Over the last decade, Alaska has reported fewer cases of a serious condition caused by consuming contaminated shellfish than in previous years.
But health officials say Alaskans who self-harvest shellfish should still be aware of the risks of paralytic shellfish poisoning.
Katherine Newell, an Epidemic Intelligence Service officer with the Centers for Disease Control and Prevention who is assigned to Alaska’s Division of Public Health, helped put together a new state report tracking cases of PSP in Alaska between 1993 and 2021.
There have been 132 reports of the poisoning in Alaska during that time, including five fatal cases. About 25% of those cases occurred in or near Kodiak, 20% were in Juneau and 14% occurred in Ketchikan, the report found.
The condition, also known as PSP, is a foodborne illness caused by neurotoxins known as saxitoxins, which are produced by harmful algal blooms that shellfish sometimes take into their systems while filter feeding, Newell explained.
When a human ingests the contaminated shellfish, it can be “pretty serious, and sometimes fatal,” Newell said. “It’s a reportable condition in Alaska because of how serious it is.”
Commercially harvested shellfish is tested for the toxin, which is why PSP cases nearly always occur in self-harvested seafood, Newell explained. Contaminated shellfish also tastes and looks the same as non-contaminated seafood, she said. Cooking or freezing the fish makes no difference.
Anyone who experiences symptoms of the condition after consuming shellfish — which include tingling of the lips, tongue, fingers or toes; difficulty swallowing; dizziness; impaired coordination and muscle weakness — is encouraged to contact their medical provider immediately even if their symptoms appear mild, Newell said.
Symptoms can progress very quickly, she added — the incubation period can range from five minutes to 12 hours. Because there is no antitoxin, the treatment is purely supportive measures that may include for severe cases, things like mechanical ventilation, she said.
According to the new report, although PSP cases are uncommon, Alaska has one of the highest PSP case rates in the country.
“This is likely due to a combination of factors including a large coastline, abundant shellfish populations, and environmental conditions conducive to (harmful algal bloom) formation,” the report said.
Over the last three decades, the number of PSP incidents have ranged from zero to 15 incidents annually, the report found.
That variance can be explained by “things like the amount of self-harvested shellfish collecting that’s being done during that year, as well as the number of these harmful algal blooms that have formed and where they have formed relative to population centers,” Newell said.
While most of the cases are reported in the spring and summer months in Alaska, cases have been reported year-round in the state, the report said.
The reasons for the recent decline in reported cases are unclear, the report said, “but might be due in part to declines in subsistence shellfish consumption, improved community awareness of PSP risk, and/or decreased reporting of suspected PSP cases.”
“It’s important to note that the decline in reported cases is not indicative of reduced risk of PSP in Alaska,” Newell said, noting that harmful algal blooms still form every year in the state.