Irukandji Syndrome [48]

Just When You Thought it Was Safe to go Back in The Water

By Trevor Gardner

She felt a small sting behind her right armpit, after which she left the water and took a warm shower. Approximately 10 minutes after the sting she noticed aching and cramps in her legs, then generalised muscular aching, with sweating and dry retching… on arrival at the hospital she was sweating profusely, shaking violently and complaining of generalised pain. She had generalised piloerection, irregular rapid heart beat and marked high blood pressure. At this stage, she was very distressed and felt that she “was about to die” (an opinion shared by her medical attendant!).

The Irukandji people are an indigenous tribe that lived near Cairns in Far North Queensland (FNQ). Stings caused by the small jellyfish Carukia barnesi were mostly reported in the area around where the Irukandji lived. In 1952 Flecker coined the name Irukandji syndrome to describe the severe prostration typified by backache, muscle pains, chest and abdominal pains, headache, nausea, vomiting and restlessness, together with localised piloerection (hair standing on end), localised sweating, high heart rate and high blood pressure. There is no anti-venom available.

The Irukandji syndrome has been increasingly discussed in the medical literature during the 80s and 90s. Most information relates to describing the spectrum of symptoms, where and when people were stung and various treatments. Very little hard research has been done on the Carukia until the last few years. In fact, the Irukandji syndrome may be caused by up to seven species of small jellyfish but typically when the literature talks of envenomation by the ‘Irukandji’ they are referring to Carukia barnesi.

How relevant is the Irukandji to the average sea kayaker? Not at all as long as you never paddle further north than Hervey Bay near Fraser Island in Queensland or further north than Dampier on the lower NW coast of Western Australia. As long as you never paddle in the finest several thousand kilometres of coastline in the world then you can stop reading now.

If you only paddle in the middle of the year for the three or four months of the southern winter then you are pretty safe as well. Most other months of the year Irukandji envenomation is reported, peaking in December to February. Irukandji envenomations vary yearly but in the north of Queensland there about 100 to 200 stings reported in a bad season. On Christmas Day in 1985 the emergency department of Cairns Hospital in FNQ had 36 Irukandji syndrome presentations.

Apart from the tropical waters of the east and west coasts of Australia, the Irukandji is occasionally reported in the islands of the Indian and Pacific Oceans (including Indonesia and Fiji). The distribution could be much wider.

Palm Cove, about 25 km north of Cairns, has the highest percentage of envenomations. Backwise multiple regression analysis of the weather in FNQ shows that lighter than average northerly winds, hotter than average days and lower than average rainfall in the past seven days was significantly associated with presentations of the Irukandji syndrome in presentations to Cairns Hospital.

Carukia barnesi is a member of the class Cubozoa, as is the more dangerous Chironex fleckeri (Box Jellyfish). However, Carukia is part of the family Carybdeidae whereas Chironex is from the family Chirodropidae. The Carukia is a small clear jellyfish, measuring 20 mm in diameter and 25 mm in the depth of its bell. There are four tentacles, one from each corner, which contain a large number of nematocysts (stinging cells). The tentacles may extend from 5 cm to 1 metre in length, depending on the degree of contraction.

The bell of the Irukandji (Carukia) also contain nematocysts which can cause envenomation. The Irukandji is rarely seen before one is stung (or after) and it has been historically very difficult to catch the Irukandji for research. Imagine a creature with a clear body, in water, the size of the end of your thumb with a potentially lethal sting, and there you have the Irukandji.

The nematocysts (stinging cells) have much in common with other stinging jellyfish such as the Chironex and Blue Bottle (Physalia). Each of the numerous nematocysts are like tiny spring loaded hypodermic needles. Contact with the skin causes the nematocyst to discharge and inject a tiny amount of venom. The more contact, the greater the amount of venom injected. Becoming all excited and thrashing about is a great way to ensure further contact with the micro injectors. In general, however, the small nature of the Carukia and lack of impressive initial sting does not lead to large areas of contact.

The issue of vinegar (acetic acid) as a first aid measure warrants a mention. Vinegar is well recognised as an important first aid measure in Chironex stings. As little as 30 seconds exposure of the Chironex tentacles to 5% acetic acid (household vinegar is 4.2–5.5% acetic acid) will prevent further nematocysts from firing. The tentacles are then removed carefully, preferably while applying more vinegar. However, the nematocysts of other jellyfish, including the Blue Bottle, are triggered by vinegar. The nematocysts of the Irukandji (Carukia) are inactivated by vinegar when studied in the laboratory. Recent work in Cairns showed no evidence of adverse effects from the application of acetic acid (vinegar) to Irukandji stings and these authors include vinegar at the top of their Irukandji treatment algorithm. The effects of vinegar in treating an Irukandji envenomation may be limited due to the delay in recognising the sting. Once the symptoms are obvious it appears there are few if any active nematocysts left on the skin. However, vinegar would seem to be a reasonable first aid measure if available, especially if commenced early.

In 1943 during WW2, Dr Ron Southcott observed the envenomation of a group or troops and described the bizarre set of distressing symptoms, calling them ‘type A’ stings to differentiate them from ‘type B’ stings, later known to be caused by the Box Jellyfish. In 1966 Dr Jack Barnes captured a small 20 mm ‘box’ jellyfish with a tentacle in each corner. He then stung himself, his son and a volunteer lifesaver to see if it caused the Irukandji syndrome. All three ended up in the Cairns Base Hospital intensive care unit with severe and typical Irukandji syndrome. Southcott later named the jellyfish Carukia barnesi.

