Chapter 135: Marine Envenomations

• For most marine stings, local wound care, irrigation, tetanus immunization, wound exploration for foreign bodies, and selected antibiotic coverage are standard therapies.

• Hot water soaks are recommended for stingray, scorpion fish, echinoderm, and catfish stings.

• Dermatologic irrigation with vinegar, rubbing alcohol, household ammonia, baking soda, or papain will neutralize many coelenterate envenomations, including jellyfish.

• Antivenoms are available for stonefish, box jellyfish, and sea snake envenomations.

As more humans venture into aquatic environments for recreational activities, vacations, exotic destinations, and an improved quality of life, the opportunity for children to encounter venomous marine life that hide in reefs and shallow marine waters increases.^1,2 Also, as more aquarists collect exotic marine life for display in the home, the incidence of bites and stings will rise regardless of the geographic locale.^1,3 Hazardous marine life can be classified into four major groups:

• Venomous bites and stings, such as those inflicted by scorpion fish and the Portuguese man-o'-war.

• Shock injuries, such as from electric eels.

• Traumatogenic bites, such as from sharks and barracudas.

• Toxic ingestions or fish poisoning.⁴

This chapter will discuss venomous bites and stings.

Toddlers are most likely to be envenomed in shallow waters and are typically unable to give a detailed or reliable history. Young children may either step on poisonous marine animals or handle them resulting in extremity stings. Adolescents are more adventurous and frequent deeper waters as surfers,⁵ ocean swimmers, snorkelers, and scuba divers.⁶ This age group is also more susceptible to intoxication with ethanol or recreational drugs.¹

Coelenterates (phylum Cnidaria) include jellyfish, sea anemones, and corals. Jellyfish stings are the most common marine envenomations, with an estimated 500,000 annual stings occurring in the Chesapeake Bay and 250,000 in Florida. A commonly encountered jellyfish is the sea nettle (Chrysaora quinquecirrha), which is widely distributed in temperate and tropical waters. Even in colder marine regions such as Scandinavia, jellyfish envenomations are encountered. ⁷ One of the more feared jellyfishes is the Portuguese man-o'-war (Physalia physalis). This jellyfish is most commonly found in the Gulf of Mexico and off the Florida coasts between July and September. Its tentacles can reach up to 30 m in length (Fig. 135-1). The deadliest and most venomous of coelenterates is the box jellyfish or sea wasp of Australia (Fig. 135-2).^8–11

Pathophysiology

Coelenterates envenomate with organelles called nematocysts, which contain venom-bearing threads that reside within specialized epithelial cells on the tentacles. Each nematocyst is a capsule with a folded eversible tubule, carrying a variety of toxins with neurologic, cytolytic, and enzymatic effects. Upon contact or when encountering a change in osmolality, these threads are everted from the nematocysts to be thrust into the prey (Fig. 135-3). When a human is stung, the penetration reaches into the innervated and vascular dermis. Both living and dead coelenterates can envenomate, as can fragmented tentacles and “unfired” nematocysts on the skin. Venoms vary but generally contain histamine and kinin-like factors capable of causing systemic as well as local tissue effects. The venom in nematocysts is potentially dermatonecrotic, myotoxic, cardiotoxic, neurotoxic, and hemolytic.

Clinical Presentation

Mild coelenterate envenomation from true jellyfish or sea nettles generally causes local pruritus and characteristic linear, spiral, and painful urticarial lesions. The lesions often blister, and there is localized surrounding edema. The pain and stinging sensation occurs instantly, peaks within 60 minutes, and may persist for hours. Systemic symptoms from Portuguese man-o'-war stings may include nausea, vomiting, dysphagia, muscle cramps, myalgias, arthralgias, diaphoresis, and weakness.¹² In addition, hemolysis and renal failure have been described followingman-o'-war stings in pediatric patients.¹³ Severe dyspnea and oral swelling as a result of a facial jellyfish envenomation in an adolescent patient have also been reported.¹⁴ Secondary orbital inflammation has been documented in children suffering stings to the lower extremities.¹⁵ Other severe systemic symptoms include hemolysis, dysrhythmias, cardiovascular collapse, respiratory distress, paralysis, seizures, coma, and death.^16,17 The vast majority of Chironex fleckeri stings are not life threatening with painful skin welts as the major finding. However, fatalities that do occur usually do so within 5–20 minutes of the envenomation.¹⁸ According to one recent source, fatalities among Southeast Asian tourists are underestimated.¹⁹ Death in a child has been described in the literature following envenomation by the cuboid jellyfish (Chiropsalmus quadrumanus), which is found in the Atlantic and Indian Oceans.²⁰

