Cnidaria Envenomation Clinical Presentation

Updated: Apr 27, 2017
  • Author: Spencer Greene, MD, MS, FACEP, FACMT; Chief Editor: Joe Alcock, MD, MS  more...
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Three different mechanisms are responsible for toxicity from Cnidaria envenomations: immediate toxicity, immediate allergic reaction, and delayed allergic response.

When evaluating a patient with a suspected envenomation, it is essential to obtain the following information: (1) time of envenomation; (2) location of the incident; (3) description of the animal; (4) onset, progression, and quality of signs and symptoms; and (5) what treatments have thus far been attempted.

The severity of the envenomation is determined by a variety of factors, including (1) size, age, species, and overall health of the animal; (2) the size, age, and underlying health of the patient; (3) the surface area of the involved skin; and (4) the duration of contact.

Though not applicable to known envenomations, it is always wise to consider envenomation in the differential diagnosis of unexplained drowning and near-drowning.


Physical Examination

Pain and dermatologic abnormalities are the most obvious, and often the only, signs and symptoms of a Cnidarian envenomation. Erythema develops rapidly after envenomation, followed by edema and purple-brown vesicular lesions, often found in a whiplike pattern. Most lesions last for minutes to hours, but some may hemorrhage or progress to full-thickness necrosis over the next 1-2 weeks.

Sea bather's eruption, or "sea lice", is characterized by small, intensely pruritic urticarial lesions confined to covered areas of the body. It develops when the larvae of several species of thimble jellyfish become trapped and maintain prolonged contact with the victim's skin. The lesions may last for up to 2 weeks but have no permanent consequences

Ocular abnormalities such as conjunctivitis, chemosis, corneal ulcerations, and lid edema have been observed following envenomations.

Findings indicative of systemic envenoming include pulmonary edema, variable blood pressure, tachycardia, weakness, headache, nausea, vomiting, muscle spasm, fever, pallor, syncope, respiratory distress, paresthesias, acute renal failure, hemolysis, myocardial infarction, and cardiopulmonary arrest. [11, 12] These are most likely to occur following envenomation from C fleckeri or P physalis. Oftentimes, the local findings are minimal.

Uncommon complications following Cnidaria envenomation include Guillain-Barré syndrome, [13] mononeuropathy, [14] and Takotsubo cardiomyopathy. [15]

The constellation of low back pain, abdominal cramping, nausea, vomiting, diaphoresis, headache, and tachycardia is suggestive of Irukandji syndrome. [16, 17] This entity, named for the Aboriginal tribe that formerly inhabited the areas in and around Cairns, Australia, was first described in 1952 by Dr. Hugo Flecker. In 1964, Dr. Jack Barnes identified C barnesi as the Cnidarian responsible for the condition, and since then other cubozoans have been implicated in the syndrome. Typically, 30 minutes after envenomation (range, 5 min to 2 h) patients develop the aforementioned signs and symptoms. Major envenomations also feature restlessness, agitation, and progress to pulmonary edema and cardiac failure. [18] Despite the severity of the systemic reaction, the findings at the envenomation site are barely detectable.



Contact with a Cnidarian is the cause of envenomation, although some patients have developed mild symptoms after ingestion of jellyfish.



Immediate- and short-term complications from Cnidaria envenomations include (1) wound infection, (2) rhabdomyolysis, (3) acute renal failure, (4) hemolysis, (5) pulmonary edema, (6) respiratory paralysis, (7) cardiovascular collapse, and (8) death.

Long-term sequelae of jellyfish stings include keloid formation, granulomas, hyperpigmentation, fatty atrophy, contractions, and vascular spasms. Sclerosing dacrocystadenitis, possibly due to an immune response to an antigen challenge, developed in a 3-year old child several weeks after an envenomation to the lower extremities. [19]