Box Jellyfish Envenomation

The Box Jellyfish (Chironex Fleckeri), also known as the ‘Sea Wasp’, is the most venomous jellyfish known and is considered one of the most venomous marine creatures on the planet. It is found only in tropical Australian waters and although sightings are most common during summer months, it is present in estuarine outflow regions all year round. It has been responsible for at least 60 human deaths in Australia alone.

It is a large virtually transparent jellyfish with a square shaped body and numerous tentacles extending from each of the four corners. Each tentacle contains millions of individual stinging cells called nematocysts.

Box Jellyfish venom

The Box Jellyfish venom is difficult to collect and as such is still a bit of a mystery. The multi-component venom causes severe local pain and tissue necrosis as well as having effects on heart and lung functions. Death from severe envenomation is usually very rapid (within minutes) with cardiac arrest often occurring before the victim manages to get out of the water.  Significant Box Jellyfish envenomation carries a 100% death rate without antivenom treatment.

Symptoms of envenomation

The symptoms of Box Jellyfish envenomation will be dependent on the area of skin that has come into contact with the treacherous tentacles. Involvement of >10% of the body skin surface is invariably fatal without antivenom treatment.

The initial indication of tentacle contact is immediate excruciating pain at every contact point of the tentacles with the skin. This will often progress to the development of red raised welts and then blistering and ulceration. The pain is often so severe that the victim is unable to talk or move.

If severe envenomation the victim may develop breathing difficulties and full cardiac arrest within 4-5 minutes of contact.

First Aid in the field

Any potential victim should be safely removed from the water ensuring no risk of envenomation to First Aid givers. Basic Life Support should be commenced and assistance sought immediately.

The affected area should be flooded in Vinegar. Vinegar will not reduce the pain or reverse envenomation already occurred but will inactivate and prevent further firing of nematocysts that may come into contact with the skin. Ensure the victim (or bystanders) does not rub the envenomated skin as this will potentially activate firing of more nematocysts

No attempt should be made to capture the offending jellyfish. The most likely outcome of inexperienced hands trying to capture a Box Jellyfish is envenomation and not many live to tell their story!

Antivenom

CSL Box Jellyfish Antivenom is specific for neutralising the venom of the Box Jellyfish (Chironex Fleckeri). The antivenom is produced from sheep serum.

The antivenom should only be administered if there is clear evidence of symptoms of envenomation.

Although intravenous antivenom is preferable, it may be administered in the field as an intramuscular injection by experienced medical or paramedical personnel. All victims of envenomation require transport to hospital. The initial dose is three ampoules and this should be administered at the first sign of any envenomation effects. The dose should be repeated as required according to response to treatment.

The risk of anaphylaxis to the antivenom is low however capacity to manage anaphylaxis must be available.

Following antivenom

• The tetanus immunisation status of the victim should be checked and updated if necessary
• The victim should be observed for a minimum of 12 hours following full resolution of symptoms of envenomation
• The victim should receive advice on the potential to develop serum sickness