Histamine fish poisoning revisited

Histamine (or scombroid) fish poisoning (HFP) is reviewed in a risk-assessm ent framework in an attempt to arrive at an informed characterisation of ri sk. Histamine is the main toxin involved in HFP, but the disease is not unc omplicated histamine poisoning. Although it is generally associated with hi gh levels of histamine (greater than or equal to 50 mg/100 g) in bacteriall y contaminated fish of particular species, the pathogenesis of HFP has not been clearly elucidated. Various hypotheses have been put forward to explai n why histamine consumed in spoiled fish is more toxic than pure histamine taken orally, but none has proved totally satisfactory. Urocanic acid, like histamine, an imidazole compound derived from histidine in spoiling fish, may be the "missing factor" in HFP. cis-Urocanic acid has recently been rec ognised as a mast cell degranulator, and endogenous histamine from mast cel l degranulation may augment the exogenous histamine consumed in spoiled fis h. HFP is a mild disease, but is important in relation to food safety and i nternational trade. Consumers are becoming more demanding, and litigation f ollowing food poisoning incidents is becoming more common. Producers, distr ibutors and restaurants are increasingly held liable for the quality of the products they handle and sell. Many countries have set guidelines for maxi mum permitted levels of histamine in fish. However, histamine concentration s within a spoiled fish are extremely variable, as is the threshold toxic d ose. Until the identity, levels and potency of possible potentiators and/or mast-cell-degranulating factors are elucidated, it is difficult to establi sh regulatory limits for histamine in foods on the basis of potential healt h hazard. Histidine decarboxylating bacteria produce histamine from free hi stidine in spoiling fish. Although some are present in the normal microbial flora of live fish, most seem to be derived from post-catching contaminati on on board fishing vessels, at the processing plant or in the distribution system, or in restaurants or homes. The key to keeping bacterial numbers a nd histamine levels low is the rapid cooling of fish after catching and the maintenance of adequate refrigeration during handling and storage. Despite the huge expansion in trade in recent years, great progress has been made in ensuring the quality and safety of fish products. This is largely the re sult of the introduction of international standards of food hygiene and the application of risk analysis and hazard analysis and critical control poin t (HACCP) principles. (C) 2000 Elsevier Science B.V. All rights reserved.