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Shelfish Poisoning - Symptoms, Types, and Treatment

Published on Mar 21, 2023   -  4 min read


Shellfish such as oysters, dried fish, shrimps, and crabs can accumulate sea toxins in the human body and cause poisoning. Read the article to know more about it.


Shellfish poisoning can affect human health as the toxins from the water accumulate in the shellfish, causing poisoning. There are different types of toxins causing different types of shellfish poisoning, such as saxitoxin, domoic acid, okadaic acid, and brevetoxins, causing paralytic, amnesic, diarrhetic, and neurotoxic shellfish poisoning, respectively. These toxins in the shellfish are usually associated with algal blooms in the water sources as contaminants. The poisoning from shellfish can occur after eating oysters, starfish, clams, or mussels containing toxic substances which can affect human health. The shellfish feed on these toxins, which can then remain (dinoflagellates) in the tissues and digestive system without causing harm to themselves. Therefore, people should consume shellfish cautiously to avoid poisoning by these harmful toxins.

What Are the Symptoms Caused by Shellfish Poisoning?

The symptoms caused by shellfish poisoning can occur up to 48 hours after consumption and produce symptoms such as:

What Are the Types of Shellfish Poisoning?

Various types of shellfish poisoning are as follows:

  • Neurotoxic Shellfish Poisoning: It is caused after eating mussels or clams and produces symptoms such as diarrhea, nausea, and vomiting. After a few hours, numbness and tingling sensations can be felt by the person on the face, mouth, and lips. Loss of coordination and partial paralysis can also occur. Apart from this, headaches, pupil dilation, heaviness in the chest, slurred speech, and throat irritation occur.

  • Paralytic Shellfish Poisoning: This type of poisoning occurs after 30 minutes of eating seafood containing toxins and causes a tingling sensation and numbness in the mouth, legs, and arms. The condition can also lead to complete paralysis of the respiratory system and partial paralysis of the upper and lower limbs.

  • Amnesic Shellfish Poisoning: This type of shellfish poisoning causes symptoms like vomiting, nausea, and diarrhea within 24 hours of consumption. Severe poisoning can cause short-term memory loss, shock, seizures, and coma.

  • Diarrhoeic Shellfish Poisoning: The most common symptom of shellfish poisoning is diarrhea, followed by vomiting and nausea within 30 to 12 hours of consumption. Recovery from this type of poisoning usually occurs in three days.

What Is the Pathophysiology of Shellfish Poisoning?

  • The paralytic shellfish toxins (saxitoxin) are water soluble and are stable in an acid or heat environment. These toxins are mainly sodium channel blockers and can block the sodium ions by binding with the sodium channels in the neurons.

  • Domoic acid (amnesic shellfish poisoning) can affect the renal system in the human body at smaller doses and produce some neurological symptoms. These toxins affect the neurological function in the brain and activate neurotransmitter agonists, which can lead to calcium influx which further causes degeneration of the cells.

  • Okadaic acid toxin increases the permeability of the cell and sodium secretion by inhibiting the protein phosphatase.

  • Brevetoxin binds with the muscle cells and sodium channels and, thus, lowers the potential of neurons in the brain.

How Is Shellfish Poisoning Diagnosed?

Shellfish poisoning is diagnosed in the following ways:

  • Blood and urine tests.

  • ELISA (enzyme-linked immunosorbent assay).

  • HPLC (high-pressure liquid chromatography).

  • ECG (electrocardiogram).

What Are the Treatment Options for Shellfish Poisoning?

The treatment options for shellfish poisoning include:

  • Diarrheic shellfish poisoning is treated with electrolyte and fluid replacement therapy because of loss of their loss due to diarrhea.

  • Neurotoxic shell poisoning causes breathing difficulty in a person. Therefore, the doctor gives supportive treatment for airway management. Also, bronchodilators, fluid replacements, and supportive therapy are given according to the symptoms and exposure caused.

  • Treatment for amnesic shell poisoning is also supportive of maintaining an airway or respiratory function and other symptoms. In addition, hemodynamic instability is also treated along with cardiac dysfunction.

How Can We Prevent Shellfish Poisoning?

The preventive measures for shellfish poisoning are as follows:

  • First, people should always buy shellfish or any seafood from licensed and reputed shops, especially when they are a traveler and do not know much about the best quality of seafood available in the area.

  • Shellfish poisoning can affect children and adults both; therefore, it should not be consumed raw.

  • People should not consume fish from water sources enriched with nutrients, harmful algae, and plant growth due to eutrophication.

  • Toxins present in shellfish can be resistant to heat. Therefore, one should cook the shellfish at 100 degrees Celsius until the shells of the fish open. Then keep cooking it for the next three to five minutes as it can reduce the risk and kill the toxins causing contamination.

  • Suppose a person experiences any kind of symptoms after eating shellfish. They should consult the nearby healthcare provider for medical help and keep the shellfish leftovers for clinical investigations and testing.

What Is the Differential Diagnosis for Shellfish Poisoning?

The differential diagnosis for shellfish poisoning includes:

  • Carbamate toxicity.

  • Phenytoin toxicity.

  • Gastroenteritis.

  • Botulism.

  • Tetrodotoxin toxicity.

  • Ciguatera toxicity.

  • Scombroid.


Shellfish poisoning can affect the population worldwide, mainly during the summer, as many algae and dinoflagellates blood in the seawater causes red tides. These are very harmful to humans and can lead to many health risks. Shellfish poisoning mainly occurs in seas with warm water because they are heat-stable species; therefore, people should cook fish thoroughly to avoid contaminants from entering the body. In addition, people consuming seafood must gain proper knowledge from the nearest local health authorities about the quality of the seafood to minimize the health risks caused by the toxins present in the shellfish. The symptoms caused by shellfish poisoning can affect the respiratory, neurological, and digestive systems to a large extent and, in some cases, can also lead to long-term memory defects and paraesthesia. Therefore, people experiencing the symptoms after eating shellfish must visit a healthcare provider immediately to seek advice.

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Last reviewed at:
21 Mar 2023  -  4 min read




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