Fishing Info › Fishing Safely
This is one of a series of articles prepared for Fishing Cairns by Dr Deborah Mills, author of the book, Travelling Well, and director of Dr Deb The Travel Doctor travel medicine clinics in Brisbane.
Ciguatera is a poisoning resulting from eating certain fish in particular environments in the Indian Ocean, Pacific Ocean, and The Caribbean.
The poison occurs naturally in algae and plankton, the lower part of the marine food chain. The little fish eat the algae, the big fish eat the little fish, the bigger fish eat the big fish and so on. The effects of the poison are related to the dose you get, so the bigger the fish, the more IT has eaten, and the sicker YOU get.
The locals usually know which fish carry the highest risk.Mackerel caught around mid October in Australia are a classic cause of the condition, as are some Great Barrier Reef and semi-pelagic saltwater fish including red bass, chinamanfish (chinaman cod), paddle tail, snapper, spanish mackerel, moray eels, wrasse, trigger fish, and queenfish. Even coral trout has been incriminated as an occasional carrier.
Captain Cook reported the first case of ciguatera poisoning in the Pacific in 1774 while in the New Hebrides. He suffered poisoning twice, and red bass was thought to be responsible on both times.
Symptoms range from none at all to severe and incapacitating, and come on within one hour, or be delayed for 24 hours or more. The illness lasts for an average of about 8 days, but in some cases symptoms can take months to years to disappear.
The symptoms are very varied.Sweating may be the first sign that something is wrong but the most common symptom is altered sensation around the lips, mouth, tonge and throat. This may be felt as numbness, tingling or even extreme sensitivity, and reversed feelings of heat. The sufferer complains may complain of hot foods feeling cold, and vice versa.
Tingling or itching in the extremities may persist for weeks and be set off by exposure to water or cold. Disturbance of sensation may occur elsewhere in the body, including severe stabbing pain in the genitals (sorry guys!).
Heaviness, weakness, and muscle pains of the body, legs and arms, and a lack of co-ordination may also occur. Gut symptoms of nausea, vomiting, pain in tummy, cramps, abnormal metallic taste, aching of the teeth and a watery diarrhoea may occur. Tightness in the jaw and face muscles have been described.
Tiredness, dizziness and exhaustion may occur and even paralysis of breathing so that life support is required. Alcohol makes the symptoms worse.
No immunity develops after an attack, and in fact the second time around a much smaller dose is required to produce symptoms.
Can it be fatal?
The death rate world wide is reported to be 10-12%; however in Australia it is exceptionally low. It is usually not fatal, although there is a report of 1500 men dying from ciguatera poisoning during the British naval expedtion against Mauritius in 1748
It is not possible to detect the toxin before eating the fish, which appear quite healthy and the taste and smell of the flesh is not affected.
Probably the simplest precaution is not to eat the fish if your hands feel numb after cleaning it, or if there is any suggestion of a stinging sensation after skinning or filleting it.
Some authorities recommend feeding the viscera of the fish to a cat and confine it for observation. However, the cat may vomit, become uncoordinated, or even die within 48 hours. This is obviously extremely hard on the poor cat, and a more humane option should be entertained first. Testing a small amount of fish flesh on a healthy adult in your party the night before is a better solution, if you can find a willing victim.
A few other avoidance measures include:
- Ask the locals as the toxic fish may be confined to a narrow area like one side of a small island.
- Avoid the biggest fish of the catch.
- At no time eat or handle red bass, chinaman fish, paddle tail, or moray eels.
- If still in doubt, stick to safe fish like mullet, whiting, bream and flathead.
The poison is very stable and resistant to heat and drying, so cooking does not deactivate the poison. Soaking the fish won't work either as the poison is not water soluble.
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