Shellfish Poisoning - Symptoms, Types, and Treatment

Introduction

Shellfish poisoning can affect human health as the toxins from the water accumulate in the shellfish, causing poisoning. Different types of toxins cause 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. Red tides, which are usually associated with the presence of harmful algal blooms, can considerably raise toxin levels in shellfish and are more dangerous to eat during the summer. The poisoning from shellfish can occur after eating oysters, starfish, clams, or mussels containing toxic substances that 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:

• Vomiting.

• Nausea.

• Diarrhea.

• Cramps.

• Abdominal pain.

• Headache.

• Loss of balance.

• Altered perception of temperature.

• Lower blood pressure.

• Low heart rate.

• Metallic taste in the oral cavity or mouth.

• Vertigo.

• Blurred vision.

• Lower back pain.

• Drooling.

• Cough.

• Respiratory mucosal irritation.

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 acidic or heated 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 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 and cardiac dysfunction are also treated.

When Should You Seek Medical Care For Shellfish Poisoning?

While other symptoms may cause discomfort and require medical attention, serious cases include gastrointestinal complications, neurological signs, problems with breathing, muscle weakness, heart problems, and severe headaches. Paralytic shellfish poisoning and domoic acid poisoning might turn fatal if left untreated. The patient should consult a healthcare provider when they cannot take oral fluids if they have a fever, blood-stained diarrhea, or if they note other unfavorable signs. Consult the doctor as soon as possible in any other instances of shellfish poisoning.

How Can We Prevent Shellfish Poisoning?

Shellfish poisoning is a problem in both children and adults. To avoid it, people should only purchase seafood from registered stores, not take raw shellfish, and not eat fish from fertile water bodies because of eutrophication. Many toxins are heat-stable, so cooking shellfish at 100 degrees Celsius until they open or even further for three to five minutes lessens the risk. When experiencing symptoms, seek medical advice and preserve leftover shellfish for sample analysis. The measure is widely important for sustaining the health status of the marine ecosystem.

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.

Conclusion

Shellfish poisoning can affect the population worldwide, mainly during the summer, as many algae and dinoflagellates blood in the seawater cause 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.