Travelling Studies

Just in time for the travel season, here is all you need to know to avoid an unpleasant surprise from that seaside feast on your next vacation.

A frequently overlooked source of food poisoning is toxins in seafood. Shellfish poisoning, fish poisoning, ciguatera, red tide illness, and sombroid are special hazards to travelers because the toxins typically do not affect the taste, smell, or appearance of the fish or shellfish. Moreover, cooking, drying, freezing, or smoking does not affect them.

Ciguatera poisoning occurs in coral reef fish that have consumed toxic algae. The highest concentrations of ciguatera toxins are found in the gut, head, liver, and roe, usually disdained by Western travelers. Since the toxin is concentrated up the food chain, ciguatera is most common in carnivorous fish weighing more than 6 pounds (2.5 kilos). Barracuda, sea bass, grouper, jack, and moray eel are the most common reservoirs of the toxin. Most ciguatera outbreaks occur in Florida and Hawaii, although the toxin also occurs in fish caught in the Caribbean.

Symptoms of ciguatera poisoning begin with abdominal cramps, diarrhea, nausea, and vomiting, with neurological sequelae, numbness and tingling in the arms, legs, and lips. There may be sensory reversal where cold objects feel hot; for instance, biting into an ice cream cone may cause a sensation of burning in the mouth. The teeth may feel numb or loose.

Symptoms may last weeks or months, and can be reactivated by eating alcohol, fish of any kind, or nuts.

Most cases of shellfish poisoning result from eating bivalve mollusks (clams, mussels, oysters, and scallops) that have been exposed to algal blooms or “red tides.” Fortunately, most cases have symptoms no worse than diarrhea, although amnesia, memory loss, and paralysis are not unknown. There is no medical treatment for shellfish poisoning.

Scombroid poisoning occurs after eating fish that has not been adequately chilled after capture. Tuna and related species contain high concentrations of the amino acid histamine. If the flesh is allowed to stand at warm temperatures, histidine is chemically converted to histamine, although the fish tastes, smells, and looks normal.

Histamine causes allergic reaction. Scombroid poisoning symptoms include abdominal cramps, diarrhea, flushing, headache, hives, nausea, and vomiting. Treatment with antihistamines (your product?) is very effective.

How do you avoid seafood poisoning?

• Avoid any fish that has a sharp, peppery taste even before it is seasoned (risk of scombroid poisoning).
• Avoid any fish that has an ammonia smell (risk of scombroid poisoning).
• Avoid reef fish that are larger than your plate (risk of ciguatera).
• Avoid shellfish harvested in areas suffering red tide
• Do not eat bivalve mollusks (clams, mussels, oysters, and scallops) in developing countries.
• If fish makes your tongue tingle, suspect ciguatera poisoning.