eMJA: Little & Mulcahy, A year's experience of Irukandji envenomation in far north Queensland

Bites and Stings

A year's experience of Irukandji envenomation in far north Queensland

Mark Little and Richard F Mulcahy

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MJA 1998; 169: 638-641

Envenomation by the Irukandji jellyfish (Carukia barnesi) can result in an array of systemic symptoms known as Irukandji syndrome. In 1996, 62 people presented to Cairns emergency departments with Irukandji envenomation: 57 developed systemic symptoms, and 38 required parenteral narcotics. All patients were discharged home within 24.5 hours, except for two who required high-dependence care for pulmonary oedema. Patients were more likely to be stung on hotter days, with lower-than-average rainfall in the past seven days, and with winds from the north, but less-than-average wind speed. We offer a protocol for treating patients with Irukandji envenomation.

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Introduction - Methods - Results - Discussion - Conclusion - Acknowledgements - References - Authors' details
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Introduction

Very little is known about the Irukandji jellyfish (Carukia barnesi), which is responsible for a substantial number of envenomations in far north Queensland, and other parts of northern Australia, each year. It was first named by Flecker in 1952, after an Aboriginal tribe that lived in the Cairns region.¹ However, it was Barnes who, in 1964, was finally able to identify the jellyfish and demonstrate that it produced the Irukandji syndrome.² The jellyfish is small (its bell is up to 2.5 cm across), but the tentacles may be up to one metre long.³ It is rarely seen before envenomation.⁴ The stinging apparatus, located along the tentacles, is called the nematocyst, and contains what has been likened to a coiled "harpoon".^5,6 On stimulation, the nematocyst bursts open discharging the harpoon.

Envenomation by the Irukandji jellyfish can lead to an array of systemic symptoms known as the Irukandji syndrome. Symptoms include severe backache, muscle pains, chest and abdominal pain, nausea and vomiting, headache, sweating, and (rarely) pulmonary oedema.^7-9 No antivenom exists.

The Irukandji jellyfish

Other than the observations of Flecker and Barnes, many of the published medical reports are anecdotal, discussing small numbers of cases.^4,7-11 In view of the large number of envenomations seen in Cairns and the fact that this jellyfish was first identified in Cairns, we reviewed all cases of Irukandji envenomations presenting to hospital emergency departments in Cairns in 1996. We have previously reported 30 of these cases (patients who presented to Cairns Base Hospital in December 1996).⁵ Our aim was to reproduce the observations of Flecker and Barnes, identify where and when people would be more likely to be envenomed, and to develop a protocol for their management.

Methods

The Cairns Base Hospital Emergency Department and the Calvary Emergency Centre (a private hospital) were the only emergency departments in Cairns in 1996. Both maintain a database of all patients presenting, and these databases were searched to identify all patients with possible marine envenomation. We reviewed the charts and included in the study patients who had at least two symptoms or signs of Irukandji envenomation.^1,2

The Bureau of Meteorology in Cairns supplied daily weather information for 1996. Clinical and weather data were collated. All data were analysed using SPSS.¹²

Results

In 1996, 62 patients with Irukandji envenomation were seen by the two emergency departments. The patients ranged in age from 18 months to 56 years; 23 (37%) were younger than 14 years. Twenty-nine (47%) were male.

Box 1 shows the monthly distribution of the cases. No patients with Irukandji envenomation presented to either emergency department between 18 May and 11 October.

Box 1

Forty-seven (76%) patients were stung at coastal locations, seven (11%) were stung on the Reef, and five (8%) on the islands just off Cairns (Box 2). Of the 34 patients seen in December 1996, 30 (88%) were stung at coastal locations, compared with 17 of 26 (65%) for the period from January to May. Thirty-nine patients (63%) were stung while swimming inside stinger net enclosures on the beaches.

Boxes 2 & 3

Signs and symptoms

Fifty-seven of the 62 (92%) patients had systemic signs and/or symptoms of envenomation, and 38 (61%) required parenteral narcotics. Two patients developed pulmonary oedema. The most common signs and symptoms are listed in Box 3.

Treatment

Vinegar: For nine patients, the use of vinegar was not recorded. Of the remaining 53 patients, 43 (81%) had vinegar applied. We saw no adverse effect from the use of vinegar, with no worsening of symptoms.

Opiate analgesia: Thirty-eight (61%) patients received opiates: 30 pethidine, two morphine, and six both morphine and pethidine. Twenty-four adults received pethidine; 16 required 100 mg or more, with one patient receiving 750 mg of pethidine over 10 hours. One adult received a dose of 60 mg morphine in 12 hours.

Fourteen (61%) children required opiates: seven received 2 mg/kg or more of pethidine, with two receiving more than 5 mg/kg of pethidine, both over 14 hours.

