Fish Microbiology and Quality Assurance

6.4.4. Scombroid poisoning
Scombroid poisoning or histamine poisoning is caused by the consumption of fishes containing high levels of histamine. Scombroid fishes (tuna, seer fishes, mackerel) containing red meat are implicated in scromboid pisoning. Other fishes like carangids, herrings, sardines and anchovies are also involved in histamine poisoning.
Source of histamine
Scombroid fishes have high levels of histidine which is converted to histamine by the growth of microorganisms pocessing the enzyme histidine decarboxylase. Conversion of histidine to histamine by microorganisms results in the accumulation of histamine in fish.
Bacteria involved in decorboxylation are Morganella morgani, Klebsiella pnemoniae, Enterobacter aerogenes and Haffnia alvei. The main source of these bacteria to fish is from post harvest contamination. Though these bacteria grow well at 10^oC, highest histamine production occurs at 37^oc. Histamine is heat resistant.
Symptoms

• Symptoms of poisoning occur with short incubation period (few minutes to few hours), the illness is mild and self limiting lasting for only few hours.
• Gastrointestinal disturbance (nausea, vomiting, diarrhea), facial flushing, labial edema, itching of the skin and rashes on skin are the common symptoms of illness.
• Maximum permissible limit in seafood is 50 ppm.