Answer: 4 – Tetrodotoxin
The pictured creature is a blue-ringed octopus (Hapalochlaena lunulate Hapalochlaena maculosa), and it secretes tetrodotoxin in its saliva (1). Tetrodotoxin binds voltage-gated sodium channels in muscles and nerve tissue, inhibiting action potential propagation and resulting in flaccid paralysis and death due to respiratory failure (2). The blue-ringed octopus has a beak-like structure
near its mouth that creates a small puncture wound, allowing for injection of venom from the salivary gland (3). Direct contact with the octopus’s tentacles does not cause envenomation. The blue ringed octopus is found in the Indo-Pacific oceans, particularly along the Australian coasts, and interestingly displays its colors only when threatened (4,5).
- Puncture wound at the site which can be red and itchy
- Perioral and intraoral paresthesia
- Blurry vision
- Nausea and vomiting
- Ataxia and weakness
- Within 30 minutes to several hours, progression to flaccid paralysis and respiratory failure, cardiac arrest, and death if untreated
- Does not affect mental status
- Paralysis lasts 4-10 hours, and treated patients recover fully in 2-4 days
- Local wound care and tetanus prophylaxis
- Close observation for symptom development
- Early airway management and supportive care for respiratory paralysis
- Fluid resuscitation and vasopressors if needed for hypotension
- No antivenom available
- If asymptomatic after 6 hours, can discharge from the Emergency Department
- Symptoms start within minutes and include oral paresthesia, vomiting, and weakness but can quickly progress to flaccid paralysis and respiratory failure.
- Management includes supportive care with a focus on respiratory support.
- Significant hypotension can occur and should be treated as needed.
- There is no antidote for tetrodotoxin poisoning.
- Use sedating agents while the patient is receiving mechanical ventilation as the venom does not cause CNS depression.
- Patients have good clinical outcomes if symptoms are recognized quickly and they are supported with mechanical ventilation during the paralysis.
- Most patients have complete resolution of symptoms within 2-4 days.