Promethazine: Promethazine was administered to 16 patients, primarily as an antiemetic. There was a significant reduction in the amount of pethidine used when promethazine was administered to adults (univariate analysis of variance, F = 4.811; df = 1, 58; P = 0.032). On average, 40 mg of pethidine was administered to patients who received promethazine, compared with 140 mg to patients who did not receive promethazine.

Retrievals

Six (9.7%) patients required aeromedical transfer to Cairns Base Hospital, five by Cairmed (the helicopter emergency retrieval service staffed by the Emergency Department), and one by the Royal Flying Doctor Service.

Outcome

Of the 62 patients treated, 28 were discharged home within six hours of envenomation with minimal or no symptoms. One child, who initially received more than 5 mg/kg of pethidine, re-presented with pain, hypertension and sweating five hours after being discharged. Thirty-five (56%) patients were admitted to hospital (Box 4).

Box 4

Weather

Fifty-seven (92%) patients were stung on days hotter than the average for the month when the sting occurred. Forty-three (69%) patients were stung on days with more hours of sunshine than average. Fifty-four (87%) patients were stung on days when 5 mm or less of rain fell during the day, and 47 (76%) were stung when less than the average amount of rain had fallen in the past seven days. Forty-seven (76%) patients were stung on days when the wind was between the north-north-west (NNW) and north-north-east (NNE). During 1996, the prevailing wind was between the NNE and NNW for 99 of 366 days (27% of the time). Using backwise multiple regression analysis, weather conditions that were significantly associated with Irukandji stinging were temperature hotter than average, less-than-average rainfall in the past seven days, and wind speed less than average (F = 7.919; df = 36, 214; P < 0.001).

Discussion

In 1996 we saw 62 cases of Irukandji envenomation, with two patients developing pulmonary oedema. To our knowledge, this is the largest number of Irukandji envenomations reported from a single location in one year. During this period we treated only two patients for minor box jellyfish (Chironex fleckeri) envenomations.

We have been able to confirm many of Barnes's observations.² There appears to be a brief period in the year when there are a large number of envenomations, usually associated with northerly winds.² Forty-seven (76%) of our patients were stung on days when the wind was between the NNW and NNE. In our study, 35 (56%) patients were stung between 30 November and 19 December 1996. Like Barnes, we found the most frequent location to be stung was Palm Cove (17/62; 27%), about 25 km north of Cairns.

The reason the Irukandji has this swarm period, which was also described by Flecker¹ and Barnes,² is not clear. We believe that the Irukandji may originate from the coastal region. There is a higher proportion of people stung on the Reef between January and May (9/26; 33%) compared with October to December (3/37; 8%). We believe the "swarm" occurs because the Irukandji are either breeding or pursuing food, before moving to open water later in the season.

In Cairns, the risk from jellyfish stings in the "wet" season (November-May) is well known, and stinger-resistant swimming enclosures are placed at all main beaches. The holes in the nets are 25 mm x 25 mm. Previous reports^5,8,10 have noted people being stung within these enclosures. In our study, 39 (63%) patients were stung within the stinger-netted areas. Clearly, the nets do not offer protection against the Irukandji, which has a bell size up to 25 mm. Most people we spoke to while they or their children were being treated believed that the netted area protected against all jellyfish. All beaches in the Cairns region have the same warning message, which we believe to be inadequate. The second paragraph of the warning message states: The stinger net enclosure is designed to afford a reasonable measure of protection from marine stingers. We believe better warnings need to be placed on all beaches where a stinger net enclosure exists, especially when the conditions are favourable for the "swarm" of Irukandji. As six people were envenomed at the water's edge, the warning needs to include this risk.

Two (3%) patients developed pulmonary oedema, suggesting that the frequency of pulmonary oedema may be more common than previously realised. Pulmonary oedema is a documented complication of Irukandji envenomation,^5,8-10,13 usually occurring 10-12 hours after envenomation. In both our patients with pulmonary oedema, echocardiography showed reduced left ventricular function, as demonstrated in previous studies.^9,13 The toxin may have a direct myocardial depressant action. Others have hypothesised that capillary leak is secondary to catecholamine release.¹⁰

Concerns have been raised about the effectiveness of vinegar,¹⁴ and whether or not all the nematocysts are inactivated. We found that vinegar caused no adverse reaction in any patient. Vinegar has been shown to inactivate the nematocysts of other jellyfish (eg, the box jellyfish), and the nematocysts of the Irukandji have been shown to be inactivated in vitro by vinegar.⁸ Accordingly, we continue to advocate its use.

