Venomous Creatures: Cone Snail and Blue Ringed Octopus Envenomation

Mollusca is a hugely broad phylum of marine creatures, with everything from clams to octopuses. Animals in this phylum are characterized by a dorsal body wall which is usually firm with an opening for both the anus and genitals. Of the many types of molluscs, cone snails and the blue-ringed octopus are infamous for their venomous characteristics and dangerous interactions with humans. Cone snails alone account for 95% mollusc envenomations (1,2). 

Cone Snails

From: https://www.diversalertnetwork.org/health/hazardous-marine-life/cone-snails

Cone snails, also known as cone shells, are a venomous group of molluscs that contain a hollow proboscis with a venom soaked radula tooth (similar to a barbed harpoon), which is ejected and then discarded after use. Cone snails use this method for hunting, as well as for defense. Attacks on humans are usually defensive, but can be accidentally predatory (1). 

There are many different types of cone snail toxins (see table below) which each target different neurotransmitter receptors and ion channels. Some of these are classified by the US government as potential agents for bioterrorism (3,4).

Table: Cone Snail Venom Toxins

*considered a potential agent for bioterrorism

Victims of cone snail envenomation usually present with severe pain at the site of barb injection with local swelling and blanching, which can lead to tissue ischemia (3). Early systemic symptoms include syncope and cranial nerve deficits. Later in the course there may be muscle paralysis with respiratory failure or decreased consciousness leading to coma and death (3,5,6).

Prehospital Treatment:

• Remove patient from the water and closely monitor for cardiorespiratory collapse
• Pressure immobilization to stop lymphatic flow (7)
• DO NOT:
  • Suck out venom
  • Apply tourniquet
  • Try hot water immersion (8,9)

Emergency Department Management:

• Hemodynamically Stable
  • Antibiotics: ceftriaxone + doxycycline or monotherapy with a fluoroquinolone (as you need vibrio coverage)
  • Wound care, including tetanus
  • Analgesia

• Hemodynamically Unstable
  • Cardiorespiratory support, including intubation if necessary

Disposition:

• Admit: Systemic signs and symptoms or need for parenteral analgesia or surgical wound management
• Discharge: No systemic signs and symptoms and pain managed with oral analgesia

Blue-Ringed Octopus

From: https://www.diversalertnetwork.org/health/hazardous-marine-life/blue-ringed-octopus

The blue-ringed octopus delivers its venom by biting with a strong beak. The main toxin it delivers is tetrodotoxin, a potent sodium channel blocker that causes rapid-onset paresthesias, flaccid paralysis, and respiratory failure (2,5,6). Death can occur within minutes.

Initial bites are painless and often go unnoticed. Shortly afterwards, muscle paralysis sets in, and victims still underwater or far from shore succumb to drowning injuries. Any person seen having direct or close interaction with a blue-ringed octopus should be immediately removed from the water and monitored closely for systemic symptoms.

Prehospital Treatment:

• Remove from the water, and closely monitor for cardiorespiratory collapse
• Pressure immobilization to stop lymphatic flow (7)
• DO NOT:
  • Suck out venom
  • Apply tourniquet

Emergency Department Management:

• Wound care (including tetanus)
• Cardiorespiratory support

Disposition:

• Admit: Systemic symptoms or requirement for mechanical ventilation
• Discharge: No systemic symptoms after several hours of monitoring and need for simple wound care

Resources:

1. Kohn AJ.  Conus Envenomation of Humans: In Fact and Fiction. Toxins. 2019;11(10). https://doi.org/10.3390/toxins11010010
2. Fernandez I, Valladolid G, Varon J, Sternbach G.  Encounters with Venomous Sea LIfe. The Journal of Emergency Medicine. 2011;40(1):103-112. PMID: 20045606
3. Anderson PD, Bokor G.  Conotoxins: Potential Weapons from the Sea. J Bioterr Biodef. 2012;3(3):120 DOI: 10.4172/2157-2526.1000120
4. Select Agents & Toxins List [Internet]. Fed. Sel. Agent Progr. 2017 [cited 2019 Jun 19];Available from: https://www.selectagents.gov/exclusions-hhs-nontoxic.html
5. Balhara KS, Stolbach A.  Marine Envenomations. Emerg Med Clin N Am.  2014;32:223-243.
6. Hornbeak KB, Auerbach, PS.  Marine Envenomation. Emerg Med Clin N Am.  2017;35:321-337.
7. Pressure Immobilisation [Internet]. [cited 2019 Jun 19];Available from: https://www.poisonsinfo.nsw.gov.au/First-Aid/Pressure-Immobilisation.aspx
8. Halford ZA, Yu PYC, Likeman RK, Hawley-Molloy JS, Thomas C, Bingham JP. Cone shell envenomation: epidemiology, pharmacology and medical care. Diving and Hyperbaric Medicine. 2015;45(3):200-207.
9. Atkinson PRT, Boyle A, Hartin D, McAuley D.  Is hot water immersion an effective treatment for marine envenomation? Emerg Med J. 2006;23:503-508.

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