Biology and ecology of Irukandji jellyfish (Cnidaria: Cubozoa).

Irukandji stings are a leading occupational health and safety issue for marine industries in tropical Australia and an emerging problem elsewhere in the Indo-Pacific and Caribbean. Their mild initial sting frequently results in debilitating illness, involving signs of sympathetic excess including excruciating pain, sweating, nausea and vomiting, hypertension and a feeling of impending doom; some cases also experience acute heart failure and pulmonary oedema. These jellyfish are typically small and nearly invisible, and their infestations are generally mysterious, making them scary to the general public, irresistible to the media, and disastrous for tourism. Research into these fascinating species has been largely driven by the medical profession and focused on treatment. Biological and ecological information is surprisingly sparse, and is scattered through grey literature or buried in dispersed publications, hampering understanding. Given that long-term climate forecasts tend toward conditions favourable to jellyfish ecology, that long-term legal forecasts tend toward increasing duty-of-care obligations, and that bioprospecting opportunities exist in the powerful Irukandji toxins, there is a clear need for information to help inform global research and robust management solutions. We synthesise and contextualise available information on Irukandji taxonomy, phylogeny, reproduction, vision, behaviour, feeding, distribution, seasonality, toxins, and safety. Despite Australia dominating the research in this area, there are probably well over 25 species worldwide that cause the syndrome and it is an understudied problem in the developing world. Major gaps in knowledge are identified for future research: our lack of clarity on the socio-economic impacts, and our need for time series and spatial surveys of the species, make this field particularly enticing.

Fatal and severe box jellyfish stings, including Irukandji stings, in Malaysia, 2000-2010.

BACKGROUND: Jellyfish are a common cause of injury throughout the world, with fatalities and severe systemic events not uncommon after tropical stings. The internet is a recent innovation to gain information on real-time health issues of travel destinations, including Southeast Asia. METHODS: We applied the model of internet-based retrospective health data aggregation, through the Divers Alert Network Asia-Pacific (DAN AP), together with more conventional methods of literature and media searches, to document the health significance, and clinical spectrum, of box jellyfish stings in Malaysia for the period January 1, 2000 to July 30, 2010. RESULTS: Three fatalities, consistent with chirodropid envenomation, were identified for the period-all tourists to Malaysia. Non-fatal chirodropid stings were also documented. During 2010, seven cases consistent with moderately severe Irukandji syndrome were reported to DAN and two representative cases are discussed here. Photographs of chirodropid (multi-tentacled), carybdeid (four-tentacled) box jellyfish, and of severe sting lesions were also submitted to DAN during this period. CONCLUSIONS: This study suggests that the frequency and severity of jellyfish stings affecting tourists in Southeast Asia have been significantly underestimated. Severe and fatal cases of chirodropid-type stings occur in coastal waters off Peninsular Malaysia and Sabah, Borneo. Indeed, the first Malaysian cases consistent with Irukandji-like syndrome are reported here. Reports to DAN, a provider of emergency advice to divers, offer one method to address the historic lack of formalized reporting mechanisms for such events, for photo-documentation of the possible culprit species and treatment advice. The application of marine stinger prevention and treatment principles throughout the region may help reduce the incidence and severity of such stings. Meanwhile travelers and their medical advisors should be aware of the hazards of these stings throughout the Asia-Pacific.

Severe Irukandji-like jellyfish stings in Thai waters.

Over recent years, there have been more widely-reported sightings of chirodropids and carybdeids in Thailand. There has also been an increased awareness and documentation of fatal and severe non-fatal jellyfish stings occurring in Thai waters. Although the victims are usually swimming or wading in shallow water, divers are also at risk. Despite generally wearing some protective coverings while diving in the tropics, parts of a diver's body often remain exposed and divers can and do sustain severe and/or life-threatening jellyfish stings. In December 2007 and January 2008, two serious cases of envenomation in divers in Thailand were reported to Divers Alert Network Asia-Pacific (DAN AP). Both of these victims displayed some typical symptoms of an irukandji-like syndrome. Similar to Australia, appropriate measures need to be taken by the Thai authorities to warn locals and tourists alike of the possible presence of dangerous jellyfish, and suitable prevention and management strategies need to be established and implemented to minimise morbidity and mortality.

Cardiovascular actions of the venom from the Irukandji (Carukia barnesi) jellyfish: effects in human, rat and guinea-pig tissues in vitro and in pigs in vitro.

1. We have investigated the cardiovascular pharmacology of the crude venom extract (CVE) from the potentially lethal, very small carybdeid jellyfish Carukia barnesi, in rat, guinea-pig and human isolated tissues and anaesthetized piglets. 2. In rat and guinea-pig isolated right atria, CVE (0.1-10 microg/mL) caused tachycardia in the presence of atropine (1 micromol/L), a response almost completely abolished by pretreatment with tetrodotoxin (TTX; 0.1 micromol/L). In paced left atria from guinea-pig or rat, CVE (0.1-3 microg/mL) caused a positive inotropic response in the presence of atropine (1 micromol/L). 3. In rat mesenteric small arteries, CVE (0.1-30 microg/mL) caused concentration-dependent contractions that were unaffected by 0.1 micromol/L TTX, 0.3 micromol/L prazosin or 0.1 micromol/L omega-conotoxin GVIA. 4. Neither the rat right atria tachycardic response nor the contraction of rat mesenteric arteries to CVE were affected by the presence of box jellyfish (Chironex fleckeri) antivenom (92.6 units/mL). 5. In human isolated driven right atrial trabeculae muscle strips, CVE (10 microg/mL) tended to cause an initial fall, followed by a more sustained increase, in contractile force. In the presence of atropine (1 micromol/L), CVE only caused a positive inotropic response. In separate experiments in the presence of propranolol (0.2 micromol/L), the negative inotropic effect of CVE was enhanced, whereas the positive inotropic response was markedly decreased. 6. In anaesthetized piglets, CVE (67 microg/kg, i.v.) caused sustained tachycardia and systemic and pulmonary hypertension. Venous blood samples demonstrated a marked elevation in circulating levels of noradrenaline and adrenaline. 7. We conclude that C. barnesi venom may contain a neural sodium channel activator (blocked by TTX) that, in isolated atrial tissue (and in vivo), causes the release of transmitter (and circulating) catecholamines. The venom may also contain a 'direct' vasoconstrictor component. These observations explain, at least in part, the clinical features of the potentially deadly Irukandji syndrome.

