Poisoning by shellfish and fish results from infection with ptomaines developed by micro-organisms, as in cases of milk and meat poisoning. In addition, it must be remembered that there are a number of persons who, from idiosyncrasy, possess an extreme degree of sensitiveness to the action of shellfish of all kinds. To such persons the eating of clam broth or raw oysters, crabs or lobsters, may give rise to violent outbreaks of urticaria or eczema, or produce severe headache, nausea, and vomiting. It is scarcely probable that these cases are due to the same source as those of true ptomaine poisoning, for they occur when the shellfish have been eaten in perfectly fresh condition; the symptoms, moreover, are usually less violent than those caused by ptomaines, and similar effects are produced in some people by certain vegetables and fruits, like the strawberry. Among shellfish the mussel furnishes the most violent poison. This substance Brieger has isolated under the name of "mytilotoxin." It develops particularly in the liver of the animal. The intensity of the poison depends somewhat upon the locality in which the animal has lived and fed. The same mussels may become non-toxic in different waters.

The name ichthysmus is applied to fish poisoning in general, osteotoxismus to oyster poisoning.

Symptoms

The symptoms of poisoning from eating raw fish or cooked mussels in which ptomaines have developed are somewhat different from those of meat and milk poisoning in that they concern the nervous system with less gastro-intestinal disorder. For this reason the poison is very much more dangerous, and cases have been known to result fatally two hours after eating mussels. In such instances there may be no nausea, vomiting, or fever, but there is sudden and extreme prostration, with numbness, faintness, coldness of surface, dilatation of the pupils, double vision, restlessness, nervousness, anxiety, and a feeble and very rapid pulse. In France hard-roed herrings have caused such symptoms. Decomposing oysters and fish may also produce symptoms of gastro-intestinal poisoning resembling those from the use of bad meat. The salted sturgeon which is eaten extensively as a food in parts of Russia has caused death from its decomposition, and a variety of fishes both in European and Eastern waters are capable of developing very active toxins. In Russia poisoning has been produced by eating the ova of the pike, barbel, and perch, and decomposed sturgeon roe (caviare). Portions of the porpoise, eaten in China, may prove poisonous unless thoroughly boiled.

The mackerel family has three species which are poisonous, namely the jurel, bonito, and chicaro. They are found in the West Indies. Two species of herring are poisonous; one of them, the meletta, taken along the Atlantic coast from Florida to New York, has caused several fatal cases of poisoning.

Georgii reported in 1901 the poisoning of 24 men from eating a salad of canned lobster. The symptoms resembled fish poisoning. Urticaria was absent, but in one case there was glycosuria.