Irukandji Jellyfish Facts and Information

Irukandji, scientific name Carukia Barnesi

The Irukandji, a small jellyfish with a bell approximately 2cm in diameter is responsible for the unusual and dramatic syndrome observed following stings commonly known as Irukandji Syndrome.  The Irukandji from its peanut sized body has a single retractile tentacle ranging from 50 to 500 mm long, hanging from each of the four corners of its bell.  Unlike most other species of jellyfish all parts of the Irukandji can sting and not just the tentacles. 

The initial sting of the jellyfish is usually not very painful.  However about 5 to 45 (in my case 10) minutes after being stung, the person starts to have a severe reaction, including backache, headache, shooting pains in their muscles, chest and abdomen.  They may also feel nauseous, anxious, restless and begin vomiting.  In rare cases the victim suffers pulmonary oedema (fluid on the lungs) which could be fatal if not treated or complete heart failure.

How do we know about them?

In 1964, a doctor called Jack Barnes spent several hours in a wetsuit lying in the water near Cairns searching for a specimen of the jellyfish responsible for 'Irukandji Syndrome'.  To Dr Barnes' delight, a thumbnail sized jellyfish swam past his mask.  He stung himself, his son and a surf life saver to check that the jellyfish he had caught was responsible for 'Irukandji Syndrome'.  All three ended up in hospital.  For Dr Barnes' dedication, the tiny jellyfish was later scientifically named Carukia barnesi.

Unlike the Chironex fleckeri (Box Jelly Fish), Irukandji are found mostly in the deeper waters of the reef, although they may be swept inshore by prevailing currents.  Divers and snorkellers are particularly at risk because of this and even though the waters are approx 30 degrees C, full body wetsuits are still recommend.

No definitive treatment is currently available for the Irukandji syndrome.  The Australian Venom Research Unit is currently involved in research to develop an anti-venom to treat Irukandji envenomation.  Advances in treatment for Irukandji stings have progressed since my sting in 2003 as anti-venoms such as the magnesium based one used to treat me are being tested throughout most Australian hospitals in areas close to Irukandji habitats.  Its normal habitat is in northern Australia, especially north Queensland.

Are Irukandji deadly?

In January 2002, a tourist swimming near Hamilton Island in the Whitsundays died after being stung by a jellyfish. His death was reported by the press to have been caused by an Irukandji.  The 58-year-old man had a pre-existing medical condition that made the jellyfish sting fatal.  He had a valve replacement and was taking warfarin to thin his blood.  After he was stung, his blood pressure increased which caused a brain haemorrhage leading to his death. The jellyfish that stung the man was not collected and its identity remains a mystery.

In April 2002, a second tourist died after being stung by a jellyfish while swimming at Opal Reef off Port Douglas in Queensland. The severe hypertension (high blood pressure) sometimes associated with Irukandji Syndrome caused a fatal brain haemorrhage.  The jellyfish which stung the second man was not collected. However, stinging cells (or nematocysts) collected from the man’s skin do not belong to Carukia barnesi or to any other known cubozoan (species in the same family).

Work is ongoing to find and identify the various types of jellyfish causing Irukandji Syndrome, especially those in the offshore islands and the Great Barrier Reef that cause the life-threatening symptoms of severely high blood pressure and heart failure.
 

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