ciguatoxin

Ciguatoxins are a class of toxic polycyclic polyethers found in fish that cause ciguatera.

There are several different chemicals in this class. "CTX" is often used as an abbreviation.

Ciguatoxin 1 - {{PubChem|5311333}}
Ciguatoxin 2 - {{PubChem|6441260}}
Ciguatoxin 3 - {{PubChem|6444399}}
Ciguatoxin 4B (Gambiertoxin 4b) - {{PubChem|6450530}}

Toxic effect on humans

Ciguatoxins do not seem to harm the fish that carry them, but they are poisonous to humans. They cannot be smelled or tasted and cannot be destroyed by cooking.{{cite journal|vauthors=Swift AE, Swift TR|year=2008|title=Ciguatera|journal=Journal of Toxicology. Clinical Toxicology|volume=31|issue=1|pages=1–29|doi=10.3109/15563659309000371|pmid=8433404|s2cid=222017205 }} Rapid testing for this toxin in food is not standard.

Some ciguatoxins lower the threshold for opening excitatory voltage-gated sodium channels in the nervous system. Opening a sodium channel causes depolarization, which could sequentially cause paralysis, heart arrhythmia, and changing the senses of heat and cold. Such poisoning from ciguatoxins is known as ciguatera.

Ciguatoxins are lipophilic, able to cross the blood–brain barrier, and can cause both central and peripheral neurologic symptoms.

The major symptoms will develop within 1–3 hours of toxin ingestion: vomiting, diarrhea, numbness of extremities, mouth and lips, reversal of hot and cold sensation, muscle and joint aches. The symptoms may last from days to weeks or even months depending on each individual situation. There is no known antidote, though several therapeutic targets have been identified.{{cite journal | vauthors = Vetter I, Touska F, Hess A, Hinsbey R, Sattler S, Lampert A, Sergejeva M, Sharov A, Collins LS, Eberhardt M, Engel M, Cabot PJ, Wood JN, Vlachová V, Reeh PW, Lewis RJ, Zimmermann K | title = Ciguatoxins activate specific cold pain pathways to elicit burning pain from cooling | journal = The EMBO Journal | volume = 31 | issue = 19 | pages = 3795–808 | date = October 2012 | pmid = 22850668 | pmc = 3463840 | doi = 10.1038/emboj.2012.207 }}{{cite journal | vauthors = Patel R, Brice NL, Lewis RJ, Dickenson AH | title = Ionic mechanisms of spinal neuronal cold hypersensitivity in ciguatera | journal = The European Journal of Neuroscience | volume = 42 | issue = 11 | pages = 3004–11 | date = December 2015 | pmid = 26454262 | pmc = 4744673 | doi = 10.1111/ejn.13098 }} The LD₅₀ of ciguatoxin in mice is around 200 to 300 ng/kg.{{Cite book|last1=Fusetani|first1=Nobuhiro|url=https://books.google.com/books?id=ZfhDAAAAQBAJ&q=ciguatoxin+ld50&pg=PA9|title=Marine Toxins as Research Tools|last2=Kem|first2=William|date=2009-01-31|publisher=Springer Science & Business Media|isbn=978-3-540-87895-7|language=en}}

Bioaccumulation

Ciguatoxin is produced by Gambierdiscus toxicus, a type of dinoflagellate. The phenomenon occurs in the Caribbean Sea, Hawaii, and coastal Central America. The toxin usually accumulates in the skin, head, viscera, and roe of big reef fish like grouper, wrasse, triggerfish, lionfish, and amberjack. It also affects barracuda, snapper, hogfish, king mackerel, and sea bass.{{Cite web|title=Fishes Carrying This Incurable Poison Are on the Rise|url=https://medium.com/microbial-instincts/fishes-carrying-this-incurable-poison-are-on-the-rise-2de5de37509b|last=Yong|first=Shin Jie|date=2020-04-19|website=Medium|language=en|access-date=2020-05-25}}