31 May 2011
The Centre for Health Protection (CHP) of the Department of Health today (May 31) is investigating four suspected ciguatoxin poisoning cases affecting nine people who have consumed coral reef fish.
The first case involved a 38-year-old woman. She developed symptoms of ciguatoxin poisoning including limb numbness and muscle pain about 20 hours after eating a fish during dinner at home on May 29.
She sought medical treatment at North District Hospital. No hospitalisation was required and she is now in stable condition.
The second case involved a man and three women aged between 14 and 50. They developed symptoms of ciguatoxin poisoning including limb numbness, nausea, dizziness and weakness about three to 11 hours after eating a fish during dinner at home on May 29.
They sought medical treatment at Queen Elizabeth Hospital. One of them required hospitalisation and they are now in stable condition.
The third case involved a man and a woman aged 60 and 54 respectively. They developed symptoms of ciguatoxin poisoning including perioral numbness, limb numbness, weakness and diarrhea about five to seven hours after eating a fish during dinner at home on May 30.
One of them sought medical treatment at North District Hospital and required hospitalisation. Both of them are now in stable condition.
The fourth case involved a man and a woman aged 58 and 48 respectively. They developed symptoms of ciguatoxin poisoning including dizziness, perioral numbness, limb numbness, weakness and diarrhoea about half an hour to eight hours after eating a fish during dinner at home on May 30.
One of them sought medical treatment at North District Hospital and required hospitalisation. Both of them are now in stable condition.
Investigation revealed that the incriminated fishes in the above cases were purchased from a wet market in Sheung Shui.
A CHP spokesman said ciguatera fish poisoning is not uncommon in tropical areas. It is mainly associated with the consumption of a big coral reef fish which has accumulated the toxin in its body, in particular in internal organs, through eating small fish that consumed toxic algae in coral reef seas.
The larger fish is therefore more likely to carry higher amounts of the toxin. However it is not easy to tell from the appearance of the fish if it contains the toxin.
People affected may show symptoms of numbness of the mouth and the limbs, vomiting, diarrhoea, reversal of sensation of coldness and hotness and pain in the joints and muscles.
The spokesman said that most people affected by ciguatoxin would recover without long-term health effects.
However, if excessive toxin was consumed, the circulatory and nervous systems would be affected.
"The toxin cannot be destroyed by cooking," the spokesman said.
To prevent ciguatera fish poisoning, members of the public should observe the following measures:
* Eat less coral reef fish;
* Eat small amounts 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, skin, intestines and roe of coral reef fish, which usually have a higher concentration of toxin;
* When eating coral reef fish, avoid consuming alcohol, peanuts or beans as they may aggravate ciguatoxin poisoning;
* Seek medical treatment immediately should symptoms of ciguatoxin fish poisoning appear; and
* Coral reef fish should be purchased from reputable and licensed seafood shops. Do not buy the fish when the source is doubtful.