Octopuses, which are organisms of the class Cephalopoda in the phylum Mollusca, are generally harmless and unlikely to be aggressive unless provoked.
Their bites are rarely life threatening, except for the bite of the greater blue-ringed octopus, Hapalochlaena lunulata and the southern blue-ringed octopus (also known as the Australian spotted octopus) Hapalochlaena maculosa, which are found in coastal waters and tide pools around Australia and other Western Pacific tidal pools.[1, 2] A third species, the blue-lined octopus Hapalochlaena fasciata, has also been described. These octopuses grow up to 20 cm in length with tentacles extended. They are normally light-colored with dark brown bands and blue rings or patches. When disturbed, their bodies darken, and the blue circles turn iridescent blue. Their venom can be released into the water to paralyze their prey, but its effects on humans primarily occur by injection of the venom upon biting.[3, 4, 5, 6, 7]
The blue-ringed octopus is shown below.
Blue-ringed octopus. Image courtesy of Simon Dubbin.
There are many fractions in the venom secreted from the salivary glands of the blue-ringed octopus, one of which is identical to tetrodotoxin. This substance has also been found in multiple other tissues in H lunulata and H fasciata through fluorescent light microscopy. Tetrodotoxin blocks voltage-gated fast sodium channel conduction, blocking peripheral nerve conduction, which can lead to paralysis and death from respiratory failure. Nerve conduction studies in tetrodotoxin-poisoned (puffer fish) persons have demonstrated reduced motor and sensory conduction velocities consistent with inhibition of sodium currents at the node of Ranvier. Reported central nervous system effects of tetrodotoxin in humans have included nausea and emesis, miosis, diabetes insipidus, and depressed cortical activity.
Other fractions of the venom include 5-hydroxytryptamine, hyaluronidase, tyramine, histamine, tryptamine, octopamine, taurine, acetylcholine, and dopamine.
The blue-ringed octopus does not naturally dwell in the coastal waters of the US.
Rare cases of octopus envenomation occur in the Indo-Pacific region.
Mortality is rare. Full recovery is expected when appropriate measures are undertaken.
Individuals bitten by a blue-ringed octopus would have to be old enough and mobile enough to be able to walk or swim in the tide pools and coastal waters of Australia.
Any octopus can bite with its parrot-like chitinous beak.
The bite of the blue-ringed octopus is usually painless; however, the individual may experience a reaction similar to a bee sting.
If envenomation has occurred, symptoms are likely to start within 10 minutes of being bitten.
If a significant envenomation has occurred, the individual will rapidly progress from perioral and peripheral paresthesias through the following signs and symptoms.
Anaphylactoid or anaphylactic reactions have rarely been reported.
The individual is usually bitten on an extremity and sustains 1-2 small puncture wounds.
Local reaction may be minimal, but it can progress to include pain, edema, and erythema of the entire extremity.
The patient becomes flaccid once paralyzed.
Envenomations usually occur when an individual picks up a blue-ringed octopus or accidentally steps on one.
Laboratory studies for octopus envenomation are noncontributory.
A general workup for a critically ill patient is recommended to rule out other etiologies for acute paralysis and respiratory failure.
Imaging studies are generally not helpful.
A plain film of the puncture site may be indicated to rule out a foreign body.
Cardiopulmonary support, including endotracheal intubation and cardiopulmonary resuscitation (CPR), as clinically indicated.
What constitutes proper wound care for octopus envenomation is controversial. Options include the following:
Treatment of octopus envenomation is supportive.
Provide endotracheal intubation and ventilatory support until the venom has worn off, usually within 4-10 hours.
Confirm that the patient's tetanus status is current.
No antivenin is available.
Neostigmine and edrophonium have shown benefit in restoring muscular strength in some cases of tetrodotoxin intoxication (eg, puffer fish), but have not undergone clinical trials in blue-ringed octopus envenomations.
4-Aminopyridine (Neurelan - US, Pymadine), a drug utilized as an antagonist to nondepolarizing neuromuscular blocking agents (available in the US as an orphan drug for multiple sclerosis), has been shown to reverse tetrodotoxin toxicity in animal experiments.
A general surgery consult may be indicated for wide excision of the wound. However, this has not proven to improve outcome.
A medical toxicologist (certified by the American Board of Medical Toxicology or the American Board of Emergency Medicine), or a poison control center certified by the American Association of Poison Control Centers, should be contacted regarding this uncommon intoxication.
The goal of pharmacotherapy is to reduce morbidity and prevent complications. Administration of nondepolarizing neuromuscular blocking antagonists may be beneficial. 4-Aminopyridine (Neurelan) is utilized as an antagonist to nondepolarizing neuromuscular blocking agents (available in the US as an orphan drug for multiple sclerosis), has been shown to reverse tetrodotoxin toxicity in animal experiments.[11, 2] The dosing regimen for use in octopus envenomation is not yet established.
The patient with octopus envenomation should be admitted to an intensive care unit until the venom has worn off, usually in 4-10 hours.
If significant hypoxia has not occurred, recovery is usually rapid.
Local wound care follow up is prudent.
If acute paralysis and respiratory arrest is not immediately recognized and appropriately treated, anoxic brain injury or death will result.
The prognosis for octopus envenomation is generally excellent, unless significant hypoxia has occurred.
Patients should be warned that anaphylactic reactions may result in ongoing symptoms (eg, joint pains, effusions) for up to several weeks.