FDA Issues Warning Over Paralytic Shellfish Poisoning

FDA Issues Warning Over Paralytic Shellfish Poisoning


Certain oysters, clams, and other shellfish harvested in Oregon and Washington could be contaminated with dangerous paralytic toxins, according to the Food and Drug Administration (FDA).

In a notice posted on June 5, the agency said the affected shellfish could contain high levels of a certain toxin that, when ingested, causes paralytic shellfish poisoning (PSP).

About 30 minutes after eating shellfish contaminated with this paralytic toxin, people may experience symptoms such as tingling or numbness in their mouth, arms, or legs, dizziness, headache, or temporary paralysis in their extremities. In very rare cases, the toxin may cause life-threatening paralysis of the respiratory system.

The Oregon and Washington state departments of health first alerted the FDA to the issue on May 30.

Oregon issued a recall of oysters and bay clams harvested in Netarts Bay and Tillamook Bay anytime on or after May 28. The state of Washington recalled all shellfish harvested in multiple regions of Willapa Bay—the exact recall dates depend on the specific growing area, though they range between May 26 and May 30.

The Oregon clams and oysters exposed to high amounts of paralytic toxins were shipped to restaurants and food retailers in Oregon and New York, and possibly contaminated shellfish harvested in Washington was distributed in Arizona, California, Colorado, Hawaii, Nevada, Oregon, and Washington. 

However, the FDA said the recalled shellfish could’ve also been shipped to other states. The agency is waiting for more information on where the harvested shellfish was distributed and said it will update the safety alert when it knows more.

Restaurants and food retailers who may have received clams, oysters, or other shellfish from these specific regions should not serve or sell them and should discard them, the FDA recommended. The same is true for consumers who think they may have purchased contaminated shellfish.

The FDA did not mention any illnesses in connection to shellfish sold in restaurants or by commercial retailers. However, at least 21 people got sick with PSP after consuming mussels recreationally harvested off the Oregon coast in late May. No illnesses have been reported in Washington, though recreational shellfish harvesting is also closed in certain parts of the state.

If a person thinks they’re experiencing any symptoms of PSP after consuming shellfish, they should reach out to their healthcare provider.

Here’s what experts had to say about PSP and how to stay safe while enjoying oysters, clams, and shellfish this summer.

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The paralytic toxins that can contaminate shellfish come from the algae they feed on, said Courtney Temple, MD, assistant professor of emergency medicine at Oregon Health and Science University and medical toxicologist at the Oregon Poison Center. 

“Paralytic shellfish poisoning typically occurs from ingesting shellfish mollusks that are filter feeders,” she told Health. “[They] are contaminated by naturally occurring marine toxins, produced by algae.” 

More specifically, PSP is often linked to a phytoplankton called Alexandrium, which can produce saxitoxin, a neurotoxin, added Vera Trainer, PhD, marine program director and research scientist at the University of Washington Olympic Natural Resources Center.

This specific alga is often found in coastal waters in the Pacific Northwest, Trainer told Health, but in the summer especially, it can bloom—posing a risk for people consuming shellfish.

“We typically see events like this during times of harmful algal blooms,” Temple explained. “There may be varying degrees of this marine algae during different time periods throughout the year, but it’s really this period of robust overgrowth that leads to excessive accumulation within the shellfish that makes it dangerous for consumption.”

It’s typical for the Pacific Northwest to see some beach closures due to unsafe levels of paralytic shellfish toxin throughout the summer months, Temple and Trainer said. However, the scope of this current issue is out of the ordinary.

“Recalls are not common,” said Trainer. “This is one of the largest events on the outer coast of the [U.S.] However, there are often closures due to PSP toxins in bivalve shellfish in Puget Sound, Washington.” 

The same goes for Oregon: “We typically don’t see this number of closures, and we certainly haven’t seen a cluster like this in Oregon for quite some time. So now we have nearly 30 patients who have had some degree of symptoms from this toxin,” Temple added.

People run the risk of developing PSP when they consume clams, oysters, or other shellfish that have high levels of saxitoxin or another paralytic toxin. 

These paralytic toxins can affect a person’s tissues and cause symptoms that can vary quite significantly in severity. 

“Symptoms typically begin about 30 minutes after eating the [contaminated] shellfish, and most of them involve some component of stomach upset—so nausea, vomiting, diarrhea—and that is along with numbness or tingling around the lips or mouth,” Temple explained.

These mild cases are the most common, she added. There’s no antidote or treatment for PSP, but most people eventually pass the toxin from their bodies and recover with no lingering effects. 

However, certain PSP cases can be more serious. It can be hard to determine who is more likely to develop a severe case, Temple said, though eating more contaminated seafood is risky. 

“[PSP] does tend to be dose-related,” she explained. “For one person who eats one clam or mussel versus someone who eats 30 clams or mussels, that person who’s ingested more is more likely to have more severe symptoms.”

In these severe instances, PSP patients may experience “profound weakness, difficulty breathing, and then eventual paralysis that would require admission to an intensive care unit,” Temple said. Severe cases could also lead to more lingering or residual effects from the toxin, she added, or very rarely, can lead to asphyxiation and death.

As common as saxitoxin-producing algae are, experts agreed people don’t need to be too concerned about getting sick with PSP while enjoying clams, oysters, or their other favorite shellfish

“There is active surveillance that’s always taking place along the coast—especially in the Pacific Northwest, where there is a risk of several different kinds of marine toxins,” Temple explained. “Shellfish, mussels, clams, oysters—those are all tested to ensure that the levels of saxitoxin do not exceed the threshold for consumption.”

Because of this surveillance, Trainer said there’s little risk of contracting PSP from shellfish at a restaurant or from one you harvested locally, so long as there isn’t an active warning or beach closure posted.

However, people should do their homework and check for beach closures before harvesting shellfish recreationally, especially because shellfish contaminated with toxins may look, smell, and taste normal.

“People should look at their local health departments website before harvesting shellfish recreationally,” said Trainer. “The public should be very cautious now harvesting any shellfish recreationally on the U.S. West Coast and Alaska. There are some very high levels of toxins in bivalve shellfish right now.”

And in addition to being mindful of where your shellfish is coming from, it’s also important to seek care and call your state poison center if you do think you might be sick with PSP, said Temple.

“[If] they are experiencing symptoms like nausea, vomiting, tingling, numbness in the mouth or face, they should seek medical attention as soon as possible,” she advised. “We can certainly give further guidance, and we are in constant contact with the health authorities in the state to continue reporting and monitoring for additional cases.”

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