MEDLINE 1966 to October 2004 and EMBASE 1980 to October 2004 were searched for: “marine poisoning”, “nerve conduction studies”, “neurotoxicity”, “ciguatera”, “tetrodotoxin poisoning”, and “shellfish poisoning”. Further articles were included from reference lists, review articles, and major textbook chapters on marine toxinology. Abstracts and reports from meetings were also included. The final reference list was generated based on originality and relevance to the topics covered in the
ReviewNeurotoxic marine poisoning
Section snippets
Marine poisoning
An important distinction between envenoming and poisoning is pertinent to marine poisoning. Venomous animals have a specialised gland that produces venom, and the venom is applied or injected parenterally. Other marine animals accumulate toxic compounds from their environment and do not have specialised toxin-producing glands; consequently, these animals must be ingested to produce toxic effects.6 Marine poisons generally consist of heat and gastric-acid stable low-molecular-weight toxins.6
Impulse conduction
In peripheral-nerve myelinated axons, voltage-sensitive Na+ channels in the nodal axon are clustered at high densities (up to 1000/μm2) compared with the internodal region (25/μm2).7 The high density of Na+ channels at the node reflects the need of saltatory conduction for a large inward current at the node (figure 1).8 When the nodal membrane is depolarised, an inward current forms, carried by Na+. The Na+ conductance is voltage sensitive and regenerative: it increases with depolarisation, and
Ciguatera poisoning
The commonest marine poisoning, ciguatera is endemic throughout subtropical and tropical regions of the Indo-Pacific and Caribbean.12, 13, 14, 15, 16, 17, 18, 19, 20 Ciguatera is rarely fatal and causes moderate neurological and gastrointestinal effects in most people. With the transportation of fish to distant locations, ciguatera is now also being reported in non-endemic regions.6
Ciguatera is caused by the ingestion of ciguatoxins that accumulate in certain tropical and subtropical finfish.13
Puffer fish (tetrodotoxin) poisoning
Puffer fish poisoning results from the ingestion of fish containing tetrodotoxin and is the commonest lethal marine poisoning. Tetrodotoxin poisoning mainly occurs in southeast Asia, most commonly in Japan where fugu (puffer fish fillet) is a delicacy.50, 51, 52, 53 In the early part of the 20th century, 100 deaths per year from ingestion of fugu were reported in Japan;52 the rate of deaths has decreased substantially with improved legislation of fugu preparation and marketing. However,
Shellfish poisoning
Shellfish contamination is a medical and economic problem affecting fisheries mainly in temperate regions. Although viral and bacterial infections resulting from shellfish ingestion are more common, toxin-mediated shellfish poisoning can cause severe and life-threatening neurological effects. Toxic shellfish poisoning makes up about 1·1% of food-borne illness, or 7·4% of marine intoxications in the USA.6
Four major toxic syndromes result from shellfish ingestion and three of these are mostly
Other neurotoxic marine poisoning
Clupeotoxism is an enigmatic marine poisoning reported from the Caribbean and Indo-Pacific region that results from the ingestion of plankton-eating fish, such as herring and sardines.6, 73, 95 The effects of clupeotoxism are more severe than for other marine poisoning and the fatality rate is high.95 Gastrointestinal symptoms include nausea, vomiting, abdominal cramping, and diarrhoea associated with an unusual sharp metallic taste. Neurological effects include dilated pupils, paraesthesia,
Conclusion
Description of the common neurotoxic marine poisonings is important for increased awareness of these syndromes. However, prevention of potentially life-threatening poisoning is key and clearly, people should exercise caution—discretion rather than valour—whenever confronted with a plate of exotic shellfish or large tropical fish. Travellers should consult appropriate medical travel-information services for region and season specific information.
Search strategy and selection criteria
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A comparison of the potential role of the tetrodotoxin-insensitive sodium channels, PN3/SNS and NaN/SNS2, in rat models of chronic pain
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Ciguatera fish poisoning: a double-blind randomized trial of mannitol therapy
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Clinical observations on 3009 cases of ciguatera (fish poisoning) in the South Pacific
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Clinical features of 12 890 cases of ciguatera (fish poisoning) in French Polynesia
Ciguatera in Australia: occurrence, clinical features, pathophysiology, and management
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Ciguatera: Caribbean and Indo-Pacific Fish Poisoning
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Fish poisoning in Fiji
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Ciguatera fish poisoning in Miami
JAMA
Ciguatera fish poisoning: epidemiology of the disease on St Thomas, US Virgin Islands
Am J Trop Med Hyg
Risk of ciguatera fish poisoning: impact on recommendations to eat more fish
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Ciguatera and pregnancy
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Pacific ciguatoxin-1 associated with a large common-source outbreak of ciguatera in east Arnhem Land, Australia
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