| No: 13 | January 2008 |
“Between 2006 April 12 and 19, two suspect cases of Scombroid poisoning were reported to Vancouver Coastal Health following consumption of lightly cooked (seared) tuna called AHI and YELLOWFISH by the distributor. The cases were contracted from meals in two unrelated restaurants in the Vancouver area. We have been advised that the implicated lots of tuna were also distributed in the Calgary Health Region, specifically to Calgary and Airdrie Superstores. These lots have been recalled by the CFIA, and Calgary Health Region Public Health Inspectors are monitoring stores for completeness of the recall. Cases could present to Emergency Departments or Urgent Care Centres in the next few weeks if the tuna was frozen before use in the home.” SCOMBROTOXIN Toxin produced by the growth of certain bacteria and the subsequent action of their decarboxylase enzymes on histidine and other amino acids in food.
SCOMBROID POISONING Scombroid Poisoning, also called Histamine Poisoning, is caused by the ingestion of foods that contain high levels of histamine and possibly other vasoactive amines and compounds. Histamine and other amines are formed by the growth of certain bacteria and the subsequent action of their decarboxylase enzymes on histidine and other amino acids in food, either during the production of a product such as Swiss cheese or by spoilage of foods such as fishery products, particularly tuna or mahi mahi. However, any food that contains the appropriate amino acids and is subjected to certain bacterial contamination and growth may lead to scombroid poisoning when ingested. While histamine poisoning is well known and is by far the most important form, a range of different related toxins, known as biogenic amines, can cause disease. However, the actual nature of the toxin(s) is controversial. Biogenic Amine Production and It's Control Many types of bacteria are capable of producing the biogenic amines regarded as causing histamine poisoning. Also, the enzymes responsible (decarboxylases), once produced, may still be active even if the bacteria that produced them are subsequently controlled. Control of biogenic amine production is best summarised by food type. Fish: Histamine food poisoning is most often associated with a particular group of fish, including the scombroid fish, that have high free levels of the amino acid histidine (i.e. not contained in proteins) in their flesh. Scombroid fish can have a 14 day safe shelf life at 0oC if chilled quickly (meaning reducing the internal temperature to 10oC or less in 6 hours), but this reduces to only 7 days at 4.4oC (these times include time on the boat). The fish should not be exposed to Cheese: Biogenic amines are produced during ripening as the casein is slowly degraded by Meat: Amines can accumulate during the production of fermented meat products. Foods such as salamis should be made from good quality raw ingredients. Frozen ingredients of suitable quality can be thawed at 5oC for 3 days when a starter culture is used. Short fermentations and the use of appropriate starter cultures used under optimum conditions assist in reducing amine formation (possibly by the rapid decrease in pH that results). Fermented Vegetables: Hygienic practice and the use of starter cultures with low decarboxylase activity assist in the prevention of amine formation. Nature of Disease Incubation: Ranges from several minutes to several hours. Mean incubation period around 1 hour. Duration: Normally lasts for a few hours but can last for days. Symptoms: Histamine. May include rash, localised skin inflammation, nausea, vomiting, diarrhoea, abdominal cramps, low blood pressure, headache, tingling, flushing and severe respiratory distress. The most consistent sign is a flushing of the face and neck causing heat and discomfort, which can appear similar to sunburn. Tyramine. This acts indirectly to increase blood pressure by narrowing peripheral blood vessels and increasing the output from the heart. Other symptoms include dilation of the pupils, swelling of the eyes and tear production, salivation, increased respiration and blood sugar concentration. Toxins: The actual nature of the toxin is the subject of much debate, at least in fish. The biological effects of histamine are reported to be increased in the presence of other spoilage products, as fish containing a level of histamine seem to be more toxic than the same amount of histamine administered orally by itself. Another theory suggests that an unknown toxin from
spoiled fish actually mediates the release of histamine from the body's cells. Whatever the actual toxin(s) involved, biogenic amines in food are at least indicators of the presence of these toxin(s). Long Term Effects: Rarely, cardiac and respiratory complications occur. Dose: The situation regarding a toxic dose is unclear (not least because the chemical(s) responsible is not known). Approximately 100 mg/100g histamine is considered to be toxic, but a number of incidents have involved foods containing less than 5 mg/100g histamine. A limit commonly used is 30 mg/100g, although the FDA have a limit of 50mg/100g. For tyramine a toxic dose of 10-80 mg has been suggested. Treatment: Administration of antihistamines for histamine poisoning. between consuming this sort of food and disease. Associated Foods Fishery products that have been implicated in scombroid poisoning include the tunas (e.g., skipjack and yellowfin), mahi mahi, bluefish, sardines, mackerel, amberjack, and abalone. Many other products also have caused the toxic effects. The primary cheese involved in intoxications has been Swiss cheese. The toxin forms in a food when certain bacteria are present and time and temperature permit their growth. Distribution of the toxin within an individual fish fillet or between cans in a case lot can be uneven, with some sections of a product causing illnesses and others not. Risk populations All humans are susceptible to scombroid poisoning; however, the symptoms can be severe for the elderly and for those taking medications such as isoniazid. Because of the worldwide network for harvesting, processing, and distributing fishery products, the impact of the problem is not limited to specific geographical areas or consumption pattern. Prevention Neither cooking, canning, or freezing reduces the toxic effect. Common sensory examination by the consumer cannot ensure the absence or presence of the toxin. Chemical testing is the only reliable test for evaluation of a product. Therefore all non-fresh or improperly preserved fish products may contain histamine or related products. Fortunately, production of histamine often, but not always, correlates with the production of ammonia, resulting in a clear spoiled or off-smell. References http://www.food-info.net/uk/tox/scombro.htm Case information from;
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