1st Issue 2005
Prevention and Control of Ciguatera Fish Poisoning

Ciguatera fish poisoning is reported in Hong Kong from time to time, sometimes as large outbreaks. It is caused by the presence in the fish of toxins elaborated by the dinoflagellate that grows in coral reef areas. Fish eating the algae accumulates the toxins, and the effect is magnified through the food chain so that large predatory fish become the most toxic. This occurs worldwide in tropical areas.

While the ciguatoxin does not cause the marine fish any harm, human may suffer numbness of extremities and around the mouth, vomiting, diarrhea, muscle and joint aches several hours after consumption of ciguateric fish. If the fish consumed contains a high concentration of the toxin, the nervous and circulatory systems will be adversely affected. Most cases of ciguatera fish poisoning are self-limiting. The toxin cannot be removed by cooking or refrigeration.

Ciguateric fish

Ciguateric fish cannot be identified by appearance, taste, texture or smell. Quick and reliable screening tests for ciguateric fish are not yet available. In general, the larger the fish, the more likely and the higher the concentration of toxin present. Ciguateric fish is found in tropical waters. In Hong Kong, cases of ciguatera fish poisoning had been related to live coral reef fish imported from areas such as the Nan Sha Islands and the South Pacific.

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, Lyretail Grouper, Two-spot Red Snapper, Humphead Wrasse, Tiger Grouper, Flowery Grouper and Spotted Coral Grouper. Sizes of fish involved in reported cases usually ranged from one to five catties, but fish under one catty or over 20 catties had also been reported.

Code of practice

A code of practice (COP) for the prevention and control of ciguatera fish poisoning has been developed for the trade. According to the COP, importers are required to report to the Food and Environmental Hygiene Department (FEHD) the date of arrival, amount, type, size and source of fish within 48 hours of the arrival of every shipment of live coral reef fish. Moreover, importers, wholesalers and retailers are advised not to import, purchase and sell coral reef fish of high risk or from unknown or suspicious sources, and to keep (for at least 60 days from the date of each transaction) proper and accurate records of the supplies and distribution of all live marine fish. The records should be readily available for inspection at all times by public officer(s). The COP became effective on 15 December, 2004.

How to prevent ciguatera poisoning

Copies of the COP on the regulation of the sale of live marine fish have been distributed to importers, wholesalers (including local fish farms) and retailers (including restaurants selling live marine fish) who import or sell live marine fish. To further reduce the risk of ciguatera poisoning, attention should be paid to the following:

Colouring Matters in Food under a Magnifying Glass

The Chinese have always been particular about eating, paying much attention to the colour, aroma and flavour of food. In the course of food production, food manufacturers may add colouring matters into the food so as to restore their colours or make them look more appealing. Colouring matters are food additives that are natural or synthetic. It is difficult to tell just from the appearance of the food.

Natural colouring matters come from natural ingredients. For example, juice may be extracted from flowers, fruits, stems and roots of plants, dehydrated and grinded into powder to be used as colouring matters. Natural colouring matters are relatively unstable and have low dyeing ability. More is required in the colouring process and hence leading to higher costs. Synthetic colouring matters are artificially synthesized. They come in brighter colours and are more stable, so the colours are better preserved in food processing. Owing to their high dyeing ability, the quantity required is relatively small.

As the public is concerned about the safety of synthetic colouring matters, many countries have drawn up stringent measures to control those used for human consumption. Both natural and synthetic colouring matters can be safely consumed so long as they are properly applied to food.

Cases detected under the Food Surveillance Programme

Under FEHD's regular food surveillance programme, samples of different food products are taken from the market for analysis. Orange II, a colouring matter not permitted under the Colouring Matter in Food Regulations, was found in Chinese puddings. The pudding manufacturers and vendors concerned were both prosecuted and convicted. During the follow-up investigations, testing results of samples of the same kind of food taken from the market were satisfactory.

In response to earlier reports of the suspected use of colouring matters in purple sweet potatoes and yellow croakers sold on the market, FEHD had conducted special inspections to various retail outlets including market stalls throughout the territory and had taken samples for laboratory analysis. Laboratory results revealed that all samples of purple sweet potatoes contained a purple pigment called anthocyanin.

