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Cnidaria Envenomation
Updated: Aug 18, 2008
Introduction
Background
Cnidaria (formerly Coelenterata) are in the phylum of aquatic invertebrates responsible for more envenomations than any other marine phylum. Close to 9000 species of Cnidaria are known, of which approximately 100 are toxic to humans. These animals have a gastrovascular cavity with a single opening used in digestion and circulation. Another characteristic feature is the presence of stinging cells or nematocysts. Human envenomations occur from all 4 classes in this phylum: (1) Hydrozoa (Portuguese man-of-war and fire coral), (2) Scyphozoa (true jellyfish), (3) Cubozoa (box jellyfish), and (4) Anthozoa (soft corals and sea anemones). Of the many toxic species, 3 species or conditions deserve attention because they are life-threatening or extremely common: the box jellyfish Chironex fleckeri, the carybdeid Carukia barnesi (Irukandji syndrome), and the bluebottle or Portuguese man-of-war.
Pathophysiology
The toxin of Cnidaria is located in cnidocytes, which are stinging cells composed of organelles called nematocysts. Nematocysts are present on the outer surfaces of tentacles or near the mouth. Nematocysts are contained within the cnidoblast or the outer capsule. On the external surface of the cnidoblast is the cnidocil (trigger point), which can be triggered by mechanical or chemical stimuli or may have remote and local control. At the base of the cnidocil is a hollow, coiled, sharp, threaded tube containing venom. The threaded tubes have denticles, which give the uncoiling thread cutting power like a drill. Extruded threads may reach up to 1 mm in length, a distance that is sufficient to penetrate the dermis of human skin. It is currently believed that the explosive release of the thread is caused by a sudden release of springlike tensions stored in the collagenous structural compartment. This is likely due to the sudden removal of bound calcium ions, resulting in a sudden increase in osmotic pressurein the capsular fluid.
The venom of many species is complex and largely unknown. The majority of toxins contain a complex mixture of polypeptides and proteins including (1) catecholamines, (2) histamine, (3) hyaluronidase, (4) fibrinolysins, (5) kinins, (6) phospholipases, and (7) various hemolytic, cardiotoxic, and dermatonecrotic toxins.
Hydrozoa class
The Hydrozoa class contains Physalia species (ie, Portuguese man-of-war or bluebottle) and hydroid corals. Portuguese man-of-war is not a true jellyfish but rather a siphonophore colony of hydrozoans with 4 different groups of animals. The result is a free-swimming organism with tentacles hanging from a gas-filled float, which acts as a sail, allowing wind-assisted travel. At least 2 Physalia species are of importance: (1) the larger Physalia physalis, which is found in the Atlantic Ocean from Nova Scotia to the Caribbean Sea; and (2) the smaller Physalia utriculus, which is found in the Pacific and Indian Oceans. Tentacles may reach up to 100 ft in length and contain up to a million nematocysts.
Detached tentacles on the beach are hazardous because they are capable of releasing venom for several weeks. Physalia species are one of the most commonly encountered marine envenomations in the United States and South Pacific. At least 3 confirmed deaths are attributed to P physalis.
Fire corals (Millepora) are typically encountered off the Florida coast and in the Caribbean and produce minimal toxicity, predominantly local pain.
Hydroid corals are sessile creatures that can attach to rocks, coral, seaweed, or pilings. A typical reaction is a mild stinging sensation with occasional development of burning pain and lymphadenopathy.
Scyphozoa class
The Scyphozoa class contains true jellyfish. In the United States, true jellyfish are the most common Cnidaria species to cause envenomation. Sea nettles Chrysaora species and Cyanea species are located along the Atlantic coast, with a high concentration near the Chesapeake Bay. Envenomations caused by organisms in the class Scyphozoa are less severe than those caused by Portuguese man-of-war.
Cubozoa class
The Cubozoa class contains the most toxic marine organisms, box jellyfish (Chironex fleckeri) and sea wasp (Chiropsalmus quadrigatus). The box jellyfish is the most dangerous jellyfish known with at least 67 deaths attributed to its envenoming. They are known to move into shallow waters in pursue of prey, thereby invading popular swimming areas. It is the only jellyfish with an antivenom. These animals are found in northern Australia and have not been reported in North American waters.
Carukia barnesi is also in this class and produces Irukandji syndrome. The mechanism of Irukandji syndrome is not known. Although only C barnesi is conclusively known to cause this condition, a number of other jellyfish are also likely responsible. The venom of C barnesi contains a sodium channel modulator that is linked to increased catecholamine release, which explains the early hyperadrenergic state demonstrated by these patients. The mechanism for cardiac dysfunction is yet to be elucidated as to whether it is the result of a myotoxin, due to excessive catecholamines, or both.
Anthozoa class
Anthozoa class contains sea anemones and corals. Most Anthozoa organisms are sessile creatures, and anemones found within the United States tidal zones have minimal toxicity. The sea anemone Phyllodiscus semoni (night or wasp-sea anemone) located in the Western Pacific Ocean is reported to cause fulminant dermatitis and acute renal failure in humans.
Corals
Corals are important components of living reefs. Risk of infection from a coral cut is of greater concern than the toxic effects of the coral.
Frequency
United States
Jellyfish envenomations occur in coastal areas of the United States, with highest frequency during summer. Envenomations by Physalia species are the most common jellyfish encounter prompting evaluation in the emergency department. Cases of seabather’s eruption occur in clusters along the East Coast and Caribbean.
