ACMT Toxicology Visual Pearl – Master of Deceit

4. Stonefish

Background [1,2]

The stonefish is a member of the scorpion fish (Synanceia spp.) family. It hunts by ambushing prey utilizing extensive camouflaging and sitting motionless on the ocean floor. Stonefish are primarily located in the Indo-Pacific, with reports of their presence off the coast of Florida and the Caribbean. Most have between 12 and 14 venomous barbs on their dorsal surface. Encounters are common among SCUBA divers, anglers, and aquarium staff, although envenomation has occurred in recreational swimmers.

What does stonefish venom contain? [1,3,4]

Multiple components have been isolated from stonefish venom with species-to-species variation, but primarily considered to contain:

• Stonustoxin (SNTX) or Verrucotoxin (VTX) – systemic effects of hemolysis and cardiovascular collapse through cell membrane disruption and myotoxic effects
• Hyaluronidase – breakdown of connective tissue, facilitating local necrosis and spread of venom
• C-type Lectins – pro-inflammatory activity and nerve signaling contributing to intense pain

What are the symptoms of a stonefish envenomation? [1,2]

• Intense, excruciating pain out of proportion to the size of the injury
• Significant edema, which can spread proximally from the envenomation site
• Local necrosis and development of compartment syndrome
• Fever
• Delirium
• Muscle weakness and paralysis
• Pulmonary edema
• Hypotension and bradycardia
• Arrhythmia
• Deaths are reported but widely debated, with single-digit cases reported in the 21^st century

How do you treat a stonefish envenomation? [2,3,5-8]

• Hot water immersion therapy (42-45° C x 20 minutes)
• Pain control (opioids, local anesthetics, nerve blocks)
• Elevation/ compression
• Prophylactic tetanus vaccination and antibiotics
• Surgical removal of spines if present
  • X-ray imaging is most sensitive for identification, preferred over MRI or US
• Surgical management of local necrosis or compartment syndrome
• IV fluid or vasopressors as needed for hypotension
• Stonefish Antivenom [8]
  • Equine-derived IgG Fab
  • Produced in Australia, availability is limited outside of the South Pacific
  • Indications: protracted severe pain despite analgesia or systemic symptoms
  • Dosing – 1 vial antivenom

Bedside Pearls

• Maintain high suspicion for stonefish envenomation in endemic areas, or among collectors of exotic marine creatures, with patients presenting with pain out of proportion to exam after possible exposure.
• Prioritize hot water immersion therapy and stonefish antivenom for treatment, if available.
• X-ray imaging is preferred for the identification of retained spines.
• Surgical intervention may be required for retained spines, local necrosis, or compartment syndrome.