Ciguatera:
Worldwide, ciguatera fish poisoning is the most common of the clinical syndromes associated with marine biotoxins. It is a major public health problem in the Caribbean and South Pacific regions, particularly in areas with tropical reefs.[8-10] Illness is caused by toxins (ciguatoxins, and others) that are passed up the marine food chain; large predatory reef fish (e.g., barracuda, jacks) have the greatest risk of being toxic. Toxins are produced by the dinoflagellate Gambierdiscus toxicus, the presence of which has been associated with disruption of normal reef ecology and reef communities.
Gastrointestinal symptoms—nausea, vomiting, and diarrhea—are the first manifestation of illness and usually occur within 24 hours of eating a toxic fish. In severe cases, patients may also be acutely bradycardic and hypotensive and, in rare instances (confined almost exclusively to cases in the Pacific region), may develop respiratory difficulties. The most characteristic symptoms are headache and dysesthesias: tingling sensations in the extremities and around the mouth, cold allodynia (cold objects feeling burning hot), burning sensation in the mouth, and aching pain around the teeth. These symptoms may persist for weeks to months[9-11] and may be linked with clinical depression. The diagnosis is clinical; other than identifying toxin in fish samples that may be left over from an implicated meal, there are no confirmatory tests. Treatment is symptomatic, including maintenance of adequate hydration, use of atropine for bradycardia, and administration of analgesics and antidepressants, as appropriate. Some literature suggests that intravenous mannitol alleviates acute symptoms, although no benefit was seen in one double-blind randomized clinical trial.[12] Anecdotal data suggest that tocainide helps alleviate neurologic symptoms.
Prevention is difficult, as toxic fish have a normal appearance and taste. In endemic areas, this may have major economic and nutritional impact, as local populations are often reluctant to eat locally caught fish because of the risk of ciguatera. Feeding of suspect fish to the family cat to see if symptoms result is a not uncommon practice prior to human consumption in such areas.
Paralytic Shellfish Poisoning:
Paralytic shellfish poisoning is the most common cause of marine biotoxin–associated illness in the continental United States and Alaska.[13] Illness has traditionally been associated with eating clams and mussels that contain saxitoxins produced byAlexandrium spp. and related dinoflagellates, although a variety of other vehicles have been reported.[14] Unlike ciguatera poisoning, gastrointestinal symptoms are less prominent than neurologic manifestations: circumoral paresthesias and paresthesias of the extremities usually appear within 1 hour of ingesting toxic shellfish, and they may be accompanied by ataxia, dysphagia, and changes in mental status. Hypertension may occur and corresponds to the ingested dose, and, in the most severe cases, patients may proceed to respiratory paralysis, usually within the first 24 hours of illness. In experiments, saxitoxins can be identified in serum and urine samples from affected patients.[15] Treatment is symptomatic. Prevention is achieved through regular monitoring of shellfish populations for saxitoxin by public health authorities, with sampling data available on state health department web pages
Neurotoxic Shellfish Poisoning
Illness is caused by brevetoxins produced by Karenia brevis, a major cause of red tides along the Florida coast; otherKarenia species have been implicated in illness in other parts of the world. Ingestion of shellfish containing the toxin causes nausea and vomiting, as well as circumoral paresthesias and paresthesias of the extremities. In more severe cases, patients may report ataxia, slurred speech, dizziness, and, in rare cases, mild respiratory distress.[16] Aerosolization of toxins by heavy wave action on the Atlantic coast of Florida can result in respiratory irritation and asthma-like symptoms in persons walking along affected beaches.[17] On an experimental basis, brevetoxin metabolites have been identified in urine samples from affected patients.[18] Treatment is symptomatic. The Florida Department of Health and other health authorities regularly monitor coastal areas for the presence of K. brevis, and they notify consumers accordingly
Scombroid:
Then patients have this symptom, fish poisoning, shellfish poisoning (Table 99-4), the so-called Chinese restaurant syndrome, and niacin poisoning are some of the major possibilities. Histamine fish poisoning (scombroid) is characterized by symptoms resembling those of a histamine reaction. Burning of the mouth and throat, flushing, headache, and dizziness are common; abdominal cramps, nausea, vomiting, and diarrhea also occur in most cases.[81] In severe cases, urticaria and bronchospasm may also occur. Symptoms are thought to result from histamine. Histamine build-up in fish is caused by a high concentration of histidine in fish flesh being combined with a high concentration of marine bacteria, usually caused by inadequate refrigeration, which catalyze the decarboxylation of histidine to histamine.[82,83] In an outbreak traced to tuna sashimi, a strain of Klebsiella pneumoniae capable of producing large quantities of histamine was implicated.[84] Symptoms usually resolve in a few hours.
