Marine toxins

Marine toxinsDr.Shaleesha A. Stanley

Prof. & HeadDept. of Biotechnology

Jeppiaar Engineering College

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• Marine toxins are naturally occurring chemicals that can contaminate certain seafood.

• The seafood contaminated with these chemicals frequently looks, smells, and tastes normal, but can

make people sick if they eat it.

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There are three main types of marine toxins

• Those caused by eating fish, including: – Scombrotoxic fish poisoning – Ciguatera poisoning – Tetrodotoxin poisoning (fugu or pufferfish poisoning)

• Those caused by eating shellfish, including: – Paralytic shellfish poisoning (PSP) – Red tide/neurotoxic shellfish poisoning (NSP) – Diarrheic shellfish poisoning (DSP) – Amnesic shellfish poisoning (ASP)

• Those caused by contaminated water, including: – brevetoxins – Blue-green algae (Cyanobacteria) – Pfiesteria and the Pfiesteria-like organisms (PLOs)

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Scombrotoxic fish poisoning

• Also known as histamine fish poisoning• is caused by bacterial spoilage of certain finfish such as tuna,

mackerel and other fish. • As bacteria break down fish proteins, byproducts such as histamine

and other substances that block histamine breakdown build up in fish.

• Eating spoiled fish that have high levels of these histamines can cause human disease.

• Symptoms begin within 2 minutes to 2 hours after eating the fish. The most common symptoms are rash, diarrhea, sweating, headache, and vomiting. Burning or swelling of the mouth, abdominal pain, or a metallic taste may also occur.

• The majority of patients have mild symptoms that resolve within a few hours.

• Treatment -antihistamines or epinephrine

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Ciguatera poisoning

Ciguatera is caused by eating contaminated tropical reef fish. Ciguatoxins are actually produced by microscopic sea plants called

dinoflagellates. Dinoflagellates are single-celled marine organisms that are extremely diverse. The toxins become progressively concentrated as they move up the food

chain from small fish to large fish that eat them, and reach particularly high concentrations in large predatory tropical reef fish.

Barracuda are commonly associated with ciguatoxin poisoning, but eating grouper, sea bass, snapper, mullet, and a number of other fish that live in tropical oceans has caused the disease.

Ciguatoxin and the closely-related maitotoxin are both produced by dinoflagellates and cause symptoms by interfering with ion channels on cell membranes. Ciguatoxin opens sodium channels and maitotoxin opens calcium channels, disrupting the signaling between nerves and muscles.

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• Common nonspecific symptoms include nausea, vomiting, diarrhea, cramps, excessive sweating, headache, and muscle aches.

• Treatment is generally supportive; mannitol (an osmotic diuretic) may be used to increase urine output

Ciguatera poisoning

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Tetrodotoxin poisoning

• Tetrodotoxin causes this type of poisoning; • it is found the liver, gonads, intestines, and skin of pufferfish (fugu),

as well as in less-commonly eaten animals like parrotfish, frogs, octopus, starfish, angelfish, and crabs

• The disease is potentially deadly. • Symptoms include numbness of the lips and tongue, tingling in the

body, and a sensation of lightness. Nausea and vomiting, diarrhea, and belly pain may occur.

• Treatment is supportive, and may include giving the person charcoal, pumping the stomach, giving IV fluids, and placing them on a ventilator in severe cases. There is no antidote

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ShellfishParalytic shellfish poisoning

Paralytic shellfish poisoning is caused by a different dinoflagellate with a different toxin than the one responsible for ciguatera poisoning.

These dinoflagellates have a red-brown color, and can grow to large numbers that they cause red streaks to appear in the ocean called "red tides."

This toxin is known to concentrate within certain shellfish that typically live in the colder coastal waters of the Pacific states

Shellfish that have caused this disease include mussels, cockles, clams, scallops, oysters, crabs, and lobsters. Saxitoxin is the poisonous molecule in these organisms that causes paralysis by blocking sodium channels necessary for muscles to contract.

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Amnesic shellfish poisoning

• Amnesic shellfish poisoning is a rare syndrome caused by a toxin made by a microscopic, red-brown, salt-water plant, or diatom called Nitzchia pungens.

• The toxin produced by these diatoms is concentrated in shellfish such as mussels and causes disease when the contaminated shellfish are eaten.

• The active molecule involved in amnesic shellfish poisoning is domoic acid, and works by stimulating glutamate receptors in the central nervous system.

• Patients first experience gastrointestinal distress within 24 hours after eating the contaminated shellfish.

• Other reported symptoms have included dizziness, headache, disorientation, and permanent short-term memory loss.

• In severe poisoning, seizures, focal weakness or paralysis, and death may occur.

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Contaminated water The dinoflagellate Karenia brevis annually blooms These blooms are called red tides. When it does so, it releases brevetoxins into the air. This leads to fish and marine mammal deaths as

well as irritation of the respiratory tract in humans. These are the same brevetoxins that lead to

neurotoxic shellfish poisoning in contaminated shellfish

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Blue-green algae (Cyanobacteria) Blue-green algae are actually a type of bacteria called cyanobacteria. Ex. : Anabaena, Aphanizomenon, and Microcystis species produce

toxins sporadically, while Cylindrospermopsis produce it all the time. These algae, also known as pond scum, have been known to kill

livestock that drink the water in which the algae are growing Blue-green algae can produce both neurotoxins, which affect the

nervous system, and hepatotoxins, which affect the liver. These toxins can quickly kill livestock who drink contaminated water.

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Brevetoxins

• Brevetoxins are known to bind to site 5 of voltage-gated sodium channels in nerve cells, leading to channel activation.

• This leads to disruption of normal neurological processes and causes the illness clinically described as neurotoxic shellfish poisoning(NSP).

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Cyanopeptolins

Cyanopeptolins are cyclic non-ribosomal

peptides isolated from various cyanobacteria.

Okadaic Acids• Okadaic acid is a polyether from the dinoflagellate that is

the causative agent of diarrhetic shellfish poisoning (DSP).

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