At least three people have been treated in hospital for scombroid poisoning after eating Trevally from a meal kit supplied by Hello Fresh.
Histidine in the fish tissue can be converted to histamine by histidine decarboxylase, found in Escherichia coli, Morganella morganii, Proteus, Pseudomonas and Klebsiella species, which may occur naturally in the gills, skin and gut. If the fish is not properly handled after being caught and during transport and distribution, allowing the temperature to rise for an extended period, these bacteria can grow and produce sufficient histamine to cause an allergic reaction in the consumer.
Scombroid poisoning was originally named because Scombridae fish naturally contain higher levels of histidine. The range of symptoms varies, but includes nausea, headaches, vomiting and diarrhoea and possibly itching and a burning sensation in the lips.
Unfortunately, the fish may not appear to be spoiled and the enzyme remains active even after the bacteria have been killed, continuing to produce histamine under cold storage. Activity can resume when frozen fish is thawed. Histamine cannot be destroyed by cooking, so control of storage temperature is essential throughout the food chain.