Paralytic Shellfish Poisoning in Alaska

people digging for clamsSubsistance harvesting at Jakolof Bay. Dave Partee/Alaska Sea Grant

Shellfish are harvested along Alaska’s many beaches for subsistence and recreational purposes throughout the year. Before collecting and consuming shellfish in Alaska you should be aware of the risks. Paralytic shellfish poisoning, or PSP, is a serious illness caused from eating shellfish contaminated with toxins from algae. Subsistence and recreationally harvested shellfish, including clams, mussels, oysters, geoducks, scallops, predatory snails, and crab, can contain PSP toxins. If ingested in high enough concentrations, PSP toxins can cause serious illness in humans and can even result in death. No beaches in Alaska are certified as “safe” for recreational and subsistence shellfish harvesting and there is no known antidote for PSP.

You should know

What Is PSP?

Paralytic shellfish poisoning (PSP) is a serious illness that is caused by eating shellfish that have been feeding on microscopic, single-celled dinoflagellate algae (Alexandrium in Alaska) that produce highly poisonous toxins. These PSP toxins, commonly referred to as saxitoxins, are neurotoxins that block the movement of sodium through nerve cell membranes, stopping the flow of nerve impulses. Without the movement of sodium, nerve cells cannot function, causing the PSP symptoms of tingling, numbness, disorientation, paralysis, nausea, respiratory failure, and even death. PSP toxins are estimated to be 1,000 times more toxic than cyanide, and as little as 1 milligram of saxitoxin is enough to kill an adult human. Eating a single shellfish, such as a clam, that is contaminated with PSP toxin has the potential to cause death.

PSP Symptoms

Symptoms can start quickly, within minutes of consuming contaminated shellfish, or they may not appear until hours after consumption. The median time between consuming the shellfish and onset of symptoms is one hour. The progression and intensity of the symptoms vary among individuals and are influenced by the level of toxin present and the amount of shellfish consumed. The first symptom to appear is usually tingling and numbness in the mouth region. In severe cases the muscles of the chest and abdomen can become paralyzed, and if breathing assistance is not provided, respiratory failure can occur. Death can occur within two hours of consuming infected shellfish.

Treatment of PSP

There is no antidote for PSP. In general, supportive measures are the only means of treatment, specifically breathing and cardiac support in severe cases. If you or someone else exhibits PSP symptoms, get medical help immediately.

It is highly recommended that a medical assessment be made as soon as possible after symptoms appear. Symptoms can become more severe over time, and because the amount of PSP toxins consumed is often unknown, progression of the illness is unpredictable. If the level of toxin is high enough to cause respiratory paralysis, the victim will need to be put on a mechanical respirator and given oxygen to help with breathing. Symptoms can resolve completely within hours to days after consuming infected shellfish.

In Alaska, if you or someone you know has PSP symptoms and is in need of rescue or transport by helicopter or boat, you can call the US Coast Guard Rescue Coordination Center at the numbers below.

How to Report a PSP Public Health Emergency

Paralytic shellfish poisoning is a public health emergency. If one case occurs, there will likely be others and reporting even mild cases may save another person’s life. Health care providers and citizens should report any suspected case of PSP immediately to the Alaska Section of Epidemiology. To report, call 907-269-8000 (Monday–Friday, 8 am–5 pm) or 1-800-478-0084 (after hours).

For More Information

Identifying shellfish in Alaska

Paralytic shellfish poisoning

Harmful algal blooms


Alaska Department of Environmental Conservation
555 Cordova Street
Anchorage, AK 99501
(907) 269-7638