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Marine Toxins

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What is the most common type of fish poisoning in the US?
Scombroid (Histamine Fish Poisoning)
Where does Scombroid occur?
Primarily in coastal areas, year round
How does Scombroid occur?
Consumption of improperly stored/packaged fish with high levels of histidine (mahi mahi, albacore, mackeral, blue fin tuna)
- Bacterial overgrowth (? Klebsiella) converts histidine to histamine
What is the onset of Scombroid?
RAPID
- Minutes to 1 hour
What are the symptoms of Scombroid poisoning?
Similar to histamine reaction
- Burning, flushing, tachycardia, palpitations, headache, dizziness, abdominal pain, diarrhea
- Severe cases: urticaria, bronchospasm
What is the usual clinical course of Scombroid?
Usually resolves in a few hours, not life threatening
What is the treatment for Scombroid?
Anti histamines, H1 / H2. Epinephrine can be given for severe reactions
Where does Ciguatera occur?
US: Hawaii and Florida
What are the symptoms of Ciguatera?
Abdominal cramps, nausea, vomiting, diarrhea preceeded or followed by numbness and paresthesias of the lips, tongue and throat.
Malaise, HA, pruritis, dry mouth, metallic taste, myalgias, arthralgias, blurred vision, photophobia and transient blindness have also been reported.

Severe: Bradycardia, reversal of hot/cold, hypotension, CN palsies
What are the characteristic findings in Ciguatera?
- Sharp shooting pains in the legs with loose feeling teeth
What is the natural course of illness in Ciguatera?
Duration of illness is from few days to months
What treatment is available for Ciguatera?
Usually supportive, maybe mannitol within 48 hours, mechanism unknown
What is the most common type of shellfish poisoning?
Paralytic shellfish poisoning
How does Ciguatera occur?
Ciguatera toxin produced by certain dinoflagellates
- Toxin accumulates in larger reef fish in food chain that feed on these algae.
Where does paralytic shellfish poisoning occur?
Commonly associated with red tides, usually warmer weather - Sporadic outbreaks Europe, Asia, Africa, and the Pacific Islands
- US: Above 30 degrees N and below 30 degrees S latitude (New England, West Coast)
How does PSP occur?
Caused by certain neurotoxic substance in dinoflagellates, one of which is known as saxitoxin
- Bivalve mollusks (mussels, clams, scallops, oysters, crabs) feed on these dinoflagellates and concentrate in their flesh but do not affect them.
What are the symptoms of PSP?
- Occurs within 5 mins to 4 hrs of ingestion.
- Sxs usually characterized by paresthesias of the mouth, lips, face and extremities.
- Severe cases: dyspnea, dysphagia, muscle weakness or frank paralysis, ataxia, and respiratory insufficiency may occur. - Respiratory failure may occur during the first 12 hrs of illness - Some pts have nausea, vomiting and diarrhea.
What is the natural course of PSP?
Improve after 12 hours and are asymptomatic in a few days.
- Severe cases, fatality rate as high as 12%
- Death may occur within 2-12 hrs without ventilatory support
Where does Neurotoxic Shellfish Poisoning (NSP) occur?
Associated with red tides, occurs in gulf and Atlantic coasts of Florida
How does NSP occur?
Several poorly characterized neurotoxins produced by a dinoflagellate (spp Gymnodidium), are taken up by shellfish.
- Toxins stimulate postganglionic cholinergic nerve fibers and possibly increase sodium channel permeability.
What are the symptoms of NSP?
Mlder than with PSP.
Onset of sxs is usually within 5 mins to 4 hrs after ingestion.
- Presenting sxs: gastroenteritis; rectal burning; paresthesias of the face, trunk, and limbs; myalgias; ataxia; vertigo; and reversal of hot/cold sensation. Very similar to ciguatera poisoning but without the paralysis.
What is the course of NSP illness and treatment?
Usually lasts 1 hour to 72 hours, treat supportively
How does Amnesic Shellfish Poisoning occur?
Caused by a toxin called domoic acid, produced by a dinoflagellate called Nitzschia pungens and concentrated in the flesh of mollusks.
Where does domoic acid damage the brain?
Bilateral destruction of the hippocampus
What are the signs and symptoms of ASP?
Initial sxs are usually nonspecific and include vomiting, abd cramping, diarrhea.
- Headache, confusion, amnesia, coma, and cardiovascular instability follow within hours in severe cases.
- Signs tend to occur in older persons and in persons with underlying renal disease.
What is the usual course of infection with ASP?
Duration of the sxs, particularly amnesia can be few days to permanent.