Shellfish Poisoning

“Paralytic fish poisoning “

“Neurotoxic shellfish poisoning”

“Amnesic shellfish poisoning”

“Diarrhetic shellfish poisoning”

Shellfish poisoning is an illness contracted from eating shellfish like mussels, clams, scallops and oysters contaminated with varied toxins that result in different symptoms depending on the toxin involved. The toxins are saxitoxin & gonyautoxin with paralytic fish poisoning, brevetoxin with neurotoxic shellfish poisoning, dinophysistoxin with diarrrhetic shellfish poisoning and domoic acid with amnestic shellfish poisoning.

Symptoms include tingling around the mouth and limbs, nausea and vomiting, wobbly walking, paralysis, memory loss or diarrhea

Shellfish acquire high concentrations of these toxins during periods of algal blooms referred to as ‘red tide” and can remain toxic for weeks after. The toxins are not neutralized by heat; therefore cooking does not eliminate the risk of disease.

Authorities routinely screen shell fish harvest areas for toxins and prohibit harvest if levels are high. However, recreational shellfish gatherers who ignore or are not aware of this end up contracting the illness.

Where does it occur?

It occurs worldwide wherever shellfish are harvested but more common in colder waters above and below 30 degrees north and south latitudes.

In the United States coastal New England, Florida, Texas, Washington, Oregon and California are states that are commonly affected.

How is it transmitted?

By ingestion of shellfish like mussels, clams, scallops and oysters.

Is it contagious from person to person?

It is not contagious from person to person.

What is the risk for travelers?

The risk is generally low. It is higher if ingesting shellfish during outbreaks of algae blooms – ‘red tide’ that carries the toxins.

How soon after exposure will one develop symptoms?

One develops symptoms within a few hours to days after ingestion.

What are the signs and symptoms?

Paralytic shellfish poisoning:

Symptoms occur within hours with onset of numbness and tingling around the lips, arms and legs with nausea, vomiting and diarrhea. In severe cases one progresses to unsteady walk;like a drunk, difficulty swallowing or speaking, paralysis of the muscles of breathing leading to death.

Neurotoxic shellfish:

Symptoms occur within hours with onset of numbness and tingling around the lips, arms and legs, muscle pain with nausea, vomiting and diarrhea. One can also see dizziness and unsteady walking but symptoms are mild and resolve completely within days.

Amnesic shellfish poisoning:

Symptoms are of nausea, vomiting, diarrhea, stomach cramps and loss of short term memory. The memory problems may persist for months after along with some tingling or numb sensations and weakness of muscles.

Diarrhetic shellfish poisoning:

Symptoms are nausea, vomiting, diarrhea and stomach pains.

Are there any lab tests to diagnose the illness?

There are no specific lab tests for patients. However toxins can be measured in implicated shellfish.

Is there any treatment?

There is no specific treatment, measures are entirely supportive.

What preventive measures can be taken?

Avoid eating shellfish during outbreaks of algae blooms or “red tide”.

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