Management

Treatment includes reassurance of the victim and immobilization of the injured part. Ice may provide some analgesia. The area is rinsed with sterile saline or seawater to maintain a condition isosmolar to seawater and to wash off unfired nematocysts. Fresh water is not recommended because it is hypoosmolar and often activates unfired nematocysts. As soon as possible apply a topical decontaminant. To inactivate nematocysts remaining on the skin, most sources recommend altering the pH by soaking the wounds with a weak acidic household vinegar (5% acetic acid solution).²¹ However, a recent study suggests that vinegar actually causes pain exacerbation or nematocyst discharge in the majority of species in North America and Hawaii.²² Hot water and topical lidocaine appear more widely beneficial in improving pain symptoms and are preferentially recommended. Unfortunately, these interventions may be difficult to obtain at the site of envenomation, such as the beach or diving sites. In these instances, removing the nematocysts and washing the area with saltwater may be considered.²² Inactivated nematocysts can also be removed by gentle shaving or scraping. In the absence of a razor and shaving foam, one can also use the edge of a credit card or an object with a similar edge such as a popsicle stick or clamshell.⁸

If the victim shows signs and symptoms of anaphylaxis, treat appropriately. In most cases, analgesics and antihistamines are helpful. As a substitute for vinegar, one can apply household ammonia, rubbing alcohol, baking soda paste, or a slurry containing papain, which is commonly found in meat tenderizers.¹⁴ Rubbing sand or pouring ethanol over the wounds has no proven efficacy. Human urine has actually been described as causing massive nematocyst discharge in Chironex tentacles and, contrary to popular belief, has little scientific basis for use.²³ Tetanus immunization is indicated, but prophylactic antibiotics are not.

Sea anemones (Fig. 135-4) and corals are sessile creatures that cause local urticarial reactions upon contact. Contact with hard (true) corals may cause lacerations that are treated with vigorous local wound care, topical antiseptics, and tetanus prophylaxis.

If a child is envenomated by an Australian box jellyfish, antivenom against Chironex is available in Australia and from major US city aquaria and certain theme parks, such as Sea World. The antivenom is ovine in derivation and has been administered safely in more than 75 episodes of envenomation. One ampule (20,000 units) can be administered IVPB, diluted in 1:5 ratio with crystalloid fluid, or it can be administered IM according to the manufacturer's instructions.²⁴ For the rapid onset of cardiotoxicity with severe envenomations, the antivenom should be given without delay and in proper doses to be lifesaving.¹⁸

To prevent coelenterate stings, ocean bathers should wear proper skin protection, such as a neoprene “wet suit” or Lycra “dive skin.” A commercially available jellyfish safe sun block is a topical sunscreen–jellyfish sting inhibitor combination that can be used to protect skin against stings and is recommended for anyone who will expose otherwise unprotected skin to jellyfish, fire corals, anemones, or other similar stinging creatures.²

Disposition

Mild stings responsive to hot water irrigation or vinegar therapy can be managed at home after a 3–4-hour observation. Children with systemic toxicity or inadequate pain control despite local wound treatment should be admitted for observation. Any child envenomed by a box jellyfish should be observed for 8 hours. Symptomatic patients may require antivenom.

There are more than 250 species of venomous fish, consisting mostly of shallow water reef or inshore fish. Stingrays are the most commonly encountered venomous fish, with more than 2000 stings reported annually. Eleven species of stingrays are found in US coastal waters.

On the West Coast, the round stingray (Urolophus halleri) is most commonly found; on the east coast and Caribbean, the southern stingray (Dasyatis americana) is most frequently encountered. They are flat, round-bodied fishes that burrow underneath the sand in shallow waters (Fig. 135-5 A and B). When startled or stepped on, the stingray thrusts its spiny tail upward and forward, driving its venom-laden stinging apparatus into the foot or lower extremity of the victim.

Varieties of scorpion fish include zebrafish and lionfish (Pterois), scorpion fish (Scorpaena), and stonefish (Synanceja), in increasing order of venom toxicity. Although more common in tropical waters of the Indo-Pacific, these fish are found in the shallow water reefs of the Florida Keys, Gulf of Mexico, southern California, and Hawaii. Lionfish are increasingly popular as aquarium pets (Fig. 135-6).^25,26

Catfish are found in both fresh and salt water. Stings occur from spines contained within an integumentary sheath on their dorsal or pectoral fins. The hands and forearms of fishermen and seafood handlers are the most common sting sites.

