Long-term follow-up of histamine levels in a stored fish meal sample

A shipment of fish meal highly contaminated with histamine caused an epidemic histamine poisoning among harbour workers in Rijeka, Croatia, in 1998. Samples of fish meal were taken, histamine level determined, and samples were then stored in closed plastic bags at 4–8 °C for the next 40 months. Follow-up of the histamine levels was performed by thin-layer chromatography (TLC) after 12, 28 and 40 months of storage. Initial histamine level was 5.1 g of histamine in a kilogram of fish meal (100%). After 12 months histamine level decreased to 73.5% (3.75 g/kg), remained at 71.6% after 28 months (3.65 g/kg), and decreased again after 40 months of storage to 49.0% (2.5 g/kg). After 40 months of storage in a refrigerator, samples were kept at the room temperature (24 °C) in the closed transparent plastic bags, exposed to natural daily light for additional 3 months. TLC histamine measurements were performed at days 1 and 7, and then after 1, 2 and 3 months of storage. Levels of histamine did not differ significantly from the starting level of 2.5 g/kg (100%) at days 1 and 7, and also after 1, 2, and 3 months of storage at 24 °C (2.5, 2.3, 2.2, 2.2, 2.2 g/kg, respectively).This study confirmed the long-term persistence of histamine in contaminated fish meal. Histamine was present at the highly toxic level (>2 g/kg) for more than 3 years if stored at 4–8 °C, and for at least 3 months if kept at ambient temperature (24 °C) unprotected from light. The results confirmed our previous hypothesis that fish meal with high content of histamine is a potential long-term health hazard for poultry and other animals if used as a feedstuff and also for men manipulating it.