Irukandji syndrome: a widely misunderstood and poorly researched tropical marine envenoming.

Irukandji syndrome is a poorly defined set of symptoms that occur after envenoming by certain species of jellyfish, primarily cubozoans or 'box jellyfish'. Envenomed victims can show symptoms ranging from headaches, severe pain, nausea and vomiting to pulmonary oedema, cardiac failure and severe hypertension resulting in death. Historically, this syndrome appears to have been misdiagnosed and reported cases are undoubtedly a significant underestimation of the prevalence of this syndrome. The variation in symptoms has resulted in a myriad of treatments though none has been established as definitive. Effective pain relief with opioids is the most immediate priority. Although the annual numbers of envenomations are generally low, the associated financial costs of this envenomation may be comparatively high, with suggestions that it could run to millions of dollars per season in northern Australia alone. The syndrome has been well documented from many areas along the east coast of northern Australia, leading to the belief that it is an Australian oddity. However, with an increase in medical knowledge and improved diagnosis of the condition, it appears that envenomations causing Irukandji syndrome are an increasing marine problem worldwide.

Venom ontogeny, diet and morphology in Carukia barnesi, a species of Australian box jellyfish that causes Irukandji syndrome.

Venom profiles of two age groups of the medically important Australian box jellyfish Carukia barnesi [Southcott, R.V., 1967. Revision of some Carybdeidae (Scyphozoa, Cubomedusae), including description of jellyfish responsible for the 'Irukandji' syndrome. Aust. J. Zool. 15, 651-657] were compared. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis revealed differences in protein banding of tentacular venom between immature and mature animals. This correlates to a change in diet from invertebrate prey in immature C. barnesi medusae to vertebrate prey in mature medusae. Unlike other cubozoan studies, a change in venom did not equate to a change in nematocyst types or their relative frequencies. Additionally, comparison of tentacle structure and bell wart number showed developmental differences between the two age classes. Observations of prey capture in mature individuals and differences in bell warts between immature and mature medusae suggest different methods of prey capture are employed at different life stages of C. barnesi.