First signs in the Bischoffs' fatal meal emerge
PRELIMINARY tests attributed the tragic deaths of Sunshine Coast woman Noelene Bischoff and her daughter, Yvana, in Bali last month to scombroid fish poisoning, in combination with their asthma.
Scombroid poisoning arises from the consumption of fish that contain a high level of histamine, a chemical normally produced in response to an allergen.
Not surprisingly, the symptoms generated are often mistaken for an allergic reaction to the fish itself.
High levels of histamine are generated in the flesh of the fish due to bacterial contamination, usually from poor storage and particularly from inadequate refrigeration.
These conditions allow bacteria to proliferate and convert an amino acid called histidine, naturally present in the flesh of the fish, into histamine.
Usually the symptoms are mild and dissipate without treatment in eight to 12 hours. But in people who are more susceptible, or who have consumed fish containing particularly high levels of histamine, the symptoms can be severe.
People with asthma and other allergic conditions may be severely affected.
Symptoms include burning and tingling of the lips and mouth, sweating, vomiting and diarrhoea, headaches, blurred vision, palpitations and dizziness.
In severe cases, and particularly in victims suffering from asthma, the muscles of the bronchi may contract and narrow, obstructing the respiratory airway and making it difficult to breath.
Symptoms can develop within a few minutes of eating the contaminated fish, but in some cases may be delayed.
The condition is called scombroid poisoning because it is often associated with fish of the family scombridae. That includes tuna, herring, mahi-mahi (dolphinfish), mackerel, sardine, anchovy, skipjack and about 100 other species that tend to have a naturally high level of histidine in their flesh.
In Australia, 57 people reportedly contracted combroid poisoning between January 2009 and December 2013. Nine were hospitalised, but no deaths reported.
However, it is more common in South-East Asia, where scombroid species are more prevalent, and in regions where storage and refrigeration facilities are less than adequate.
If the condition is recognised, and the symptoms are severe, it can be readily treated with oral antihistamines. This usually resolves the symptoms within 15 to 30 minutes.
It is often not possible to tell by observation whether a fish has a high histamine level, but sometimes contaminated fish has an unusual odour - reminiscent of ammonia - or a metallic, sharp, salty or peppery taste.
Sometimes, when cooked, the flesh of fish that are high in histamine has a honey-combed appearance.
Prevention is better than cure, so it is wise to ensure, wherever possible, that any fish you consume is fresh or has been frozen immediately after being caught.
When travelling to countries where storage conditions may be suspect, it is worth having oral antihistamines at hand.
* Bob Mead is chair of the Forensic Biology and Toxicology program at Murdoch University.