Neurology of ciguatera

Abstract

Ciguatera is a widespread ichthyosarcotoxaemia with dramatic and clinically important neurological features. This severe form of fish poisoning may present with either acute or chronic intoxication syndromes and constitutes a global health problem. Ciguatera poisoning is little known in temperate countries as a potentially global problem associated with human ingestion of large carnivorous fish that harbour the bioaccumulated ciguatoxins of the photosynthetic dinoflagellate Gambierdiscus toxicus. This neurotoxin is stored in the viscera of fish that have eaten the dinoflagellate and concentrated it upwards throughout the food chain towards progressively larger species, including humans. Ciguatoxin accumulates in all fish tissues, especially the liver and viscera, of "at risk" species. Both Pacific (P-CTX-1) and Caribbean (C-CTX-1) ciguatoxins are heat stable polyether toxins and pose a health risk at concentrations above 0.1 ppb. The presenting signs of ciguatera are primarily neurotoxic in more than 80% of cases. Such include the pathognomonic features of postingestion paraesthesiae, dysaesthesiae, and heightened nociperception. Other sensory abnormalities include the subjective features of metallic taste, pruritus, arthralgia, myalgia, and dental pain. Cerebellar dysfunction, sometimes diphasic, and weakness due to both neuropathy and polymyositis may be encountered. Autonomic dysfunction leads to hypotension, bradycardia, and hypersalivation in severe cases. Ciguatoxins are potent, lipophilic sodium channel activator toxins which bind to the voltage sensitive (site 5) sodium channel on the cell membranes of all excitable tissues. Treatment depends on early diagnosis and the early administration of intravenous mannitol. The early identification of the neurological features in sentinel patients has the potential to reduce the number of secondary cases in cluster outbreaks.

Ciguatera fish Poisoning: a Challenge to Emergency Physicians

“…1,2,8,13 The acute illness lasts a mean of eight days but severe neurological manifestations can last for months and even years in 5% of patients. 1,2,5,8 Severe chronic fatigue and weakness occur in 3-20% of patients and can also result in depression and insomnia in some of the victims. 2 The severity depends on the amount and the part of fish ingested.…”

“…1,2,4,7 This neurotoxin is stored in the viscera of fish that have eaten the dinoflagella and subsequently concentrated upwards in the food chain towards larger fishes, and human is the last host in the food chain. It accumulates in all tissues but particularly in the head, roe, liver and other viscera.…”

“…1,2,5,8 Severe chronic fatigue and weakness occur in 3-20% of patients and can also result in depression and insomnia in some of the victims. 2 The severity depends on the amount and the part of fish ingested. More toxins concentrate in the head, roe, liver and viscera.…”

“…1,2,9 Although harmless in fish, the toxin produces illness in humans by interrupting the calcium regulation of cell membrane sodium ion channels, principally in nerve and muscle tissues causing water influx and nodal swelling. 1,2,10,11 Most of the ciguateric fish found in Hong Kong come from coral reef area (Table 2). 12 One cannot readily tell from the appearance of the fish if it contains the toxin.…”

“…It has been reported in the United States, Madagascar, Europe, the South Pacific and Hong Kong. 1,2 The patients may present with a mixture of gastrointestinal, neurocutaneous and constitutional symptoms. It also occurs commonly in Hong Kong as epidemic outbreaks.…”