Hey all,
Scombroid. Ciguatera. Tetrodotoxin. Histamine poisoning.
Tired of getting these questions wrong on Rosh Review? Didn't realize that scombroid and histamine poisoning are the same thing?
Then this POTD is for you. Let's break down this topic together.
Scombroid: Think of histamine, and you'll get most questions correct regarding scombroid poisoning.
Background: Accounts for 40% of seafood borne illness in the US and Europe, most common states in Hawaii, California, Florida. Occur in outbreaks where everyone is eating the same batch of fish.
Symptoms: Flushing of face and neck, urticaria/pruritic erythematous rash, palpitations, dizziness, perioral burning and itching, edema, diarrhea, headache. Length of symptoms: 1-12 hours. Involves other members of family/friends who all ate the same food. Patients note that the fish has a "peppery" taste.
Rarely, upper airway edema, hypotension, or bronchospasm.
Delicious Jerks Responsible: Typically fish of the Scombridae families, including tuna, mackeral, bonito, skip jack. Also happens with mahi mahi, swordfish, marlin, herring, sardine, anchovies, salmon, tilapia, and trout. Also swiss cheese for some reason (more on that later).
Pathophysiology: Caused by consuming fish which have not been properly refrigerated after being caught. Poor refrigeration leads to bacterial overgrowth in the fish capable of decarboxylating histidine into histamine. Histamine builds up in the fish over time, and post ingestion gives the histaminergic symptoms described above. Foods with histamine concentrations exceeding 50mg/100g of food are considered to be hazardous. Accumulation of histamine oftentimes happens before the fish becomes "spoiled" and thus is approved for consumption. Scombroid is associated with swiss cheese because it is thought the raw milk used in the production of the cheese can be contaminated with the same bacteria able to produce histamine from histidine.
Histamine is NOT destroyed when cooking the fish.
Treatment: Antihistamines- H1 and H2 Antihistamines
Treatment is focused on combating the excess histamine-
H1: Diphenhydramine
H2 for moderate to severe symptoms: famotidine/cimetidine
For patients presenting with enough histamine to appear as if they are in anaphylaxis, treat them as your would any anaphylaxis patient.
Who is at risk for anaphylaxis like reaction? Patients taking something that inhibit histamine metabolism. This includes patients on isoniazid and MAO inhibitors.
Contact local public health to report scombroid poisoning.
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Ciguatera: Why do my teeth hurt? Why is my ice cream so HOT? The one with all the weird neuro-symptoms
Background:
Common on coastal regions; accounts for 20% of fish related foodborne illness in the US.
Fish containing ciguatera toxin appear normal. They do not taste or smell different than their non-ciguatera containing counterparts.
Symptoms: Vomiting, diarrhea, abdominal pain;
paresthesias, painful teeth, reversal of hot and cold sensation, perioral paresthesias, painful urination, cerebellar dysfunction including ataxia and vertigo, ;
rarely cardiorespiratory symptoms of bradycardia, heart block, hypotension, shortness of breath, respiratory distress.
Patients in multiple case studies report relapsing of symptoms. Though symptoms usually resolve in days to weeks, some report relapsing symptoms months and years down the line.
Delicious Jerks Responsible: The reefers (moray eel, amberjack, grouper, snapper, parrot fish, sea bass, and ooh, barracuda).
Pathophysiology: Fish eat dinoflagellates of the Gambierdiscus family that grow on coral reefs. These dinoflagellates produce ciguatera toxin that accumulates in the fish. The fish are not affected by the ciguatera. The toxin is also heat stable, meaning it will not be destroyed during cooking.
The toxin works by opening voltage-dependent sodium channels on cell membranes, triggering cell depolarization.
Treatment: Symptomatic treatment.
Start at your ABCs as always, as these patients rarely, though sometimes, require airway maintenance. Atropine if needed for bradycardia, pacing.
Antiemetics, IV hydration.
Sometimes recommended to use mannitol if neurological symptoms are present, though in an RCT of 50 patients by Schnorf et al, mannitol shown to have no benefit over normal saline in treating symptoms.
Gabapentin for neuropathic pain.
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Tetrodotoxin: The dangerous one; the one that can kill you
Background: Also known as pufferfish poisoning. Question stems usually involve someone eating fugu at a sushi restaurant.
Symptoms: Occur shortly after ingestion: parasthesia, headache, vomiting, diarrhea, abdominal pain
dysarthria, dysphagia, ascending paralysis, respiratory failure, and death.
Delicious Jerks Responsible: Pufferfish, angelfish, blue ringed octopus.
Pathophysiology: Produced by an endosymbiotic bacteria, tetrodotoxin is a neurotoxin that binds sodium channels, preventing sodium influx and preventing depolarization. Can cause paralysis; affects skeletal muscle interfering with respiration, causing respiratory failure, and with vascular smooth muscle, causing hypotension.
Treatment: Supportive care. ABCs, and if progressing to respiratory failure: intubation.
IVF
Can consider GI decontamination with stomach lavage and WBI if presenting to ED soon enough.
Some evidence suggests using anticholinesterases like neostigmine, though the evidence is weak and not shown to be effective in all patients.
Sources:
https://pubmed.ncbi.nlm.nih.gov/2689658/
https://wikem.org/wiki/Scombroid
https://pubmed.ncbi.nlm.nih.gov/11914401/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4626696/
https://pubmed.ncbi.nlm.nih.gov/25410493/