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How infectious diseases are spread and simple and practical advice for preventing the spread of infection in the home and community
There are four main types of poisoning that can result from eating fish. See below the relevant type of poisoning for information including signs, symptoms, diagnosis and treatment.
Food poisoning is a notifiable condition1
Ciguatera poisoning is a form of food poisoning caused by eating warm water ocean fish that have ciguatera poison (toxin). The toxin is produced by a small organism called a dinoflagellate, which attaches to algae in warm ocean water reef areas. Small plant eating fish eat this algae, and the toxin then accumulates and is concentrated in larger predatory fish. Many species of fish have been known to cause ciguatera poisoning in humans.
The toxin does not affect the appearance, odour or taste of the fish and is not destroyed by cooking, refrigeration or freezing.
Symptoms usually occur within 1 to 24 hours of eating a toxic fish and include:
Seek medical attention at the onset of symptoms.
Diagnosis is confirmed by the detection of ciguatoxin in fish linked to the case of poisoning.
People recovering from ciguatera fish poisoning should avoid eating warm water ocean fish for at least 6 months, and avoid alcohol for at least 3 months.
Avoid eating large warm water fish, especially the head, roe, liver and other internal organs where ciguatera toxin is more concentrated.
Histamine poisoning can be caused by eating spoiled fish of the:
If fish are caught in warm areas and are not refrigerated properly, a chemical called histidine, that exists naturally in man fish, can break down to histamine which causes symptoms within a few hours of eating the fish.
Symptoms include:
These symptoms usually resolve within 12 hours with no long term effects.
Diagnosis is confirmed by detection of histamine in fish linked to the case of poisoning. In severe cases, treatment with antihistamines may be effective.
Fish should be chilled and properly refrigerated as soon as possible after being caught to prevent histamine formation.
Some organisms present in seawater and ingested by shellfish may produce a toxin. These organisms are particularly numerous during algal blooms or ‘red tides’. Symptoms occur within minutes to hours after eating the shellfish.
Paralytic shellfish poisoning can be very serious and can sometimes cause death.
Symptoms may begin with tingling around the mouth, face, fingers and toes.
Paralytic symptoms usually settle within a few days, but in severe cases, affected people may stagger and may not be able to talk, swallow, move or breathe.
Neurotoxic shellfish poisoning has similar symptoms to ciguatera poisoning, but is usually less severe and lasts only a few days.
Amnesic shellfish poisoning can be serious, causing vomiting, abdominal cramps and diarrhoea, usually within a day of eating the affected shellfish. Confusion, amnesia (loss of memory) and coma may follow in severe cases. The amnesia may be permanent.
Fish caught during algal blooms or during warnings not to fish should not be eaten.
Diagnosis is confirmed by detection of toxins in implicated shellfish.
(time between exposure and developing symptoms)
Symptoms may occur within minutes to 2 hours after consuming the affected shellfish
This is caused by eating fish belonging to the escolar and oilfish groups. These fish have a high wax ester (oil) content. In humans, these wax esters cannot be digested and may accumulate in the bowel causing oily diarrhoea.
Symptoms normally include the sudden onset of watery and oily diarrhoea with abdominal cramps. Nausea, headache and vomiting have also been reported.
Diagnosis is made by testing the implicated fish for oil types, concentration, and by identification of the type of fish.
(time between exposure and developing symptoms)
The average is about 2 to 2½ hours, but can range from 1 to 90 hours. The illness lasts for an average of 22 to 24 hours, with a range from 5 to 78 hours.
Seafood retailers are encouraged to display signs advising that escolar and oilfish might cause symptoms.
1 – In South Australia the law requires doctors and laboratories to report some infections or diseases to SA Health. These infections or diseases are commonly referred to as 'notifiable conditions'.