Aquatic Antagonists: Jellyfish Stings

Jellyfish stings are one of the most common marine injuries, with an estimated 150 million stings occurring annually worldwide.¹ Most jellyfish stings result in painful localized skin reactions that are self-limited and can be treated with conservative measures including hot water immersion and topical anesthetics. Life-threatening systemic reactions (eg, anaphylaxis, Irukandji syndrome) can occur with some species.^2-4 Mainstream media reports do not reflect the true incidence and variability of jellyfish-related injuries that are commonly encountered in the clinic.³

Characteristics of Jellyfish

There are roughly 10,000 known species of jellyfish, with approximately 100 of them posing danger to humans.⁵ Jellyfish belong to the phylum Cnidaria, which is comprised of 5 classes of both free-floating and sessile animals: Staurozoa (stauromedusae), Hydrozoa (hydroids, fire corals, and Portuguese man-of-war), Scyphozoa (true jellyfish), Anthozoa (corals and sea anemones), and Cubozoa (box jellyfish and Irukandji jellyfish).^1,2,6 Jellyfish typically have several tentacles suspended from a free-floating gelatinous body or bell; these tentacles are covered with thousands of cells unique to Cnidaria called nematocytes or cnidocytes containing specialized stinging organelles known as nematocysts. When triggered by physical (eg, human or foreign-body contact) or chemical stimuli, each nematocyst ejects a hollow filament or barb externally, releasing venom into the victim.^7,8

FIGURE 1. Pacific sea nettles (Chrysaora fuscescens) of class Scyphozoa in medusa form.

The scyphozoan, hydrozoan, and cubozoan life cycles generally consist of a bottom-dwelling, sessile polyp form that produces multiple free-swimming ephyrae through an asexual reproductive process called strobilation. These ephyrae grow into the fully mature medusae, recognizable as jellyfish (Figure 1).⁵ Additionally, jellyfish populations experience cycles of temporal and spatial population abundance and crashes known as jellyfish blooms. In 2017, Kaffenberger et al⁹ reviewed the shifting landscape of skin diseases in North America attributable to major changes in climate and weather patterns, including the rise in jellyfish blooms and envenomation outbreaks worldwide (eg, Physalia physalis [Portuguese man-of-war][Figure 2] along the southeastern US coastline, Porpita pacifica off Japanese beaches). Some research suggests jellyfish surges relate to climate change and human interactions with jellyfish habitats by way of eutrophication and fishing (removing predators of jellyfish).^9,10

FIGURE 2. Portuguese man-of-war (Physalia physalis). Jellyfish often wash ashore and cause injury to unsuspecting beach travelers; footprint in upper right for size comparison.

Clinical Presentation

Jellyfish injuries can vary greatly in clinical symptoms, but they do follow some basic patterns. The severity of pain and symptoms is related to the jellyfish species, the number of stinging cells (nematocysts) that are triggered, and the potency of the venom that is absorbed by the victim.^11-13 Most stings are minor, and patients experience immediate localized pain with serpiginous raised erythematous or urticarial lesions following the distribution of tentacle contact; these lesions have been described as tentaclelike and resembling a string of beads (Figure 3).¹² Pain usually lasts a couple hours, while the skin lesions can last hours to days and can even recur years later. This pattern fits that of the well-known hydrozoans P physalis and Physalia utriculus (bluebottle), which are endemic to the Atlantic and Indo-Pacific Oceans, respectively. The scyphozoan jellyfish causing similar presentations include Pelagia noctiluca (Mauve stinger), Aurelia aurita (Moon jellyfish), and Cyanea species. The cubozoan Chironex fleckeri (Australian box jellyfish or sea wasp) also causes tentaclelike stings but is widely considered the most dangerous jellyfish, as its venom is known to cause cardiac or respiratory arrest.^4,11 More than 100 fatalities have been reported following severe envenomations from C fleckeri in Australian and Indo-Pacific waters.⁶

FIGURE 3. Serpiginous tentaclelike lesions following a jellyfish-sting.

Stings from another box jellyfish species, Carukia barnesi, cause a unique presentation known as Irukandji syndrome. Carukia barnesi is a small box jellyfish with a bell measuring roughly 2 cm in diameter. It has nematocysts on both its bell and tentacles. It inhabits deeper waters and typically stings divers but also can wash ashore and injure beach tourists. Although Irukandji syndrome usually is associated with C barnesi, which is endemic to Northern Australian beaches, other jellyfish species including P physalis rarely have been linked to this potentially fatal syndrome.^6,11 Unlike the immediate cutaneous and systemic findings described in C fleckeri encounters, symptoms of Irukandji-like stings can be delayed by up to 30 minutes. Patients may present with severe generalized pain (lower back, chest, headache), signs of excess catecholamine release (tachycardia, hypertension, anxiety, diaphoresis, agitation), or cardiopulmonary decompensation (arrhythmia, cardiac arrest, pulmonary edema).^6,11,14.15 Anaphylactic reactions also have been reported in those sensitized by prior stings.¹⁶

Management

Prevention of drowning is key in all marine injuries. Rescuers should remove the individual from the water, establish the ABCs—airway, breathing, and circulation—and seek acute medical attention. If immediate resuscitation is not required, douse the wound as soon as possible with a solution that halts further nematocyst discharge, which may contain alcohol, vinegar, or bicarbonate, depending on the prevalent species. General guidance is available to providers through evidence-based, point-of-care databases including UpToDate and DynaMed, as well as through the American Heart Association (AHA) or a country’s equivalent council on emergency care if residing outside the United States. Pressure immobilization bandages as a means of decreasing venom redistribution is no longer recommended by the AHA because animal studies have shown increased nematocyst discharge after pressure application.¹⁷ As such, touching or applying pressure to the affected area is not recommended until after a proper rinse solution has been applied. Tentacles may be removed mechanically with gloved hands or sand and seawater with minimal compression or agitation.

When acetic acid is appropriate, such as for cubozoan stings, commercially available vinegar (5% acetic acid in the United States) is preferred.^16,17 Tap water can cause discharge of nematocysts, and seawater is preferred when no other solution is available.¹⁸ Most marine venoms are heat labile. Immersion in hot water can produce pain relief, but ice can be just as efficacious and is preferred by some patients. Prior reports of patients stung by Physalia species demonstrated greater pain relief with hot water immersion compared to ice pack application.^18,19