The following information is taken from Wikipedia.

Ciguatera is a foodborne illness caused by eating certain reef fishes whose flesh is contaminated with toxins originally produced by dinoflagellates which live in tropical and subtropical waters.  These toxins occuring during harmfull algae blooms known as “red tide.”  These dinoflagellates adhere to coral, algae and seaweed, where they are eaten by herbivorous fish who in turn are eaten by larger carnivorous fish.  In this way the toxins move up the foodchain.  Gambierdiscus toxicus is the primary dinoflagellate responsible for the production of a number of similar toxins that cause ciguatera.  These toxins include ciguatoxin, maitotoxin, scaritoxin and palytoxin.  Predator species near the top of the food chain in tropical and subtropical waters, such as barracudas, snapper, moray eels, parrotfishes, groupers, triggerfishes and amberjacks, are most likely to cause ciguatera poisoning, although many other species cause occasional outbreaks of toxicity.  

Ciguatoxin is very heat-resistant, so ciguatoxin-laden fish cannot be detoxified by conventional cooking.

Symptoms

Hallmark symptoms of ciguatera in Humans include gastrointestinal and neurological effects.  Gastrointestinal symptoms include nausea, vomiting, and diarrhea, usually followed by neurological symptoms such as headaches, muscle aches, paresthesia, numbness, ataxia, and hallucinations.   Severe cases of ciguatera can also result in cold allodynia, which is a burning sensation on contact with cold (commonly incorrectly referred to as reversal of hot/cold temperature sensation).  Doctors are often at a loss to explain these symptoms and ciguatera poisoning is frequently misdiagnosed as multiple sclerosis.

Dyspareunia and other ciguatera symptoms have developed in otherwise-healthy males and females following sexual intercourse with partners suffering ciguatera poisoning, signifying that the toxin may be sexually transmitted.  Diarrhea and facial rashes have been reported in breastfed infants of poisoned mothers, it is likely that ciguatera toxins migrate into breast milk.

The symptoms can last from weeks to years, and in extreme cases as long as 20 years, often leading to long-term disability.  Most people do recover slowly over time.  Often patients recover, but symptoms then reappear.  Such relapses can be triggered by consumption of nuts, alcohol, fish or fish-containing products, chicken or eggs, or by exposure to fumes such as those of bleach and other chemicals.  Exercise is also a possible trigger.  Filipino and Chinese people may possibly be more susceptible.

info by Wikipedia