Health advice obtained by tourists travelling to Magnetic Island: a risk area for 'Irukandji' jellyfish in North Queensland, Australia.

BACKGROUND: Little is known about the travel health advice obtained by tourists travelling to Magnetic Island, which is a known risk area for the potentially fatal 'Irukandji' jellyfish on the Great Barrier Reef coast of north Queensland, Australia. METHODS: Structured interviews were conducted with 208 ferry passengers (93% response) travelling between Townsville (Latitude 19 degrees S) and Magnetic Island. RESULTS: Less than half of the international tourists (21, 46%) had obtained travel health advice before coming to north Queensland, although they were significantly more likely to have done so than domestic tourists (p<0.001). Travel health advice obtained by international tourists was sourced mainly from their general practitioner (8, 50%) or from a guidebook (6, 38%). Eighty-eight percent of north Queensland residents, 70% of domestic tourists, and 34% of international tourists knew what an Irukandji jellyfish was (p<0.001), although this was not associated with having obtained travel health advice. For those passengers returning from the Island, 8 (44%) domestic tourists and 4 (35%) international tourists recalled seeing some information on the Island that improved their knowledge about Irukandji jellyfish. Most of the international tourists travelled to north Queensland by bus (30, 65%), while most domestic tourists arrived by private car (12, 40%) or plane (10, 33%). CONCLUSIONS: Only a small proportion of international tourists knew about Irukandji jellyfish and most tourists had not received travel health advice. The majority of tourists had not received further information about Irukandji jellyfish risk whilst on the island. All travellers to popular north Queensland tourist areas need travel health advice, which includes advice on avoiding contact with Irukandji and Chironex box jellyfish. Health promotion campaigns directed at providing this advice need to be aware that most tourists to north Queensland arrive by bus or car and the only 'shared' vehicle, at least to Magnetic Island, is the passenger ferry.

Phospholipase A2 in cnidaria.

Phospholipase A2 (PLA2) is an enzyme present in snake and other venoms and body fluids. We measured PLA2 catalytic activity in tissue homogenates of 22 species representing the classes Anthozoa, Hydrozoa, Scyphozoa and Cubozoa of the phylum Cnidaria. High PLA2 levels were found in the hydrozoan fire coral Millepora sp. (median 735 U/g protein) and the stony coral Pocillopora damicornis (693 U/g) that cause skin irritation upon contact. High levels of PLA2 activity were also found in the acontia of the sea anemone Adamsia carciniopados (293 U/g). Acontia are long threads containing nematocysts and are used in defense and aggression by the animal. Tentacles of scyphozoan and cubozoan species had high PLA2 activity levels: those of the multitentacled box jellyfish Chironex fleckeri contained 184 U/g PLA2 activity. The functions of cnidarian PLA2 may include roles in the capture and digestion of prey and defense of the animal. The current observations support the idea that cnidarian PLA2 may participate in the sting site irritation and systemic envenomation syndrome resulting from contact with cnidarians.

Reported knowledge, perceptions, and behavior of tourists and North Queensland residents at risk of contact with jellyfish that cause the "Irukandji syndrome".

OBJECTIVE: To determine the knowledge, beliefs, and behavior of local residents and visitors to North Queensland who may be at risk of contact with "Irukandji" jellyfish. METHODS: Structured interviews were conducted with 208 ferry passengers (92.9% response) traveling between Magnetic Island and Townsville (19 degrees S). RESULTS: A total of 88.1% of the locals, 69.8% of the domestic tourists, and 34% of the international tourists knew what an Irukandji was (P < .001). Half of the international tourists, 20% of the domestic tourists, and 3.9% of the locals with this knowledge incorrectly assumed it was safe to swim inside stinger-resistant enclosures or were unsure (P < .001). Visitors to Magnetic Island who had swum or intended to swim in the sea (47%) knew less about Irukandji than other visitors (P = .05). Only 42.3% of the respondents realized that Irukandji posed a risk to swimmers on the outer reefs, and only 33.1% knew that Irukandji were also found outside North Queensland. CONCLUSIONS: International tourists had little knowledge about Irukandji. Thus, accurate educational messages may need to be targeted at this group. Offshore water sport and reef tour operators should be encouraged to provide clients with protective clothing to minimize the risk of stings. A coordinated educational response across northern Australia may be necessary to inform the public about both the box jellyfish (Chironex fleckeri) and Irukandji.

Fatal envenomation by jellyfish causing Irukandji syndrome.

We report the first of two recent deaths from Irukandji syndrome. A 58-year-old male tourist was stung on the face and chest by an unidentified jellyfish in shallow water off the Whitsunday Islands, Queensland. He developed muscle cramps, sweating, anxiety, nausea and hypertension, and died 30 hours later from intracerebral haemorrhage.