Marine Stings – Jellyfish

Stinging by jellyfish is caused by the simultaneous discharge of many thousands of microscopic stinging capsules called nematocysts. These are located on the surface of tentacles and in some species on the body of a jellyfish. Nematocysts contain coiled threads (tubules) loaded with venom. Upon contact, the nematocysts ‘discharge’ their tubules into the victim’s skin like mini harpoons. The more tentacles which make skin contact, the more venom is injected.

Stings cause immediate, sharp pain and an acute inflammatory skin reaction at the sting site consisting of redness, wheal and swelling which may progress to local skin destruction. Some stings cause rapid collapse. In Australia, life-threatening stings generally occur in tropical areas, with few in southern regions. Because of their smaller body size, children are at greater risk of the effects of envenomation.

Most stings are not serious and over-treatment of minor stings should be avoided. Wearing a full-body Lycra suit or equivalent provides good protection from stings.

Tropical Envenomation’s

Potentially fatal envenomation is caused by two jellyfish types in Australian Waters.

1. Box Jellyfish.

The Australian Box jellyfish, Chironex fleckeri, has a large (box-like) bell up to 20 x 30cm and multiple tentacles. It inhabits estuarine and onshore coastal waters. Contact with tentacles causes severe immediate pain and whip-like marks on the skin. A sting with several metres of tentacles can cause respiratory and cardiac arrest within a few minutes. Approximately 80 deaths have been recorded.

2. Jellyfish causing Irukandji syndrome

Approximately 10 small to medium-sized offshore and onshore jellyfish [including Carukia barnes and species of the Carybdea, Malo, Alatina, Gerongia and Morbakka genera] are known or suspected to produce an “Irukandji syndrome”. These jellyfish have only 4 tentacles and some are too small to be seen by the victim.

A minor sting on the skin with no tentacle visible, is followed in 5-40 minutes (typically 20-30) by severe generalised pain (often cramping in nature), nausea and vomiting, difficulty breathing, sweating, restlessness and a feeling of “impending doom”. Victims may develop heart failure, pulmonary oedema, and hypertensive stroke.

Prevention of further stinging

When a sting occurs, pieces of tentacles and non-discharged nematocysts may be left on the victim’s skin. In large or life-threatening stings, it is important to inhibit non-discharged nematocysts so that subsequent handling or treatment does not cause further envenomation.

Nematocysts from different species of jellyfish are either inhibited or stimulated to discharge by different substances used for first aid.

Vinegar

Vinegar (4-6% acetic acid) inhibits nematocyst discharge of Box jellyfish but does not provide pain relief from the venom already injected.

Although not proven to inhibit nematocyst discharge of all jellyfish causing Irukandji syndrome, its use is considered good first-aid practice.

Vinegar causes nematocyst discharge of some other jellyfish, including Bluebottle and is therefore recommended only for tropical areas where Box jellyfish and Irukandji stings occur.

Recognition

Since it is usually difficult to recognise which species of jellyfish has caused a sting, management is based on the risk of serious stings in the known geographical distribution of dangerous species. Life- threatening stings primarily occur along the tropical coastline of Australia.

Tentacles on the skin

  • Long lengths of easily visible large tentacles on the skin in association with severe pain should be regarded as Box jellyfish tentacles.
  • In the setting of large numbers of blue jellyfish washed up on the beach or floating on the surface of the water, tentacles are probably from a Physalia species (“Bluebottle”).
  • Tentacles from hundreds of other species of jellyfish in Australian waters are difficult to identify. Often no tentacles remain.

Skin markings

A variety of skin markings are associated with the stings of various jellyfish species and could include the following:

  • An inconspicuous mark which may develop a red flare.
  • An inconspicuous mark with goose pimples or an orange-peel appearance
  • An inconspicuous mark with profuse sweating only at the sting site
  • An irregularly shaped blotchy wheal
  • White wheals with a surrounding red flare
  • Multiple whip-like wheals on the skin or a “frosted ladder pattern” suggest a sting by a box jellyfish.
  • Later blistering or darkening of the sting pattern.

Pain

  • Skin pain is generally immediate and varies in intensity from mild irritation to very severe sharp or burning pain.
  • Generalised muscle aches
  • Severe muscle cramps in the limbs, chest, and abdomen.

Symptoms and signs of severe stings

  • Difficulty or cessation of breathing
  • Cardiac arrest
  • Severe pain
  • Restlessness and irrational behaviour
  • Nausea and vomiting, headache
  • Physical collapse
  • Profuse sweating, sometimes only in the sting area.

First Aid Management

No one nationwide recommendation for first aid can be made because of the difference between jellyfish around Australia.

In most cases, first aiders are unlikely to be able to identify the specific jellyfish.

In the tropics, because of the risk that the victim has been stung by a potentially life-threatening jellyfish, your priority is to preserve life.

Outside the tropics, where huge numbers of non-life-threatening stings occur, the primary object is to relieve the victim’s pain by using heat or cold.

Tropical Australia Management

  • D.R.S.A.B.C.D. and call an ambulance.
  • Remove the victim from the water and restrain if necessary.
  • Assess the victim and commence resuscitation as necessary.
  • Liberally douse/spray the stung area with vinegar for 30 seconds to neutralise invisible stinging cells, then pick off remaining tentacles.
  • If vinegar is unavailable, pick off any tentacles (this is not harmful to the rescuer) and rinse the sting well with sea water.
  • Apply a cold pack or ice in a dry plastic bag for analgesia, do not allow or apply fresh water onto the sting because it may discharge any remaining capsules.

Non-tropical Australia Management

  • Keep the victim at rest, reassure and keep under constant observation.
  • Do not allow rubbing of the sting area.
  • Pick off any tentacles (this is not dangerous to the rescuer) and rinse the sting area well with sea water.
  • Place the victims stung area in hot water (no hotter than the rescuer can comfortably tolerate) for 20 minutes.
  • If local pain is unrelieved by heat, or if hot water is unavailable, apply a cold pack or ice in a dry plastic bag.

If pain persists or is generalised, if the sting area is large, or involves sensitive areas call an ambulance.