Unlike the Box Jellyfish, the Carukia is an open water creature and found in deeper waters of the reef and the islands, at depths up to 10-20 metres. Divers and snorkellers are particularly at risk but prevailing currents and winds can sweep the Carukia inshore causing a relative mass stinging of bathers thought to be protected by the stinger nets designed for the Box Jellyfish (Chironex). More people are stung on the coast than in deeper water and one supposes that this is because more people swim on the beach than in open water. Tourist destinations with reported stings include Palm Island, Airlie Beach, the Whitsunday islands, Port Douglas, Mackay, Ingham, Cooktown, Lindeman Island, Great Keppel Island, Magnetic Island and Proserpine. Broome, Darwin and Arnhem Land also feature in reports.

In marked contrast to the Chironex with its immediate excruciating pain, the Irukandji sting is only moderately painful or irritating. The sting increases in intensity for a few minutes and then decreases over the next half hour. A red coloured 5–7 cm reaction surrounds the area of contact within five minutes. Small papules (pimples) appear and reach their maximum in about 20 minutes, before subsiding. A complex of typical systemic symptoms begins after a latency of about 30 minutes (range 5 to 120 minutes). The symptoms include severe abdominal pain (91%), back pain, limb or joint pain, nausea and vomiting, profuse sweating and agitation. Headache may be severe. The patient may not relate the symptoms to the local reaction due to the delay. Symptoms diminish or cease from 4 to 12 hours but complicating sequelae can develop.

Victims frequently require hospitalisation for management of severe pain and high blood pressure. A study in Cairns showed that 92% of patients had systemic signs of envenomation and 61% required intravenous narcotic analgesia as part of the treatment. An acute toxic cardiac failure is uncommon but not rare and requires admission to an intensive care unit. The majority of people are able to be discharged in 24 hours when symptoms have settled. A syndrome of malaise and muscle aches can persist for more than a week. Victims with an underlying heart condition or the elderly would be at significant risk of death or major morbidity from the Irukandji syndrome. The Irukandji syndrome has been misdiagnosed as a heart attack and as decompression illness.

As mentioned above, patients frequently need intravenous analgesia and management that is usually restricted to the hospital setting. One reviewer felt that the absence of deaths associated with the Irukandji syndrome was due to good in-hospital management of those envenomated. So where does this leave the sea kayaker? The literature indicates that a fit, young person would be very unlikely to die from a Carukia induced Irukandji syndrome but would benefit from formal medical attention. However, one can predict with complete confidence that anyone displaying typical symptoms of the Irukandji syndrome would be totally incapacitated from continuing any form of sea kayaking. Unsupported towing of a victim is unlikely to be successful and is generally contra-indicated anyway (see below). This leaves a rafted tow, best done with at least two un-envenomated people, one supporting, one towing. Coming ashore would have to be priority.


  1. Risk assessment based on location and season.
  2. Watch for discoid medusae (‘jelly button’, ‘hard water’, transparent coin-like animals) which indicate stinger potential.
  3. Wear protective clothing—wetsuits, body stockings of pantyhose (no excuse for wearing it on the south coast lads), lycra type suits (rashies). A mask would be a good idea to avoid eye stings.
  4. If you think someone has been stung, get out of the water.

First Aid – Valid For All Nasty Envenomations at Sea

  1. DR ABCDE;

    Danger: Protect yourself and the victim.

    Remove: Yourself and victim from the water. Remove tentacles if visible (use vinegar early if confirmed Chironex or Irukandji sting). Reassure the patient (and yourself).

    Airway, Breathing, Circulation: Assessed and maintained as per basic life support skills (you have all done your first aid course!).

    Disability: Watch for increasing incapacitation leading to patient danger.

    Exposure: Protect the patient from hypothermia, sunburn and dehydration.

  2. Once the victim is in their boat, stay rafted up and provide a supported tow to the nearest landing. Do not let the victim paddle. Do not leave the patient as they need constant reassessment and reassurance, impossible from 15 metres in front. I would not recommend a longer paddle to get to a more civilised landing. If the patient deteriorates on the water you have very limited ability to do much more than watch them die rafted up to your boat, although a burial at sea becomes an option (I think Matt Turner said an Inuit Classic looked like a coffin).
  3. If you have a mobile phone, two way transceiver or EPIRB then I would use them early. If you don’t then you are going to have to tough it out and it will be a pretty miserable and stressful time for all. Remember, the patient is unlikely to be capable of paddling for the next few days and early evacuation is better than late.

So there you have it. A small, invisible, near deadly creature with a time delay poison lurking in some of the best paddling areas in Australia, from the beaches to the reef. What are the chances of being stung by the Carukia barnesi (Irukandji)? Pretty small I suspect, about as small as being taken by a crocodile on a small deserted off-shore island… just check the odds with Arunas.


  • Further Understanding of and a New Treatment for Irukandji (Carukia Barnesi) Stings – Fenner, PJ et al. (Med J Aust 1986; 145: 569-574)
  • Irukandji syndrome: a risk for divers in tropical waters – Hadok, J. (Med J Aust 1997; 167: 649)
  • A Year’s experience of Irukandji envenomation in far north Queensland – Little, M et al. (Med J Aust 1998; 169: 638-641)
  • The Irukandji syndrome. A devastating syndrome caused by a north Australian jellyfish – Fenner, P et al (AustFam Physician 1999; 28(11): 1131-1137)
  • Dangerous Marine Creatures – Edmonds, C. Best Publishing Company, 1995