Clinical Symptoms

People usually remember that the offending fish had a peppery taste. After ingestion or within 2 h, the patient shows several gastrointestinal effects, such as nausea,

vomiting, and diarrhea, as well as epigastric distress, headache, and burning sensation of the throat. This can be followed by neurological numbness, tingling, cutaneous flushing, and urticaria. Symptoms subside in ca. 16 h and generally there are no lasting ill effects. Diagnosis of the illness is usually based on the patient's symptoms, time of onset, and the effect of treatment with antihistamine medication. The onset of intoxication symptoms is rapid, ranging from immediate to 30 min. The duration of the illness is usually 3 h, but may last several days. To confirm a diagnosis, the suspected food must be analyzed within a few hours for elevated levels of histamine.


Species of dinoflagellates, particularly Gonylaux sp., produce a toxin that accumulates in clams, mussels, and other shellfish that fed on the algae. The phenomenon of red tides or blooms can occur, resulting in rapid growth of the dinoflagellates. The danger of red tides was well known by the North American West Coast Indians, who refrained from eating shellfish during the first signs of colored water. The toxin has no ill effects on the shellfish, but can be dangerous to humans. Eating such fish can be a serious threat to public health and has been known as paralytic shellfish poisoning (PSP). PSP occurs throughout the world, particular at regions 30° or higher in latitude. The toxin cannot be removed by washing or destroyed by heating. All shellfishes (filter-feeding molluscs) are potentially toxic. However, PSP is generally associated with mussels, clams, cockles, and scallops.

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