Ciguatera Fish Poisoning

Ciguatera fish poisoning is reported in Hong Kong from time to time, so what is ciguatoxin? What are the principal symptoms of ciguatoxin poisoning? How to prevent ciguatoxin poisoning?

Ciguatoxin originates from a toxic marine microorganism, dinoflagellate, which lives on dead coral reef and algae. In fact, coral reef fish is not toxic, but fish eating the algae accumulates the ciguatoxins, and the effect is magnified through the food chain so that larger predatory fish is more toxic. Ciguatoxin usually accumulates in the head, skin, viscera and roe of the fish. Ciguatoxin does not cause any harm to the coral reef fish. Hence, ciguatoxic fish cannot be identified by its appearance, odour or texture. As the toxin is highly stable, it cannot be destroyed by cooking, refrigeration, drying and digestion.

People affected may show symptoms of mouth and limbs numbness, vomiting, diarrhoea, nausea, abdominal pain and pain of the joints and muscles. If excessive toxin was consumed, the circulatory and nervous systems would be affected.

According to past records of ciguatera fish poisoning cases reported in Hong Kong, fish species which are more likely to contain ciguatoxins include Moray Eel, Potato Grouper, Speckled Blue Grouper, Tiger Grouper, High Fin Grouper, Hump Head Wrasse, Areolated Coral Grouper, Black Saddled Coral Grouper, Lyretail, Black Fin Red Snapper, Flowery Grouper and Leopard Coral Grouper.

To prevent ciguatera fish poisoning, members of the public should observe the following measures:

Purchase

• Buy coral reef fish from reputable and licensed seafood shops. Do not buy the fish if in doubt.

Consumption

• Consume less coral reef fish, especially marine fish over three catties.
  
• Consume small amount of coral reef fish at any one meal and avoid having a "whole fish feast" in which all the dishes come from the same big coral reef fish.
  
• Avoid eating the head, viscera, skin, and roe of coral reef fish which usually have higher concentration of toxin.
  
• When eating coral reef fish, avoid consuming alcohol, peanuts or beans as they may aggravate ciguatera poisoning.
  
• Members of the public suffered from ciguatoxin poisoning should refrain from coral reef fish. The intoxication would sensitize the patients and they will suffer from ciguatoxin poisoning even if they are exposed to a lower concentration of toxin.
  
• Seek medical treatment immediately when symptoms of ciguatera fish poisoning appear. The unfinished fish should be brought to FEHD for testing.