The United Nations’ FAO and the World Health Organization have found that the risk of histamine development in fish of the Salmonidae family is unlikely to reach the levels needed to cause food poisoning.

The Food and Agriculture Organization (FAO) of the United Nations and World Health Organization (WHO) said that under appropriate time-temperature control and within sensory shelf-life of the product, scombrotoxin fish poisoning (SFP) is improbable. Fish in the Salmonidae include salmon, trout, chars, freshwater whitefishes, and graylings, which collectively are known as the salmonids.

The Codex Committee on Food Hygiene requested FAO and WHO provide scientific information to consider whether salmonids should be included in new international guidance being developed for the control of histamine in fish and fishery products.

Norway, Chile, the United States and Russian Federation are the largest producers of salmonids. Main importers are China, the United States, Japan, Russia and European unio countries such as Sweden, Denmark, Germany and Poland.

Histamine development occurs when bacteria convert the amino acid histidine in food to histamine. Poisoning happens within a few minutes to several hours after ingestion of foods that contain high levels of histamine.

It is also referred to as SFP because the illness is often associated with consumption of spoiled scombroid fish. Histamine can also be found in fermented foods such as cheeses, salami, fermented vegetables, wine and beer.

Histamine poisoning can cause gastrointestinal symptoms including cramps, diarrhea, vomiting; cardiovascular symptoms including flushing, rash, headache; and neurological symptoms such as pain and itching. Symptoms may last for several days but there is no known long-term impact and patients rarely die.

Compared with scombroid fish which have free histidine levels ranging from 5,000 mg/kg to 20,000 mg/kg, most species in the Salmonidae family have less than 1,000 mg/kg histidine.

The FAO and WHO literature review found evidence that under certain conditions development of histamine can occur in at least two species of the Salmonidae family – Atlantic salmon and rainbow trout. This was based on inoculation studies under laboratory controlled conditions.

“The available evidence indicates that whilst histamine can develop, in many trials it was not detected, or if it was, only in relatively low concentrations, well below current Codex limits set for other species such as tuna, and if at all towards the end or beyond limits of sensory acceptability. In only one of the 21 shelf-life studies reviewed was the Codex limit of 200 mg/kg exceeded, and then only after two weeks of storage after the detection of sensory spoilage.”

Two market level surveys in Iran and Lithuania found that 12.5 percent and 16 percent, respectively, of Salmonidae sampled had levels of histamine which exceeded regulatory limits.

The review of 51 articles identified 11 confirmed cases of SFP-like syndrome linked to consumption of Salmonidae over 40 years. One involved low levels of histamine with a mean of 1.9 mg/kg and another involved high levels with a mean 434 mg/kg in excess of regulatory limits for tuna.

An additional 46 suspected cases of histamine poisoning from salmon were reported between 1976 and 2015, two in the United States and 42 in the United Kingdom.

While more than 80 percent of global production of Salmonidae enters international trade there have been no reported cases of rejections of consignments, although this could also reflect a low frequency of surveillance, said FAO and WHO.

This is compared to 37 RASFF notifications for histamine in tuna in 2017 and at least 72 cases of histamine-related illness linked to tuna consumption in two European countries.

based on controlled spoilage studies, it appears that histamine concentrations in Salmonidae seem to increase only after excessive storage times at the temperatures seleced and days to weeks past sensory shelf-life. With inoculation studies, histamine concentrations did not increase substantially until after extreme abuse conditions.

FAO and WHO said the low number of confirmed cases in relation to the high volume of production, trade and consumption of Salmonidae suggests the hazard is not a significant threat to human health.

They also found salmon may be used as a common name for species that are not members of the Salmonidae family.

The agencies concluded current evidence suggests there is no basis to include Salmonidae in the same risk category for SFP as other more commonly implicated species.

Meanwhile, the FAO and WHO are scheduled to meet to discuss Ciguatera fish poisoning (CFP)  from Nov. 19-23 in Rome. CFP is one of the most common foodborne illnesses related to seafood consumption, but the true incidence remains unclear. Official estimates suggest 10,000-50,000 people per year suffer from this illness.