Irukandji

Carukia barnesi (the Irukandji) is a small jellyfish (~2cm diameter bell) whose sting causes an unusual and dramatic syndrome. Unlike Chironex fleckeri, Irukandji are found mostly in the deeper waters of the reefs in northern Australia, especially north Queensland. Although they may be swept inshore by prevailing currents. Divers and snorkellers are particularly at risk. Stings have been recorded from Childers to Broome, and a similar syndrome has been described elsewhere in the Pacific. Many people have been affected, including several hundred in north Queensland in the summer of 1991/92 and 2001/02.

Every summer, more than sixty people are hospitalized with this potentially fatal syndrome. The sting itself is only moderately painful, with little associated tissue damage. But approximately 30 minutes later the patient develops a complex of systemic symptoms including severe back and abdominal pain, limb or joint pain, nausea and vomiting, profuse sweating and agitation. They may also experience numbness or paraesthesia. Hypertension and tachycardia are frequently seen, and are thought to be related to catecholamine release. Victims frequently require hospitalisation for analgesia and sometimes intravenous antihypertensive therapy; alpha-blocking agents such as phentolamine have been used for this purpose. Supraventricular tachycardia and transient dilated cardiomyopathy have been reported following irukandji stings, and it has been suggested that serial echocardiography be performed to monitor the progress of severely affected patients. Analgesia is usually required, and may need to be given intravenously when pain is severe. First aid consists of analgesia and reassurance. The role of vinegar to inactivate undischarged nematocysts remains uncertain, with initial work proving inconclusive. No definitive treatment is currently available for the Irukandji syndrome, although the drug magnesium sulphate is undergoing clinical trials. The Australian Venom Research Unit is currently involved in research to develop an antivenom to treat this envenomation.