Many pufferfish of the family Tetraodontidae possess a potent neurotoxin, tetrodotoxin (TTX). In marine pufferfish species, toxicity is generally high in the liver and ovary, whereas in brackish water and freshwater species, toxicity is higher in the skin. In 1964, the toxin of the California newt was identified as TTX as well, and since then TTX has been detected in a variety of other organisms. TTX is produced primarily by marine bacteria, and pufferfish accumulate TTX via the food chain that begins with these bacteria. Consequently, pufferfish become non-toxic when they are fed TTX-free diets in an environment in which the invasion of TTX-bearing organisms is completely shut off. Although some researchers claim that the TTX of amphibians is endogenous, we believe that it also has an exogenous origin, i.e., from organisms consumed as food. TTX-bearing animals are equipped with a high tolerance to TTX, and thus retain or accumulate TTX possibly as a biologic defense substance. There have been many cases of human intoxication due to the ingestion of TTX-bearing pufferfish, mainly in Japan, China, and Taiwan, and several victims have died. Several cases of TTX intoxication due to the ingestion of small gastropods, including some lethal cases, were recently reported in China and Taiwan, revealing a serious public health issue.

On November 16, 1998 a food poisoning incident due to ingestion of roe of Takifugu oblongus occurred in Bangladesh, affecting 8 people inclusive of 5 deaths. Their symptoms resembled those caused by tetrodotoxin (TTX) or paralytic shellfish poison (PSP). Immediately after the incident, twenty-two specimens of T. oblongus were collected from the seashore adjacent to the concerned poisoning area and their anatomical distribution of toxicity was determined. They showed a high level of toxicity in the ovary (24.5-323.8 MU/g), though the toxicity levels of the other tissues, skin, muscle, liver, testis, and the viscera (except liver), were relatively low (<2-21.3 MU/g). In contrast, a total of 336 specimens of three marine puffers, T. oblongus, Lagocephalus wheeleri and L. lunaris, which were collected on a regular sampling basis from Bangladesh, showed very low toxicity of less than 10 MU/g in all or most tissues including gonad. The toxin partially purified from the T. oblongus specimens, as well as from the other two species, was indistinguishable from TTX in HPLC analysis. From this result and the symptoms of the victims, the causative agent in the above incident was assumed to be TTX.