(For fish poisonings [eg, scombroid, ciguatera, fugu] and paralytic shellfish poisoning, see Fish and Shellfish Poisoning.)
Some marine bites and stings are toxic; all create wounds at risk of infection with marine organisms, most notably Vibrio sp, Aeromonas sp, and Mycobacterium marinum.
Shark bites result in jagged lacerations with near-total or total amputations and should be treated in the same way as other major trauma (see Evaluation and Treatment).
Cnidaria (Coelenterates, such as jellyfish and sea anemones)
Cnidaria include the following:
Cnidaria are responsible for more envenomations than any other marine animal. However, of the 9000 species, only about 100 are toxic to humans. The multiple, highly developed stinging units (nematocysts) on cnidaria tentacles can penetrate human skin; one tentacle may fire thousands of nematocysts into the skin on contact.
Symptoms and Signs
Lesions vary with the type of cnidaria. Usually, lesions initially appear as small, linear, papular eruptions that develop rapidly in one or several discontinuous lines, at times surrounded by a raised erythematous zone. Pain is immediate and may be severe; itching is common. The papules may vesiculate and proceed to pustulation, hemorrhage, and desquamation. Systemic manifestations include weakness, nausea, headache, muscle pain and spasms, lacrimation and nasal discharge, increased perspiration, changes in pulse rate, and pleuritic chest pain. Uncommonly, fatal injuries have been inflicted by the Portuguese man-of-war in North American waters and by members of the Cubomedusae order, particularly the box jellyfish (sea wasp, Chironex fleckeri), in Indo-Pacific waters.
Cnidaria sting treatment includes removal of adherent tentacles with a forceps (preferably) or fingers (double-gloved if possible) and liberal rinsing to remove invisible stinging cells. The type of rinse varies by the stinging organism:
Any difficulty breathing or alteration in level of consciousness, no matter how mild, is a medical emergency, requiring transport to a medical center and possibly injection of epinephrine.
Symptoms are treated supportively. Pain caused by sea nettle stings, usually short-lived, can be relieved with baking soda in a 50:50 slurry applied to the skin. For other stings, hot water or cold packs, whichever feels better, can help relieve pain, as can an NSAID or other analgesic. For severe pain, opioids are preferred. Painful muscle spasms may be treated with benzodiazepines. IV fluids and epinephrine can be given if shock develops. Antivenom is available for the stings of the box jellyfish C. fleckeri but not for the stings of North American species.
This stinging, pruritic, maculopapular rash affects swimmers in some Atlantic locales (eg, Florida, Caribbean, Long Island). It is caused by hypersensitivity to stings from the larvae of the sea anemone (eg, Edwardsiella lineate) or the thimble jellyfish (Linuche unguiculata). The rash appears where the bathing suit contacts the skin. People exposed to these larvae should shower after taking off their bathing suit. Cutaneous manifestations can be treated with hydrocortisone lotion and, if needed, an oral antihistamine. More severe reactions may require the addition of oral or IV prednisone.
Stingrays once caused about 750 stings/yr along North American coasts; the present incidence is unknown, and most cases are not reported. Venom is contained in the one or more spines on the dorsum of the animal's tail. Injuries usually occur when an unwary swimmer wading in ocean surf, bay, or backwater steps on a stingray buried in the sand and provokes it to thrust its tail upward and forward, driving the dorsal spine (or spines) into the patient's foot or leg. The integumentary sheath surrounding the spine ruptures, and the venom escapes into the patient's tissues.
Symptoms and Signs
The main symptom is immediate severe pain. Although often limited to the injured area, the pain may spread rapidly, reaching its greatest intensity in < 90 min; in most cases, pain gradually diminishes over 6 to 48 h but occasionally lasts days or weeks. Syncope, weakness, nausea, and anxiety are common and may be due, in part, to peripheral vasodilation. Lymphangitis, vomiting, diarrhea, sweating, generalized cramps, inguinal or axillary pain, respiratory distress, and death have been reported.
The wound is usually jagged, bleeds freely, and is often contaminated with parts of the integumentary sheath. The edges of the wound are often discolored, and some localized tissue destruction may occur. Generally, some swelling is present. Open wounds are subject to infection.
Injuries to an extremity should be gently irrigated with salt water in an attempt to remove fragments of spine, glandular tissue, and integument. The spine should be removed in the field only if it is superficially embedded and is not penetrating the neck, thorax, or abdomen or creating a through-and-through injury of a limb. Significant bleeding should be staunched with local pressure. Warm water immersion, although recommended by some experts, has not been verified as an effective early treatment for stingray injuries.
In the emergency department, the wound should be reexamined for remnants of the sheath and debrided; a local anesthetic may be given as needed. Embedded spines are treated similarly to other foreign bodies. Patients stung on the trunk should be evaluated closely for puncture of viscera. Treatment of systemic manifestations is supportive. Tetanus prophylaxis should be given, and an injured extremity should be elevated for several days. Use of antibiotics and surgical wound closure may be necessary.
Mollusks include cones (including cone snails), cephalopods (including octopi and squids), and bivalves.
This type is the only known dangerous cone in North American waters. Its sting causes localized pain, swelling, redness, and numbness that rarely progresses to paralysis or shock.
Treatment is largely supportive. Local measures seem to be of little value, and reports that local injection of epinephrine and neostigmine are helpful are unproved. Severe Conus stings may require mechanical ventilation and measures to reverse shock.
These snails are a rare cause of marine envenomation among divers and shell collectors in the Indian and Pacific Oceans. When the snail is aggressively handled (eg, during shell cleaning, when placed in a pocket), it injects its venom through a harpoon-like tooth. Multiple neurotoxins in the venom block ion channels and neurotransmitter receptors, resulting in paralysis, which is usually reversible but has resulted in some deaths.
Treatment is supportive and may include local pressure immobilization (eg, by wrapping wide crepe or other fabric bandages around the limb), immersion in hot water, and tetanus prophylaxis. Severe cases may require respiratory support.
The bites of North American octopi are rarely serious.
Bites from the blue-ringed octopus, most common in Australian waters, cause tetrodotoxin envenomation, with local anesthesia, neuromuscular paralysis, and respiratory failure; treatment is supportive.
The large (up to 1.5 m), aggressive Humboldt squid is present off the west coast of the Americas; it has reportedly bitten fishermen and divers. Other squid species are of less concern.
Sea urchins are present worldwide. Most sea urchin injuries result when spines break off in the skin and cause local tissue reactions. Without treatment, the spines may migrate into deeper tissues, causing a granulomatous nodular lesion, or they may wedge against bone or nerve. Joint and muscle pain and dermatitis may also occur. A few sea urchins (eg, Globiferous pedicellariae) have calcareous jaws with venom organs, enabling them to inject venom, but injuries are rare.
Diagnosis is usually obvious by history. A bluish discoloration at the entry site may help locate the spine. X-rays can help when the location is not obvious during examination.
Treatment is immediate removal. Vinegar dissolves most superficial spines; soaking the wound in vinegar several times a day or applying a wet vinegar compress may be sufficient. Hot soaks may help relieve pain. Rarely, a small incision must be made to extract the spine; care must be taken because the spine is very fragile. A spine that has migrated into deeper tissues may require surgical removal. Once spines are removed, pain may continue for days; pain beyond 5 to 7 days should trigger suspicion of infection or a retained foreign body.
G. pedicellariae stings are treated by washing the area and applying a mentholated balm.
Last full review/revision February 2013 by Robert A. Barish, MD, MBA; Thomas Arnold, MD
Content last modified May 2013