«Mar. Drugs 2013, 11, 523-550; doi:10.3390/md11020523 OPEN ACCESS Marine Drugs ISSN 1660-3397 Review Jellyfish Stings ...»
Mar. Drugs 2013, 11, 523-550; doi:10.3390/md11020523
Jellyfish Stings and Their Management: A Review
Luca Cegolon 1,2,*, William C. Heymann 3, John H. Lange 4 and Giuseppe Mastrangelo 1
Department of Molecular Medicine, Padua University, Padua 35128, Italy;
E-Mail: firstname.lastname@example.org 2 School of Public Health, Imperial College London, St. Mary’s Campus, London WC2 1PG, UK 3 Sarasota County Health Department, Sarasota, FL 34237, USA;
E-Mail: email@example.com 4 Envirosafe Training and Consultants, 2366 Golden Mile Highway, Pittsburgh, PA 15239, USA;
E-Mail: firstname.lastname@example.org * Author to whom correspondence should be addressed; E-Mail: email@example.com;
Tel.: +39-049-8212543; Fax: +39-049-8212542.
Received: 28 November 2012; in revised form: 22 December 2012 / Accepted: 25 January 2013 / Published: 22 February 2013 Abstract: Jellyfish (cnidarians) have a worldwide distribution. Despite most being harmless, some species may cause local and also systemic reactions. Treatment of jellyfish envenomation is directed at: alleviating the local effects of venom, preventing further nematocyst discharges and controlling systemic reactions, including shock. In severe cases, the most important step is stabilizing and maintaining vital functions. With some differences between species, there seems to be evidence and consensus on oral/topical analgesics, hot water and ice packs as effective painkillers and on 30 s application of domestic vinegar (4%–6% acetic acid) to prevent further discharge of unfired nematocysts remaining on the skin. Conversely, alcohol, methylated spirits and fresh water should be carefully avoided, since they could massively discharge nematocysts; pressure immobilization bandaging should also be avoided, as laboratory studies show that it stimulates additional venom discharge from nematocysts. Most treatment approaches are presently founded on relatively weak evidence; therefore, further research (especially randomized clinical trials) is strongly recommended. Dissemination of appropriate treatment modalities should be deployed to better inform and educate those at risk.
Adequate signage should be placed at beaches to notify tourists of the jellyfish risk.
Swimmers in risky areas should wear protective equipment.
Mar. Drugs 2013, 11 524 Keywords: jellyfish; cnidarians; cubozoans; stings; envenomation;pain; evidence-based treatment; vinegar; hot water; ice pack
Jellyfish belong to the phylum Cnidarians. The phylum is subdivided into five classes (see Figure 1:
Staurozoa (Stauromedusae); Scyphozoa (true jellyfish); Hydrozoa (Portuguese Man O’ War, fire corals and hydroids); Cubozoa (box jellyfish); and Anthozoa (sea anemones and true corals) ) and is composed of about 10,000 species, with 100 of them known to be dangerous to humans [2,3].
Jellyfish have a bell-shaped body (umbrella) of different sizes, with a varying number of tentacles, depending on the species. The tentacles reach from a few millimeters up to 40 m in length, depending on the species, with their color ranging from transparent to whitish, yellowish, purple or bluish [2,3].
The tentacles present specialized epidermic cells, called cnidocytes, that contain three categories of organelles, called cnidae (and also cnidocysts). Nematocysts, one of the three categories of cnidae, are hollowed capsules containing a tightly coiled and folder thread immersed in the cnidarians’ venom [1,2,4]. Nematocyst thread tubules evert so that the venom is injected on the outside of the thread tube. Some thread tubes are also hollowed and can discharge venom through the end [1–3].
Tentacles contain from a few thousand to several billion nematocysts [1,2].
Nematocysts are discharged onto the skin within a fraction of a second, making a jellyfish nematocyst discharge one of the most rapid mechanical events in nature . Nematocysts can function even when separated or if the organism is dead, although discharge rate decreases after death [1,6,7].
Discharge of the jellyfish venom is triggered by mechanical stimuli (such as skin rubbing or tentacle traction) , sudden increase in the osmotic pressure of the capsular fluid due to the removal of bound calcium ions  and sudden relaxation of spring-like tensions in the nematocyst collagen framework . The above stimuli activate the uncoiling of the thread, which penetrates into the tissues, causing the nematocyst to discharge venom [8,10].
