Ciguatera, Scombroid, & Tetrodotoxin

Ciguatoxin

The Set Up: You likely have been diving in an equatorial climate, in a 3mm wetsuit or board shorts. Just a few hours after eating some reef fish, you feel a weird tingling around your lips and face, followed by excruciating nausea, vomiting, diarrhea, and muscle fatigue. This is likely an episode of Ciguatoxin poisoning.

What is it: Ciguatoxin is produced by the dinoflagellate Gambierdiscus toxicus. These dinoflagellates live on coral and sea-floor associated algae. In fish that feed on coral, ciguatoxin accumulates in their viscera, head, skin, and roe. In the ruthless irony known in the ocean ecosystem, these tiny toxins climb an impossible food chain to the largest of fish on the reef. It is common to find ciguatoxin in grouper, wrasse, trigger fish, lionfish, roi, amberjack, barracuda, snapper, hogfish, and king mackerel. Cooking does not destroy the toxin.

Geography: The figure below shows approximate area of distribution. Ciguatoxin occurs in the Caribbean Sea, Hawaii, Central America, South Pacific, East and West Africa, and even in the Red Sea. Always talk to the locals for accurate information.

Prevalence and fatalities: 50,000 cases a year, <0.1% are fatal.

Mechanism: Lipophilic sodium channel activator. In other words, this molecule has access to most cells in the body and especially likes to aberrantly overstimulate neurons in your brain and musculoskeletal system.

Presentation: Symptom onset within 1-3 hours after consuming the fish with Ciguatoxin. Expect to experience nausea, vomiting, diarrhea, numbing sensation around the mouth/tongue, reversal of hot-cold sensations, significant muscle fatigue, at worse - some paralysis, very slow heart rate, palpitations, and low blood pressure. Symptoms fluctuate over the course of weeks to years, on an individual basis. It takes so long to recover from because new sodium channels must be built by your cells. It is so variable because each person has genetically unique capacity to heal.

Remedies: Induce vomiting immediately or eat activated charcoal to absorb the toxin. There is no antidote, treatment for this is supportive. If symptomatic, Benadryl can control itching. Dramamine or Zofran can be used to control nausea and vomiting. Be wary of dehydration due to vomiting, so force yourself to stay hydrated. Elavil (amitriptyline) is typically used as an antidepressant but can also reduce symptoms of paresthesia and fatigue. Vitamin B12 supplements support recovery but does nothing to reduce the toxin. If symptoms become serious go to the emergency room immediately and bring the fish, they won’t test it, but they will take you seriously because this is not seen frequently.

Legend has it: Feed questionable fish flesh to a cat and watch their response. Dab questionable fish on your tongue, if it has ciguatoxin it may cause your tongue to tingle or experience a hot-cold sensation.  

Many Hawaiian locals eat Roi (notorious for cig) their entire lives, yet do not exhibit symptoms like tourists do. The same is true for locals in Mexico and the South Pacific. Be mindful that where you grew up may play a significant role in your susceptibility to symptoms.

Scombroid

The Set Up: It is hot out and you are likely in an equatorial climate doing some blue water hunting. You start filleting your fish and realize that they haven’t been iced well at all. Within an hour of eating the meat you get an allergic reaction with hives. This is likely scombroid poisoning.

What is it: In the guts of mahi-mahi, yellowfin, blue fin, mackerel, bonito, and other pelagics, there exist the bacteria, Raoultella planticola and Morganella morganii. These bacteria proliferate at tropical temperatures, especially when you do not ice your fish! These bacteria contain the special enzyme, histidine decarboxylase, which converts the totally normal protein subunit histidine into histamine. Histamine underlies the typical allergic reaction, causing your airways to narrow and blood vessels to dilate and leak. The result is, wheezing with itchy, red hives. Unfortunately, histamine is heat stable and you can get sick despite cooking your fish.

Geography: Tropics.

Prevalence: Between 2000 and 2007 there were 865 affected individuals. The majority of cases occurred in Hawaii, Florida, and California; and no deaths were reported.

Mechanism: Bacterial enzyme unique to fish guts converts histidine to histamine, causing an allergy presentation.

Presentation: Symptom onset within 10-60 minutes of ingestion. Symptoms mimic an allergic reaction, including facial rash, sweating, dizziness, nausea, cramping, patchy hives on the body. Symptoms that should make you race to the ER include, low blood pressure, blurred vision, swelling of the tongue, and respiratory distress. Symptoms usually last less than 14 hours, and rarely exceed 2 days.

Remedies: Antihistamines, albuterol, possibly epinephrine.

Legend has it: Call up the pangero the night before and make sure they get ice.

Tetrodotoxin (TTX)

What is it: TTX is the venom of a pufferfish and blue-ringed octopus. TTX blocks sodium channels in your neurons so they cannot depolarize. This quite literally stops your neurons from propagating essential signals. TTX poisonings are reported most often in Japan, Singapore, Taiwan due to consumption of Fugu that was improperly cut. There are little to no reports of TTX poisonings by pufferfish stings. In Australia, Blue-ringed octopus bites also occur but not as frequently. Preparation of Fugu takes a decade to learn by master sushi chefs, such that they do not cut these toxin sacs contaminating the flesh. Fugu is reported to have an unique umami flavor.

Geography: Poisonings occur commonly in Japan, Singapore, Taiwan. You will see pufferfish species on reefs in the tropic zone (23°N to -23°S), Mexico, the Caribbean, and Indonesia.

Prevalence: From 2001 to 2006, 276 Japanese and Chinese individuals were poisoned, 21 died. In 2008, pufferfish sold in fish markets led to three outbreaks in Bangladesh, affecting 141 people, 17 of whom died from respiratory arrest.

Mechanism: Sodium channel block.

Presentation: Symptom onset occurs between 10 to 45 minutes after consumption of improperly prepared fugi. The symptoms of tetrodotoxin poisoning range from nausea, diarrhea, and generalized weakness to total incoordination, muscle spasticity, diaphragm paralysis, hypotension, and cardiac arrhythmias.

Remedies: If you ate the pufferfish, induce vomiting immediately. To do this, dump the contents of a saltshaker into a glass of water and drink it. Alternatively shove your fingers and hand beyond the back of your throat to induce the vomiting reflex. At the hospital they will do a gastric lavage. There is no other accepted anecdote for this.