Nematocysts

Background

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

• 

  Box jellyfish

• 

  Coral reef

• 

  Portuguese Man-O-War {Physalia physalis)

• 

  A selection of various sea anemones

Nematocyst Mechanism

Nematocyst stages of discharge

• Physical contact or osmotic gradient causes discharge of nematocysts
• A spring loaded venom delivery system
• Once opened, a nematocyst releases all of its contained venom

Clinical Features

Skin lesion after contact with the cubomedusa Chiropsalmus quadrumanus jellyfish

• Isolated stinging, pain
• Severe
  • Limb paralysis
  • Respiratory paralysis
  • Cardiovascular collapse
  • Death

Irukandji syndrome

• Usually develops within 2 hours of envenomation & can last up to 2 days
• Rare but potentially fatal complication. It often involves intense pain, diffuse muscle cramps, vasconstriction and marked hypertension due to a catacholamine surge.
  • Beware of hypertensive emergency: Look for signs of end organ damage (ie ACS, CHF, intracranial hemorrhage, renal injury)

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

Evaluation

• Generally a clinical diagnosis

Management

• Remove tentacles and nematocysts
• Hot salt water immersion (inactivates heat labile toxins), submerging the area in 45 ℃ water for 20 minutes has been shown to provide significant pain relief
• Stingose is a topical solution composed of 20% aluminum sulfate and 1.1% surfactant.
  • Used for pain control, venom removal via osmosis, & venom neutralization via denaturation of proteins and polysaccharides through interactions with the aluminum ion.
• Consider topical lidocaine
• Consider oral or parenteral analgesia for severe pain
• In general, avoid acetic acid (vinegar) since it mostly increases the firing of nematocysts and therefore increases pain.
  • Some evidence that it does inhibit nematocyst discharge in the Australian Box Jellyfish species
    • Box Jellyfish: 4-5% acetic acid solution should be applied to the injured area for at least 30 seconds.
• Symptomatic treatment for Irukandji syndrome
  • Consider fentanyl for pain and antihypertensives such as magnesium sulfate and nitroglycerin
• Antivenom is only readily available in Australia for severe box jellyfish sting

Avoid

• Urine, ethanol, ammonia,
• Acetic acid/vinegar (unless box jellyfish)
• Fresh or tap water (causes nematocyst discharge via the osmotic gradient)

See Also

• Marine toxins and envenomations
• Sea wasp

References

1. 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.
2. Cegolon L, Heymann WC, Lange JH, et al. Jellyfish stings and their management: a review. Mar Drugs. 2013;11(2): 523-50