Most stings occur during the summer wet season in October–May in North Queensland, with different seasonal patterns elsewhere. Because jellyfish are very small, the venom is only injected through the tips of the nematocysts rather than the entire lengths; as a result the sting may barely be noticed at first. It has been described as feeling like little more than a mosquito bite. The symptoms, however, gradually become apparent and then more and more intense in the subsequent 5 to 120 minutes. Irukandji syndrome includes an array of systemic symptoms, including severe headache, backache, muscle pains, chest and abdominal pain, nausea and vomiting, sweating, anxiety, hypertension, tachycardia and pulmonary edema. Symptoms generally improve in four to 30 hours, but may take up to two weeks to resolve completely.
Toxicity
When properly treated, a single sting is almost never fatal; however, two people in Australia are believed to have died from Irukandji stings, which has greatly increased public awareness of Irukandji syndrome. It is unknown how many other deaths from Irukandji syndrome have been wrongly attributed to other causes.
Similar to other box jellyfish stings, first aid consists of flushing the area with vinegar to neutralize the tentacle stinging apparatus. As no antivenom is available, treatment is largely supportive, with analgesia being the mainstay of management. Nitroglycerin, a common drug used for cardiac conditions, is utilised by medical personnel to minimise the risk of pulmonary edema and to reduce hypertension. Antihistamines may be of benefit for pain relief, but most cases require intravenousopioid analgesia. Fentanyl or morphine are usually chosen. Pethidine should be avoided, as large doses are often required for pain relief and in this situation significant adverse effects from the pethidine metabolite norpethidine may occur. Magnesium sulfate has been proposed as a treatment for Irukandji syndrome after being apparently successfully used in one case. Early evidence suggested a benefit; however, according to a later report, a series of three patients failed to show any improvement with magnesium; the author reiterated the experimental status of this treatment. Some preliminary laboratory experiments using the venom extracted from Malo maxima on rat cardiovascular tissue in vitro has suggested that magnesium does in fact block many of the actions of this venom.
In 1964 Jack Barnes confirmed the cause of the syndrome was a sting from a small box jellyfish: the Irukandji jellyfish, which can fire venom-filled stingers out of its body and into passing victims. To prove that the jellyfish was the cause of the syndrome, he captured one and deliberately stung himself while his son Nick and a local lifeguard then observed the resulting symptoms. Other cubozoans possibly can cause Irukandji syndrome; those positively identified include Carukia barnesi, Alatina cf. mordens, Alatina alata, Malo maximus, Malo kingi, Carybdea xaymacana, Keesingia gigas, an as-yet unnamed "fire jelly", and another unnamed species.
Media portrayals
A 2005 Discovery Channel program, Killer Jellyfish, portrayed the severity of the pain from an Irukandji jellyfish sting when two Australian researchers were stung. Another program aired on the Discovery Channel, Stings, Fangs and Spines, featured a 20-minute spot on Irukandji syndrome. In the segment, a young Australian woman was stung and developed a severe case. A 2007 fictional Sea Patrol episode involves two crew members of HMAS Hammersley being stung by an Irukandji jellyfish. On the television program Super Animal, a woman compared her experience with Irukandji syndrome to the pain from childbirth. Steve Backshall reports with accounts from victims of Irukandji stings on his ITV wildlife series Fierce in 2016.