International
An estimated 40,000-50,000 marine envenomations occur annually. Approximately 10,000 Cnidaria envenomations occur each summer off of the east coast of Australia, the vast majority of which are due to Physalia species. Each season, the Royal Darwin Hospital in Australia treats more than 40 patients with jellyfish encounters. A prospective evaluation of envenomings from that hospital over a 12-month period from 1999-2000 revealed that 70% resulted from the box jellyfish.1 The remaining 30% mostly involved other Cubozoa species. This study may suggest that box jellyfish envenomings are common but also suggests the severity of the encounters. Many beaches in Australia have large amounts of vinegar placed in prominent positions along swimming beaches in jellyfish-endemic areas. This likely reduces the amount of emergency department visits for mild-to-moderate encounters.
Mortality/Morbidity
Fatal envenomations due to box jellyfish occur in tropical waters of northern Australia. Fatalities have occurred rapidly, within 60 seconds, from this species. At least 67 deaths have been attributed to the box jellyfish.
At least 3 deaths have occurred due to Physalia species since 1989 in the United States.
In addition, a 4-year-old boy died within 40 minutes from an apparent envenoming by the jellyfish Chiropsalmus quadrigatus in the Gulf of Mexico.2
Most patients who develop Irukandji syndrome recover within 1-2 days, but 2 deaths were reported in Queensland, Australia, in 2002.
Patients have reported delayed hypersensitivity reactions as well as hypopigmented and hyperpigmented areas in the regions of the original tentacles.
Race
No scientific data substantiate any differences in Cnidaria envenomation that are attributable to race.
Sex
No scientific data substantiate any differences in Cnidaria envenomation that are attributable to gender.
Age
Although not well studied, a large number of pediatric cases are reported in the literature, likely due to the shallow water swimming. The smaller body mass and thinner skin may make infants and children more susceptible to jellyfish envenomations.
Clinical
History
- Envenomations usually result in 3 main types of mechanisms: immediate allergic, immediate toxic, and delayed allergic response.
- Obtain the following information regarding the envenomation:
- Time of envenomation
- Nature of incident - Geographic location, quality of symptoms, progression of symptoms
- Description of animal
- Toxicity depends on the following:
- Age of patient
- Underlying health of patient (especially those with hepatic disease)
- Potency of venom
- Number of nematocysts triggered
- Amount of skin involved
- Look for envenomation lesions in patients with unexplained near drowning or collapse in water.
Physical
- Chironex fleckeri is the most toxic jellyfish in the world. However, most encounters appear to result in mild envenoming. Stings from small C fleckeri are incapable of penetrating adult skin but may cause papular-urticarial eruptions in infants and small children. Stings from larger animals can be severe.
- Patients initially develop severe pain despite removal of the tentacle. Tentacle marks are purple to brown and may resemble that made by a whip. Areas rapidly develop erythema, edema, and vesicles and may go on to full-thickness necrosis over the next 1-2 weeks. Death is probable if the total length of the wheals is greater than 6-7 meters.
- Initial systemic reactions include headache, malaise, fever, nausea, vomiting, muscle spasm, pallor, respiratory distress, hemolysis, and acute renal failure.
- Death may be rapid (minutes) and is often the result of combined cardiovascular and respiratory arrest. In northern Australia, 67 deaths have been reported as a result of C fleckeri envenomings. Deaths can also occur by drowning secondary to incapacitation following painful envenomations.
- Irukandji syndrome is most likely due to encounters with Carukia barnesi, although other jellyfish may also be responsible. It derives its names from the Aboriginal tribe that formerly inhabited the areas in and around Cairns.
- The initial sting from C barnesi is often mild to moderately painful but well tolerated. Approximately 30 minutes after envenomation (range, 5 min to 2 h) patients develop severe low back pain, cramping abdominal pain, nausea, vomiting, profuse sweating, headache, restlessness, agitation, tachycardia, and hypertension.
- Severe toxicity may involve pulmonary edema and cardiac failure. Although the systemic reaction can be significant, the envenomation site frequently is not visible.
- In regards to most jellyfish encounters, the most common presentation is a painful papular-urticarial eruption at the site of contact. Lesions can last for minutes to hours, and the rash may progress to urticaria. Further progression can lead to vesicular, hemorrhage, or necrotizing lesions. "Sea lice" or seabather's eruption affects covered areas of the body and is a result of trapped larvae of certain thimble jellyfish. The severely pruritic urticarial lesions can last up to 2 weeks.
- Uncommon local reactions include angioedema, recurrent reactions, contact dermatitis, and papular urticaria.
- Systemic reactions can develop along with local cutaneous findings including weakness, headache, nausea, vomiting, muscle spasm, fever, pallor, syncope, respiratory distress, and paresthesias.
- Ocular contact has resulted in conjunctivitis, chemosis, corneal ulcerations, and lid edema.
- Immediate and delayed hypersensitivity reactions may occur, but anaphylaxis is rare.
- Chronic reactions include keloids, granulomas, hyperpigmentations, fatty atrophy, contractions, and vascular spasms.
- Ingestion of jellyfish has resulted in abdominal pain, cramping, and generalized urticaria.
Causes
Contact with a Cnidaria is the cause of envenomation, although some patients have developed mild symptoms after ingestion of jellyfish.
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Further Reading
Keywords
jellyfish envenomation, cnidaria envenomation, jellyfish sting, box jellyfish, aquatic invertebrates, Hydrozoa, Portuguese man-of-war, fire coral, Scyphozoa, true jellyfish, Cubozoa, Anthozoa, sea anemone, coelenterate envenomation,
