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SCOMBROID POISONING
Tuna fish, a major source of histidine decarboxylase producing bacteria
Certain bacteria produce the enzyme histidine decarboxylase during growth. This enzyme breaks down free histidine, a naturally occurring chemical that is present in larger quantities in some fish (Scombridae) than in others. This results in the formation of histamine and other amines.
The fish are non-toxic when caught, but develops increase in histamine content (Scombrotoxin) with decomposition as bacterial numbers increase. They may look and smell normal, and cooking does not destroy the histamine. Although the condition is caused by histamine intoxication, its pathogenesis is not fully understood, and other toxins or potentiators like tyramine may be involved.
Scombroid fish poisoning is frequently encountered if dead fish remain in set nets during warm sea temperatures, the fish is improperly refrigerated or when refrigeration is delayed.
Scombroid Poisoning can be a result of fluctuating temperatures or even long term high or low temperature spoilage.
Once the enzyme histidine decarboxylase is formed, it can continue to produce histamine in the fish even if the bacteria are not active!
The enzyme can also be active at refrigeration temperatures and is likely to remain stable while the fish is frozen and may be reactivated very rapidly after thawing.
Freezing may inactivate the enzyme-forming bacteria. Cooking can inactivate both the enzyme and bacteria. However, once histamine is formed, it cannot be removed by heat or freezing.
The symptoms of Histamine Food Poisoning (HFP) include:
- Nausea, vomiting, diarrhoea,
- An oral burning sensation or peppery taste in the mouth,
- Hives, itching, red rash (flushing)
- Hypotension (light-headedness, dizziness or fainting).
The onset of the symptoms usually occurs within a few minutes after ingestion of the implicated food (incubation period from 5 minutes to an hour) and the duration of symptom ranges from a few hours to 24 h.
While Scombroid poisoning through the release of Histamines is a specific mixture between a food poisoning and an allergic reaction, other foods can have similar effects and symptoms (as mentioned above)on persons with histamine intolerance. Especially wine and certain cheeses and fruit can lead to this pseudo-allergic reaction. (Pseudo-Allergy: The patient has the severe reaction, but has no specific antibodies IgE (Immunoglobulin) to the food/drink in question.
MOST PHYSICIANS ARE NOT FAMILIAR WITH HISTAMINOSIS AND SCOMBROID POISONING
Studies have shown that histamine-intolerant individuals may have a deficiency of the enzyme, diamine oxidase (extracellular) and/or N-methyltransferase (intracellular), in the small intestinal mucosa, resulting in decreased breakdown, and increased absorption of histamine in the gastrointestinal tract.
Diamine oxidase levels are known to be about 500-fold elevated in pregnancy.
Almost 100 drugs have been shown to inhibit diamine oxidase, including:
- Clauvulanic acid found in Augmentin (antibiotics)
- Doxycyline
- Isoniazid (antibiotics used to treat tuberculosis)
- Metoclopropramide (used to treat 'stomach upsets')
- Verapamil (used to treat heart conditions)
- Promethazine
- Monoamine oxidase inhibitors, MAOI (older drugs used to treat depression)
Zinc, Manganese, Niacin, Vitamin B12 and folic acid may also increase histamine levels.
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