Scombrotoxic Fish Poisoning Secondary to Tuna Ingestion

Ferris HA1, Ryan FM1, Byrne K2, Fleming E2, O’ Sullivan H2, Hamilton D2

1Department of Public Health Medicine, HSE-South, Cork, Ireland.
2 South Lee Environmental Health Services, HSE- South, Cork, Ireland.


Scombrotoxic poisoning results from the improper handling and refrigeration of fish containing naturally occurring histidine. Scombroid fish species such as tuna, mackerel and swordfish contain histidine, which is converted to histamine when inadequately chilled. European legislation states that scombroid fish species should be tested for the presence of histamine and mean values should be <100mg/kg1. The authors report an outbreak of scombrotoxic fish poisoning in 12 individuals following ingestion of tuna. Symptoms occurred rapidly and included flushing, headache, palpitations and diarrhoea. Fortunately, symptoms were short lived and self-limiting except in one individual, who required anti-histamine medication. Adequate refrigeration practices are crucial in preventing scombrotoxic food poisoning.

Scombrotoxic poisoning, also known as histamine fish poisoning, is a toxic reaction to decomposing scombroid fish species such as tuna, mackerel or swordfish2. Scombrotoxic poisoning is uncommon with no formal incidence figures available in Ireland. However, in the UK it is estimated that 0-10 cases occur annually3. Scombroid fish naturally contain high levels of histidine, which is converted into histamine by the enzyme histidine decarboxylase when fish is preserved incorrectly and/or improperly refrigerated4. Histamine fish poisoning is a clinical diagnosis based on the characteristic syndrome in close proximity to fish ingestion5. Histamine is heat stable; therefore cooking the fish does not reduce the histamine levels. European legislation [Regulation (EC) 1441/2007] states that scombroid fish species should be tested for the presence of histamine. The mean value of histamine should be <100mg/kg to be safe for human consumption1.

Case Report:
The authors report an outbreak of histamine toxicity secondary to the ingestion of tuna. In August 2017, a fish wholesaler provided tuna to a catering company, which was operating under a catering contract to a private company. Twenty-one individuals ate tuna and 12 individuals promptly became ill after ingestion. Onset of symptoms ranged from 0 to 2.5 hours post ingestion. The attack rate was 57% i.e. the proportion of ill persons among those exposed. No other food items were associated with illness. Symptoms reported included flushing, increased heart rate, sweating, headache, abdominal cramps and diarrhoea. Symptoms were short lived and self-limiting in 11 out of 12 cases. One individual attended a General Practitioner and required anti-histamine medication.

Environmental Health Officers performed a site inspection of the premises from which the tuna was served and were satisfied with the temperature control, hygiene standards and record keeping of the business. The use of an electronic cashless system by both the catering and host company provided real time information on food purchased and provided the catering company with sufficient information to promptly withdraw the tuna from the menu. It also provided the Outbreak Control Team with timely comprehensive information. The Food Safety Authority of Ireland conducted a trace-back investigation of the tuna. Thirty-three samples of leftover tuna were sent to the Public Analyst Laboratory (PAL), Cork and 15 subsamples were tested for histamine. The tuna had been seared when fresh, then frozen and brought to the laboratory. Every sample exceeded the legislative limit of histamine. The average histamine in the entire sample was 1405mg/kg, therefore unsuitable for human consumption.

Temperature control is the crucial step in preventing scombrotoxic fish poisoning. The Food Safety Authority of Ireland and the Irish Sea Fisheries Board highlight the importance of proper handling and chilling of fish from time of catch through to transportation, processing, storage and distribution6,7.

Conflict of interest:
None declared.

HA Ferris, SpR Public Health Medicine, Department of Public Health, Floor 2 Block 8, St Finbar’s Hospital, Cork.
Email[email protected]

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6) Food Safety Authority of Ireland 2011. Information for caterers on microbial toxins and marine biotoxins. Available at file:///C:/Users/helena.ferris/Downloads/Microbial%20Toxins%20Factsheet%20FINAL.pdf
7) Irish Sea Fisheries Board. Histamine in Seafood. Available at,in,Seafoods.pdf