College of Marine and Environmental Sciences, James Cook University, Townsville City QLD 4811, AUSTRALIA.
Coming into contact with particular jellyfish species causes envenomation, and can trigger a range of debilitating, even fatal, set of symptoms called Irukandji Syndrome. Despite the risk to human health, potential losses in tourist revenue, and direct, substantial costs of treatment, there is confusion in the diagnosis and treatment of Irukandji Syndrome, and major gaps in our knowledge about the fundamental biology and ecology of the animals that cause it. This project examined the scope of Irukandji Syndrome and scrutinized the current ideas in relation to its distribution, definition and treatment. Focusing on one species known to cause Irukandji Syndrome, I examined the variation in morphology, reproduction, development and venom composition between two geographically distant populations (Australia and Hawaii) and explore whether Irukandji Syndrome diagnoses and treatments are likely to be affected by intraspecies variations in ecology.
My research into the occurrence of this syndrome identified that there is no encompassing diagnostic tool, making identification and accurate recording of this syndrome extremely difficult. I compiled a retrospective analysis of historical sting records, which represents the largest such database ever examined to date. From these data, I found that overwhelming, predominance of pain is a main symptom of Irukandji stings, and in many cases this can be the only symptom displayed. Notably, this illustrates that the most current definition for Irukandji Syndrome diagnosis as reported in the literature is not adequate, as an overwhelming 74% of these patients observed would not fit these guidelines (of experiencing at least three or more systemic symptoms). Based on my research, I propose a new diagnostic tool in order to provide a more encompassing definition of this syndrome and have named this Irukandji Syndrome Complex. I believe that this should be adopted on a global scale and in doing so the full distribution of Irukandji Syndrome Complex stings will be revealed.
While examining the efficacy of different treatments administered for Irukandji Syndrome, I found that the amount of opiates required for treatment was indicative of sting severity and there is evidence to suggest that stings occurring out on the reef locations have a higher probability of resulting in a more severe sting with an increased potential for cardiac damage presenting in this region.
There is evidence that Irukandji Syndrome poses an increasing risk to human health through temporal extension of high-risk ‘stinger’ seasons on a local scale, with stings presenting over a significantly greater length of the year over the last 65 years. There has been a reduction in the proportion of stings that occur from beach locations in the Cairns region and this appears to be correlated with the change in Surf Lifesaving protocols for this area.
One species that is known to cause Irukandji Syndrome, Alatina moseri, occurs in two geographically distant populations: in the waters off Australia and Hawaii. To learn more about their general ecology, and whether there are intraspecific variations that may be relevant to the prevention, diagnosis or treatment of Irukandji Syndrome caused by this species, I examined both populations. There is evidence that these populations share similar morphology, though the Australian population was typically larger in size, and both have strong reproductive periodicity, with sexually mature, actively spawning animals appearing for circumlunar aggregations. However, analysis of the venom components present in this species showed distinct variation both geographically and temporally with a change in both number and frequency of proteins present. This highlights the potential for one of the variations in Irukandji Syndrome symptoms and severity I observed to result from intraspecific venom variation. The periodic aggregations of these animals do however make their appearance highly predictable and therefore it may be possible to prevent the number of envenomations by redirecting marine users from higher risk waters at these times to allow for this occurrence and reduce sting potential.
Lastly the spawning populations encountered allowed for insight into the early life history of these animals that has not previously been described. My observations of A. moseri’s development from fertilized eggs right through to metamorphosed medusa supports recent research that these two populations are taxonomically one species, despite variations displayed in their venom composition. Additionally it gives a timeline and some environmental parameters for the development from the sessile polyp to active medusa stage, which is essential for further understanding of the overall biology of this otherwise cryptic, but medically relevant species.
In summary, this study has sought to advance our understanding of a debilitating condition that occurs globally, and may be expanding in range. By examining the medical diagnostic characteristics of Irukandji Syndrome, and clarifying these by bringing together all the relevant case studies, analysing the historic presentations to look for change over time, and analysing the ecology and venom composition of a species known to cause of Irukandji Syndrome, this research has provided key information that will help to better prevent, diagnose and treat it this debilitating disease.