From May 1976 to October 1978, 17 incidents of food poisoning involving 125 persons occurred in the Kyushu district. An epidemiological survey, showed that all the patients had eaten raw flesh (arai) and soup (koikoku) of the carp (Cypriniformes cyprinus). They exhibited symptoms of the nervous system, for example vomiting, convulsion, numbness, speech impediment and difficulty in rising and walking.
All the carp involved appeared fresh and normal, and there was no evidence of microbial contamination.
When the carp flesh that had caused the food poisoning, or hot-ethanol extracts of it, were administered to two dogs, they showed the same symptoms as humans. These symptoms were also observed in monkeys and cats on either oral or intraperitoneal administration. However, mice were less sensitive to the poison.
These findings indicated that the carp flesh contained a hot-ethanol-soluble toxic substance. When the crude extracts were subjected to thin layer chromatography after clean-up, the toxic substance could be detected as a distinct blue-green spot on the plate by spraying 20% sulfuric acid, then charring. Using both the blue-green spot and the toxicity as markers, the crude substance was purified by simple liquid-liquid partition, column chromatography and preparative thin layer chromatography.
The purified substance showed one spot on a thin layer chromatographic plate. Physical data were: m/e 575 (parent mass peak) and UV λ^EtOH_max, 220nm and 282nm. Studies are in progress to determine further properties and to identify this substance.