The use of compression bandages is currently recommended by some,¹³ and appears on posters produced by Queensland Surf Rescue at beaches in the Cairns region. Only one patient in our trial had a bandage applied. Like Holmes,³ we have concerns regarding the use of bandages. Firstly, if there are nematocysts remaining on the skin, direct pressure may cause more of them to fire and worsen the envenomation. Secondly, the toxin may reach the systemic circulation by the lymphatics, as there is usually a 30-60-minute delay between the sting and systemic symptoms developing.¹⁵ Application of a pressure bandage may delay the venom reaching the systemic circulation. However, its removal may result in the patient receiving a sudden bolus of toxin.

Pethidine has been recommended in preference to morphine.² However, we are concerned at the dose of pethidine some of our patients required. Pethidine has direct myocardial and respiratory depressant effects and has a toxic metabolite (norpethidine). As the Irukandji toxin may exhibit a direct myocardial depressant effect, a large dose of pethidine may worsen the cardiovascular function of the patient. We feel that, if there is ongoing pain, fentanyl would be more appropriate. Fentanyl has almost pure narcotic receptor action with no cardiac depression and has no toxic metabolite.

We found promethazine was of benefit in treating pain. Promethazine, an antihistamine, also blocks a variety of receptors, including muscarinic, a-adrenergic and serotonin receptors. It has local anaesthetic properties and is an effective antiemetic. Whether it works in treating Irukandji syndrome by blocking one of the above-mentioned receptors or whether it acts to potentiate the effect of the opiate is unclear.

Reassuringly, 27 patients were discharged after an average stay of 2.1 hours in the emergency department, and did not return with further symptoms. Only one child re-presented. This patient had received a total of 5 mg/kg of pethidine in the six hours after envenomation, and clearly should have been admitted then. All other patients who received more than 2 mg/kg pethidine were admitted. They were discharged when they were asymptomatic or had had minimal symptoms for six hours. Other than the two patients admitted to the high-dependence areas, all were discharged within 24.5 hours.

We have designed a management protocol for Irukandji envenomation (Box 5). If patients have no systemic symptoms during the first two hours after presentation they may be discharged home. If there is any opiate requirement, they need to be admitted until they have remained symptom free, with no analgesia requirement, for six hours. We suspect that pulmonary oedema is under-recognised. Therefore, any patient who has more than 2 mg/kg of pethidine (suggesting significant envenomation) requires investigations such as chest x-ray and electrocardiogram. If available, echocardiography, which is more accurate in diagnosing ventricular dysfunction, should be performed. Fentanyl should be used for further analgesia.

Box 5

Conclusion

Very little is known about the Irukandji, its life cycle or its toxins. We have demonstrated that it causes significant morbidity, with potentially life-threatening symptoms. In view of the varied nature of our patients' presentations, and that 27 (44%) patients were discharged home within 2.1 hours, we suspect, like Barnes,¹⁵ that there may be more than one type of jellyfish responsible for the Irukandji syndrome. Irukandji presents a significant workload to the hospital emergency departments in presentations, retrievals and admissions. We have developed a protocol for managing patients; however, we would like an antivenom to be developed.

Acknowledgements

We are grateful for the assistance of the Bureau of Meteorology Office in Cairns. We are also grateful for the helpful advice and assistance with the statistical analysis of the data by Dr Jamie Seymour of James Cook University (Cairns campus).

References

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Barnes JH. Cause and effect in Irukandji stingings. Med J Aust 1964; 1: 897-904.
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Fenner PJ, Burnett JW, Colquhon DM, et al. The "Irukandji Syndrome" and acute pulmonary oedema. Med J Aust 1988; 149: 150-156.
Martin JC, Audley I. Cardiac failure following Irukandji envenomation. Med J Aust 1990; 153: 164-166.
Fenner PJ, Heazlewood RJ. Papilloedema and coma in a child: undescribed symptoms of the "Irukandji" syndrome. Med J Aust 1997; 167: 650.
SPSS for Windows [computer program]. Version 6.0. Chicago, Ill: SPSS Inc, 1992.
Williamson JA, Fenner PJ, Burnett JW, Rifkin JF, editors. Venomous and poisonous marine animals. Sydney: University of New South Wales Press, 1996: 246-255.
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Kinsey B, editor. More Barnes on Box jellyfish. Townsville: James Cook University of North Queensland, 1988; 33-107.

Authors' details

Department of Emergency Medicine, Cairns Base Hospital, QLD.
Mark Little, DTM&H(London), FACEM, Senior Medical Officer;
Richard F Mulcahy, MB, BCh, BAO, Registrar.

Reprints will not be available from the authors.
Correspondence: Dr M Little, Senior Medical Officer, Department of Emergency Medicine, Cairns Base Hospital, PO Box 902, Cairns, QLD 4870.
Email: mulcahysATinternetnorth.com.au

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