Nematocysts

Mechanism

• Jellyfish; Box Jelly is most deadly
• Most toxic: Australia and other Indo-Pacific waters

Nematocyst stages of discharge

• Physical contact or osmotic gradient causes discharge of neamtocysts
• A spring loaded venom delivery system

Clinical Features

• Isolated stinging
• Severe
  • Respiratory paralysis, cardiovascular collapse, limb paralysis and death
  • Irukandji syndrome - myalgias, back, chest, abdominal pain, nausea, vomiting, diaphoresis, hypertension, tachycardia, hypertension, myocardial injury, pulmonary edema

Differential Diagnosis

Marine toxins, envenomations, and bites

• Toxins
  • Ciguatera
  • Scombroid
  • Tetrodotoxin (e.g. pufferfish)
  • Shellfish poisoning
    • Amnesic shellfish poisoning
    • Diarrheal shellfish poisoning
    • Neurotoxic shellfish poisoning
    • Paralytic shellfish poisoning
• Stingers
  • Stingray injury
• Venomous fish
  • Cone shell
  • Lionfish
  • Sea urchins
  • Crown-of-Thorns Starfish
  • Stonefish
  • Other: Catfish, zebrafish, scorpion fish
• Nematocysts
  • Coral reef
  • Fire coral
  • Jellyfish (Cnidaria)
    • Box jellyfish
      • Irukandji syndrome
    • Sea wasp
  • Portuguese man-of-war
  • Sea anemones
  • Seabather's eruption
• Phylum porifera (sponges)
• Bites
  • Alligator and crocodile attacks
  • Octopus bite
  • Shark bite
• Infections
  • Vibrio species in saltwater
  • Aeromonas species in freshwater

Management

• Immerse in 5% acetic acid to inactivate nematocysts
• Alternatives
  • Immersion in rubbing alcohol (isopropyl 40%)
  • Acidic drinks such as flavored sodas and fruit juices may be helpful
  • Baking soda
• Avoid fresh or tap water since it causes nematocyst discharge via the osmotic gradient
• Antivenom is available for severe box-jellyfish sting

See Also

• Marine toxins and envenomations