Although all cnidarians are capable of envenomation, most are harmless to humans, as some do not have nematocyst shafts of sufficient length to enable the thread to deposit toxins deep enough into the epidermis [1,11] or might produce toxins that do not cause significant harm to humans . Harmful cnidarians include vertebrate feeders or bigger jellyfish able to release large amounts of toxin [1,2].
Jellyfish are present in all oceans of the world [2,3], with their stings being commonly observed in warm tropical marine waters [13,14], as well as in more northern regions, such as the United Kingdom , France  and Norway . The geographic distribution of jellyfish seems to be undergoing an impact by global warming [18–20].
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Figure 1. Cnidarians phylum: Main species by family and class.Mar. Drugs 2013, 11 526
It has been estimated there are 150 million jellyfish stings a year , with some Pacific areas reporting up to 800 daily events at one single beach [22,23]. Therefore, beyond being a public health issue, jellyfish also constitute a threat to tourism .
Skin contact with nematocysts resembles a prick, and the subsequent inflammation and nerve irritation produces pain, swelling and itching, potentially leading to skin necrosis in more severe stings (often from Australian chirodropid cubozoans) [2,25,26]. The local effect of the venom is due to the penetration of the thread and the activity of various compounds, like phospholipase A2 [7,27], as well as exocytosis of mast cell granules (and, thus, possibly histamine release) [28,29]. Nematocysts can also cause potential systemic symptoms—as a result of the toxins entering the general circulation —including gastrointestinal (mainly Physalia physalis and Pelagiidae spp.), muscular (Physalia and cubozoans spp.), cardiac (Physalia and cubozoans spp.), neurological (Physalia and cubozoans spp.) and allergic manifestations (Pelagiidae and cubozoans spp.). Jellyfish toxins reportedly also include hemolytic and lethal fractions [1,30,31]. The lethal fractions may contain cardiotoxins, able to produce ventricular arrhythmias and cardiac arrest, and neurotoxins [1,30,31], which may cause respiratory failure and respiratory arrest . Intravascular hemolytic fractions can also precipitate acute renal failure . Cnidarians’ venom is also immunogenic, capable of generating antibody response [1,4,24].
There has been a wealth of research done on the treatment of cnidarians’ stings, but confusion still exists as to what is the most effective first aid and clinical management [32–35]. Hence, there is an urgent need to consolidate a shared protocol for the management of these accidents.
Several authors have summarized the literature on the jellyfish phenomenon and the evidence concerning the various treatment approaches. Our aim was to integrate the knowledge reported by the most authoritative reviews and most recent research papers.
PubMed was searched for the following terms: “(jellyfish OR cnidarians OR medusae OR cubozoans OR Physalia OR Portuguese Man O’ War OR carybdeids or Pelagiidae OR cyanidae) AND (envenomation OR sting OR pain OR tentacles OR treatment OR management OR nematocyst OR discharge OR vinegar OR sea water OR alcohol OR ice OR cold water OR ammonia OR antidote OR methylated spirits)”, selecting only the reviews. Four of them were considered on the basis of the title, abstract, relevant and informative content, study area, profile of authors and journals. Using a function of PubMed, all the related citations were retrieved, discarding identical items and parts of publications by the same first author after examining the title and abstract. Further relevant articles were also retrieved from the referenced studies, employing Google Scholar in addition to PubMed. Reviews, commentaries, editorials, letters to editors, randomized and nonrandomized controlled trials, observational/case series studies with and without controls, laboratory studies, case reports and expert opinions were considered. Articles in English were largely preferred, and priority was given to works from the most reputable authors published in more established and referenced journals and books.
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3. Main Stinging Pelagic Cnidaria (Figure 1 Illustrates the Taxonomy of Cnidarians)
3.1. Physalia Species Physalia species are improperly believed to be “jellyfish”: They are a Siphonophore colony of animals in the class hydrozoa. Two major Physalia spp. are commonly classified within this
(1) Physalia physalis (the Portuguese Man O’ War): This worldwide species has a boat-like pneumatophore 2–25 cm long, with multi-tentacles measuring from 10 m up to 30 m ; yet, it is not a true jellyfish. This species is responsible for a large number of stings, with some being fatal.