Anthocyanin is a natural colouring matter found in many edible fruits and vegetables such as purple sweet potatoes, grapes, red cabbages and berries, and are generally innocuous for human consumption. Colour seepage that occurs when a purple sweet potato is cut open is a natural phenomenon commonly found in vegetables and fruits.

As for yellow croakers, among the samples taken for analysis, two obtained from the same retailer were found to contain Tartrazine and Sunset Yellow FCF. While these two colouring matters are permitted under the Colouring Matter in Food Regulations to be added to food, it is prohibited by law to add colouring matters to fresh fish in a raw and unprocessed state. Offenders shall be liable to a fine of $ 50,000 and six-month imprisonment.

According to the Colouring Matter in Food Regulations, citrus fruit may have in or upon it added permitted colouring matter if:

  1. the words "colour added" are marked on the skin of such fruit in permitted colouring matter; and
  2. such words are clear and legible, and of such size as to be conspicuously visible.

Notes on Food Purchase

Consumers should pay attention to the following:

For food complaints, please approach the District Environmental Hygiene Offices of FEHD or call the 24-hour hotline on 2868 0000.

News in Brief: The Communication Resource Unit Certified with ISO 9001:2000

To enhance the service standard of an organization, one essential feature is a quality management system. Developed by the International Organization for Standardization (ISO), the ISO 9001:2000 quality management system standards helps to establish, record and maintain a quality management system. It also demonstrates the commitment of an enterprise to quality assurance and its ability to satisfy clients' needs.

To keep abreast of the times, the Communication Resource Unit of FEHD has adopted the ISO 9001:2000 quality management system and, having been audited by an international certification body, was certified with ISO 9001:2000 on 31 January 2005.

The Communication Resource Unit will strive for continual improvements to provide better services to the public.

Trilingual Telephone Hotline System

FEHD's Trilingual Telephone Hotline System has been in service. The public can call the departmental hotline on 2868 0000 to listen to information on food safety and environmental hygiene in Cantonese, Putonghua and English by following the recorded instructions.

The Trilingual Telephone Hotline System disseminates information on food updates, food safety, food poisoning, gastro-intestinal diseases, mosquito prevention and environmental hygiene. Amusing dramas based on such information are available. Callers can obtain fax transmission of the information required. For further details on the Trilingual Hotline System, please visit FEHD's webpage at: http://www.fedh.gov.hk/events/talk/20050110_hotline_index.htm

The Assurance of Food Safety--Harmful Substances in Food Regulations

The Public Health and Municipal Services Ordinance (Cap 132, Laws of Hong Kong) stipulates that food for sale in Hong Kong must be fit for human consumption. Its subsidiary legislation, the Harmful Substances in Food Regulations, listed 39 harmful substances, together with their maximum concentration, allowed in specified foods. Alfatoxin is among one of them.

The maximum concentration of aflatoxin allowed in any food (other than peanut or its products) is 15 micrograms per kilogram of the food, and that in peanuts or peanut products is 20 micrograms per kilogram of the food.

The Regulations also stipulate that no person shall import, consign, deliver, manufacture or sell, for human consumption, any food of a description specified in the regulations which contains harmful substances in greater concentration than is specified thereto. Any person who contravenes the regulations is liable on conviction to a maximum fine of $50,000 and to imprisonment for six months.

The Harmful Substances in Food Regulations also contain a list of seven prohibited substances, namely dienoestrol (including salts and esters thereof), diethylstilboestrol (including salts and esters thereof), hexoestrol (including salts and esters thereof), avoparcin, clenbuterol, chloramphenicol and salbutamol.

Take, for example, clenbuterol. Consumption of clenbuterol tainted pig offal and pork may cause symptoms like dizziness, headache, hand tremor, palpitation and agitation.

Under the regulations, no person shall import, sell, consign or deliver for human consumption any fish, meat or milk which contains any substance specified thereto. Any person who contravenes the regulations is liable on conviction to a maximum fine of $50,000 and to imprisonment for six months.

Advice to consumers