[Paddlewise] Part 2: Ciguatera, Pufferfish and other lovely toxins

Part 2:
Ciguatera fish poisoning. 

  This is a direct consequence of the food chain in tropical and semitropical marine coral reef fish from 35-deg N.to 35-deg S.; excluding plankton feeders, who do not carry the toxin. Ciguatera toxins are produced by Gambeierdiscus toxicus, a toxic dinoflagellate. (Some other dinoflagellates may also play a role in toxin production.) G. toxicus is consumed by herbivorous fish, which in turn are ingested by carnivorous fish.
  As fish in the food chain become larger(or older), more toxin is accumulated, especially in the head, viscera (esp. liver) and roe. Interestingly, the population of toxin-containing fish may be localized, with some reefs toxin-free while other reefs at the same island have inedible toxic fish.
  Pollution seems to increase toxic algae proliferation, including contamination from nuclear testing, industrial wastes, golf course run-off, dumping of ballast water, to name a few.
  Ciguatera poisoning is the most common nonbacterial food poisoning in the U.S., most cases occuring in the Gulf Coast, Virgin Islands and Hawaii. However, the selling of fish to distant buyers has resulted in cases as far north as Toronto and as far inland as Illinois. The problem is even more extensive in the South Pacific.
  Ciguatera toxins are colorless, odorless and tasteless; they are not destroyed by heat, freezing, or stomach acid. However, different cooking methods may change relative concentrations of toxins. Boiling seems to slightly decrease toxicity by removing water-soluble toxins; frying/grilling may increase toxicity of lipid-soluble toxins.
  The most frequently implicated of the 400 or so fishes in Ciguatera poisoning include barracuda, snapper, grouper, or jack, accounting for about 75% of U.S. cases outside of Hawaii, where surgeonfishes and parrot-beaked bottom-feeders are more commonly implicated. Moray eels, trigger-fishes, wrasses, and mullets are also often implicated.
  Ciguatoxins can kill fish, and there may be an upper limit of toxin that the fish can tolerate. But the picture is complex, since there are at least 5 Ciguatera fish toxins, including ciguatoxin (fat-soluble), maitotoxin (water-soluble), scaritoxin (found in parrot-fishes). The ciguatoxins, which activate voltage-dependent sodium channels, can be further broken down into ctx-1, 2, and 3, found in different concentraions, which may explain the variety of symptoms. 
  Symptoms can begin in as little as 15 minutes, or as long as 12-24 hours, but usually within 3-6 hours, getting worse over the next 4-6 hours. There is about 24-48 hours of nausea and vomiting, watery diarrhea, abdominal pain. Also neurologic symptoms occur, such as numbness or itching of the hands, feet and mouth; severe itching; muscle weakness; vertigo; to name a few of the many neurologic symptoms. The death rate is low, and usually caused by respiratory failure. About 2-5 days after ingestion, some people develop hot-and-cold tactile sensation reversal. The average illness lasts about 8 days. Occasionally, low blood pressure, low respiratory rate, and coma will occur.
  Itching can persist for weeks, and is worse with alcohol consumption, exercise, or heat. In severe cases, intermittent numbness, itching and muscle aches can last for up to 6 months.
  More severe illness occurs with repeat exposure to the toxin, since the toxin can accumulate in humans, as well as in fish.
  Treatment involves, preferably within 3 hours, emptying the stomach and administering activated charcoal. There is no antitoxin; supportive care, including monitoring blood pressure and breathing, is essential.
  During recovery, avoid fish, nuts, shellfish and alcohol, which worsen  symptoms.

Part 3 will discuss "other lovely fish toxins" -- Scomboid first, others by request.

Regards,
Leander
leander_at_worldnet.att.net

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