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Author: Dr Kirsten Due, General Practitioner, South Australia, Australia. DermNet New Zealand Editor in Chief: Hon A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand. Copy editor: Maria McGivern. May 2017.
Images courtesy of Professor Bart Currie, Menzies School of Health Research, Darwin, Northern Territory, Australia.
The Australian box jellyfish or Chironex fleckeri, more commonly known as a sea wasp or ‘stinger’, is a species of venomous and deadly box jellyfish found off the coast of tropical Australia.
The Australian box jellyfish is an invertebrate marine animal of the phylum cnidaria (Gk. ‘stinging object’), named in honour of radiologist Dr Hugo Flecker (1884–1957). Cnidaria (‘nid-AIR-ee-ah’) are vast in variety. They comprise four main classes:
Of the 10,000 known species of Cnidaria, about 100 are potentially dangerous to humans. The Australian box jellyfish, has been responsible for over 70 fatal stings or ‘envenomings’ since 1883. Cubozoans also include several species of four tentacled box jellyfish that cause Irukandji syndrome.
Australian box jellyfish specimens have weighed up to 6 kg; they are composed of a large umbrella-like bell with four bundles of tentacles arising from the corners of the bell. The box jellyfish is difficult for victims to see, and harder to avoid, with their near-transparent tentacles extending up to 300 mm. Their stings injure the skin and can cause severe systemic effects. They feed on small prawns.
The Australian box jellyfish is found in coastal waters from northern Australia but its distribution can now be widened to include nearby areas of the Indo-West-Pacific Ocean. Their northern-most reach has yet to be found, and their overall biogeography is uncertain.
Until recently, it was thought that Australian box jellyfish were rare in deep waters as marine surveys of the Great Barrier Reef found few away from the shore or deeper than 5 m. However, an opportunistic deep-sea video study in North-western Australia found large numbers at depths of 39–56 m (64 in a 1500 m tow or 0.05 m−2).
Stings from the Australian box jellyfish are difficult to study because:
Envenomation (or stinging) occurs when human skin contacts the thousands of densely packed nematocysts that line the jellyfish tentacles. Within 700 Ns of contact, the nematocyst capsules fire thousands of barbed, poison-filled darts. These travel 67 km/hour with an impact pressure on the epidermis of 7.7 GPa (about 1,116,790.5 psi).
TheAustralian box jellyfish toxin is injected into the skin. It has direct effects on muscle and nerves, and can cause chronic immunological complications.
Most Australian box jellyfish stings are a nuisance rather than a medical threat. The seriousness of the sting relates to the size of the box jellyfish (those with a bell over 150 mm are considered highly dangerous).
Skin symptoms occur immediately upon contact and include:
The response to Australian box jellyfish envenomation varies from person to person, depending on how well the dermis can clear irritant chitins (the jellyfish exoskeleton) from the skin.
Systemic features of Australian box jellyfish envenomation may include:
If the total estimated length of welts is over 700 mm, unconsciousness follows rapidly, culminating in a painful death after 5–20 minutes.
With their lower body-mass, children are most vulnerable.
Death from Australian box jellyfish envenomation is largely due to the rapid cardiovascular effects of pore-forming toxins. Autopsies reveal pulmonary oedema.
The spiny darts that explode into the epidermis are made up of collagens, glycoproteins and polysaccharides. These may trigger antigenic and innate immune responses, separate from the toxins they carry. Angioedema and anaphylaxis may occur.
Diagnosis of Australian box jellyfish envenomation depends on noting the typical clinical features and sighting a responsible jellyfish. A definitive diagnosis is based on the characteristic nematocysts from the Australian box jellyfish being found. Sticky tape can be used to collect skin samples for research and identification purposes.
First-responder treatment includes getting the person out of the water while not endangering the rescuers.
A clothed rescuer is unlikely to sustain envenomation as the nematocysts from the Australian box jellyfish do not effectively puncture even thin clothing.
Heat is not recommended as part of standard treatment, although it can reduce the venom lethality when maintained at over 43 C as the use of heat may deter more valuable efforts at symptom control and resuscitation.
Do not apply pressure immobilisation bandages, as these may trigger further toxin discharge.
Cnidarian venoms have been investigated as a potential source of novel bioactive therapeutic compounds. Collagen from the Australian box jellyfish bell enhances immunoglobulins M and G, interferon and tumour necrosis factor production by human lymphocytes, as well as enhancing inflammatory cytokine secretion, antibody secretion and causing population changes in immune cells.
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