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The Irukandji syndrome - an introduction
In 1943, whilst serving with troops stationed in the Cairns, north Queensland area, Dr Ron Southcott first described a strange syndrome that occurred in a group of troops who went swimming in the tropical seas. This syndrome presented with a minor skin sting but was followed approximately 30 minutes later by a bizarre set of distressing systemic symptoms. He called these Type "A" stingings to distinguish between another group of jellyfish stings, which caused severe and instant local skin pain (Type "B" stings, later identified as being due to the Chironex box jellyfish). ¹
Still unaware of the cause, in 1952 Flecker named this set of delayed systemic symptoms the "Irukandji syndrome", after a local aboriginal tribe in the Palm Cove, Cairns area, where most of these envenomations occurred. ² However, it was not until 1966 that Dr Jack Barnes, using some amazing detective work, captured a small (1.5-2.0cm bell diameter) carybdeid (box jellyfish with just one tentacle in each corner). He then stung himself, his son and a volunteer lifesaver to see if it caused the Irukandji syndrome. ³ All three ended up in the Cairns Base Hospital Intensive Care Unit with the typical severe systemic symptoms of the Irukandji syndrome described below (this is not a recommended procedure!). Southcott later named the jellyfish⁴ Carukia barnesi after its intrepid discoverer.
The "slang" name of Irukandji has previously been reserved for Carukia barnesi, but is now increasingly used for any jellyfish causing this bizarre syndrome. In this article the term "Irukandji" is used for any small carybdeid (small box jellyfish) causing the set of systemic symptoms known as the Irukandji syndrome (described below). However, it must be remembered that no other small carybdeid jellyfish has even been proven to cause this syndrome, even if it appears it may.
Since this early research, severe systemic symptoms including cases of toxic heart failure have been described.^{5 6 7 8} However, this year some 30% of cases reported to the author's sting database^* have had some degree of heart failure, with some cases being severe enough to warrant admission and exhaustive and complex treatment for up to 8 days for severe toxic heart failure, and lung complications. In addition to this there have been further bizarre symptoms reported which are unexplainable at the current time, and which are described below.
A recent 1998 report of 60 Irukandji stings from Cairns⁹ did suggest that the Irukandji syndrome was mild and had few severe systemic effects, with the majority of patients being discharged home after several hours monitoring in a specialised "observation ward", and without the need for admission. A criteria for early discharge was a requirement for less than 2mg/kg of pethidine. However, the authors are aware of two cases where heart failure developed in patients who required less than this amount of pethidine.* It may be more appropriate to use a lower dose of pethidine (such as 1mg/kg) and/or include other criteria such as breathlessness. Also, two of their cases had heart failure and did require admission to a critical care unit. This article included data from the Cairns Region only, where most of the stings occurred inside a "stinger-resistant enclosure".
Stinger resistant enclosures are nets of small (approximately 20mm diagonally) mesh, suspended from floating pontoons. They provide an area for swimming in the sea that effectively precludes Chironex box jellyfish. However, the small mesh nets do allow the entry of smaller jellyfish, including the Irukandji. As the Cairns group describes few cases being admitted to Intensive Care facilities, with the majority of patients sent home, and other