(2) Physalia utriculus (the Blue Bottle): This Indo-Pacific, Indian Ocean and South Atlantic species is smaller than P. physalis, the float being up to 10 cm long and 5–6 cm wide, with a predominant fishing tentacle extending a maximum of 2–5 m [1,36].
The pneumatophore and the predominant tentacle are usually bright bluish, although in the Atlantic specimens, they may be purplish. This float allows them to sit on the surface of the ocean and lean horizontally when the wind blows, sailing with the wind, as well as being carried by water currents [2,3,26].
Physalia spp., which are responsible for a substantial proportion of cnidarians’ stings worldwide, have a widespread distribution . Both Physalia physalis and Physalia utriculus may be found in Indo-Pacific areas, the Indian Ocean and the South Atlantic , whereas in the North Atlantic and European coasts, only the Portuguese Man O’ War has been reported . Physalia spp. are more frequently found in hot and temperate waters [2,16,26]; however, these hydrozoans can occasionally be found cast ashore in cold Atlantic waters (e.g., North France, Belgium and the South West of England). In Australia, another multi-tentacled Physalia sp. has been reported .
As they float on the ocean surface, often in big swarms, Physalia spp. represent a potentially significant hazard to swimmers. Physalia stranded on beaches are still capable of stinging if handled, even after several days of dehydration .
Physalia stings are normally quite painful and severe, with the Portuguese Man O’ War potentially also causing major systemic symptoms . Physalia stings are normally multiple, always causing local symptoms with instantaneous pain: linear, crossed skin wheals longer than 20 cm with intradermal oedema in the areas having contact with the tentacles . Some severe skin injuries become necrotic within 24 h, evolving into scabs lasting for about two weeks before resolving and causing enduring (if not permanent) erythematous scars . The skin lesions of Physalia are quite easy to recognize, with typical spherical nematocysts detected by skin scrapings .
Physalia utriculus usually causes local pain only and, very rarely, minor systemic symptoms. By contrast, many patients with Physalia physalis stings suffer systemic symptoms, which generally are gastrointestinal (abdominal ache and nausea/vomiting) and/or muscular (spasms, pain). However, severe envenomations from Physalia may even produce neurological (headache, drowsiness, fainting, confusion) and cardio-respiratory syndromes (dyspnea, precordialgia). Systemic effects generally disappear rapidly with early first aid (hence, they are mostly described by the patients themselves) or Mar. Drugs 2013, 11 528 may last for hours . Serious envenomations have been reported from both sides of the Atlantic [39–41]. In 2011, about 10% of Physalia physalis victims in Aquitaine (France) presented life-threatening systemic conditions (especially respiratory distress), which required hospitalization .
Three fatal envenomations from Physalia have also been reported on the Southern Atlantic coasts of the United States [1,42].
Although first aid of Physalia stings is still quite controversial, the most effective treatment to alleviate pain is tentacle removal, followed by hot water application on the stung skin area. In a randomized controlled trial (RCT) conducted on 96 swimmers accidentally stung by Physalia, there was strong evidence (p 0.002) of decreased pain at 10 and 20 min post-treatment with hot water immersion at 45 °C, as compared to ice packs . These findings were somewhat confirmed by Bowra  in a cross-over study, which reported that victims treated with hot showers were more likely (p 0.001) to benefit from stronger and quicker pain relief, as compared with those treated with ice packs.
Despite being conducted with a loose design (no statistical analysis and no controls employed), one study suggested ice packs as an effective remedy to alleviate pain from Physalia stings .
According to Exton , one single skin application of ice packs resolved pain in 100% of 82 victims with mild pain; a second ice pack application resolved the symptoms in 98% of another 45 patients suffering from moderate pain and in 75% of 32 patients suffering from severe pain.
Though being advocated by a few authors  and endorsed by laboratory evidence  and a RCT , topical vinegar is not universally accepted as treatment [1,31], as it seemingly increases nematocyst discharge from some Physalia species [1,48]. In particular, nematocyst discharge from the multi-tentacled Physalia species living in Australian waters was observed under the microscope after exposing segments of tentacles to methylated spirits (grade 5 in a scale 1 to 5) and acetic acid (grade 2) in the laboratory [49,50]. Furthermore, a recent in vitro study  confirmed that pieces of Physalia physalis tentacles exposed to vinegar promptly caused thousands of nematocysts to discharge.