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

• Remove tentacles and nematocysts
• Hot water immersion

• Consider topical lidocaine
• Consider oral or parenteral analgesia for severe pain
• Acetic Acid may inhibit or trigger nematocyst discharge and thereby increase or decrease pain depending on species

• Avoid urine, ethanol, ammonia
• Avoid fresh or tap water since it causes nematocyst discharge via the osmotic gradient

• Symptomatic treatment for Irukandji syndrome
• Antivenom is available for severe box-jellyfish sting

See Also

• Marine toxins and envenomations

• Ward NT, Darracq MA, Tomaszewski C, et al. Evidence based treatment of jellyfish stings in North America and Hawaii. Ann Emerg Med. 2012;60(4:339-414.
• Cegolon L, Heymann WC, Lange JH, et al. Jellyfish stings and their management: a review. Mar Drugs. 2013;11(2): 523-50