Pathophysiology

Stingrays have one to four venomous spines or barbs on the dorsum of a whip-like tail. The spines are retroserrated, so they anchor and may become difficult to remove (Fig. 135-7). As the sting is withdrawn, the sheath surrounding it ruptures and the venom is released. Parts of the sheath may be torn away and remain in the wound. The venom is intensely active, partially heat-labile, and causes varying degrees of local tissue necrosis and cardiovascular disturbances. One death of a 12-year-old male is described in the literature from a stingray spine that directly penetrated the child's chest wall, heart, and lung, resulting in myocardial necrosis and tamponade.²⁷

Scorpion fish have venomous spines on the dorsal, anal, and pelvic fins. This venom is also partially heat-labile. Stonefish have 13 dorsal spines harboring one of the most toxic fish venoms (Fig. 135-8).²⁸ Analysis of stonefish venom reveals several toxic components including hyaluronidase, substances with hemolytic activity, and biogenic amines, such as norepinephrine. Cardiotoxicity is primarily from verrucotoxin, a negative chronotropic and ionotropic agent that acts by inhibiting calcium channels.²

For catfish spine stings, heat-labile venoms comprise dermatonecrotic, vasoconstrictive, and other bioactive agents produce symptoms similar to those of mild stingray envenomations. A unique parasitic catfish, the Amazonian Candiru (genus Urinophilus), may invade its victim by swimming “upstream” into the human urethra. Acute painful hemorrhage may result if forceful extraction of the catfish is attempted.²⁹

Clinical Presentation

With stingrays, intense pain out of proportion to the apparent injury is the initial finding, peaking within 1 hour and lasting up to 48 hours. Signs and symptoms are usually limited to the injured area, but weakness, nausea, anxiety, and syncope have been reported.

Envenomations from lionfish, scorpion fish, and stonefish cause immediate intense pain that peaks within 60–90 minutes and persists for up to 12 hours. Local erythema or blanching, edema, and paresthesias may persist for weeks. Systemic findings include nausea and vomiting, weakness, dizziness, and respiratory distress. Although similar to those of the other scorpion fish, stonefish stings are more severe. Stonefish venom, a potent neurotoxin, can cause dyspnea, hypotension, and cardiovascular collapse within 1 hour and death within 6 hours. Local necrosis and severe pain may persist for days.

With catfish stings, burning and throbbing sensation occurs immediately but usually resolves within 60–90 minutes. The discomfort may last up to 48 hours. Systemic symptoms are rarely reported.

Management

Treatment of stingray wounds includes irrigation with sterile saline to dilute the venom and remove sheath fragments. The spine of the stingray including the venom gland is typically difficult to remove from the victim and radiographs may be necessary to locate the spine or retained fragments.³⁰ However, a recent large retrospective study of 119 stingray injuries found no positive radiographic evidence of foreign bodies in any of their patients.³¹

The injured part should be immersed in hot water, no warmer than 113ºF, for 30–90 minutes, to inactivate any heat-labile venom components.²³ Analgesics are usually required. Because of the penetrating nature of the envenomation, wounds should be debrided and left open. Tetanus immunization is updated if needed. Treatment with a broad-spectrum prophylactic antibiotic such as trimethoprim–sulfamethoxazole (TMP–SMX), ciprofloxacin, or a third-generation cephalosporin is recommended because of concern for infection by Vibrio species, as well as Staphylococcus and Streptococcus spp.³²

Treatment for scorpion fish and lionfish envenomation is immersion of the affected limb in hot water (113ºF) for 30–90 minutes, or until pain is relieved. Some case reports have documented failure to respond to standard warm water immersion therapy at 45ºC.²⁶ Wounds should be irrigated with sterile saline, explored, and cleaned of debris. The wound is left open and treatment with prophylactic antibiotics is initiated.³³ Local treatment for a stonefish sting is the same as that for envenomations by other scorpion fish, with special attention given to maintaining cardiovascular support.⁶ One recent report describes a case of foot stonefish envenomation treated by vacuum-assisted closure therapy as an easy to use, accessible, and simple adjuvant tool for management of large soft tissue necrosis.³³

There is a specific stonefish antivenom available in Australia.^2,35 The antivenom is an equine-derived product and carries the risk for inducing anaphylaxis. One 2 mL ampule of stonefish antivenom is diluted in 50 mL normal saline and given IVPB. A case series of eight patients suggests that the majority of stonefish envenomations do not result in significant morbidity or mortality and usually require only supportive management.³⁶ Another larger more recent series of 57 patients suffering stonefish envenomation noted severe pain in 95% of victims with half of the patients requiring hospital admission. All responded to analgesic medications and antibiotic coverage and there was no mention of antivenom administration.³⁷ It remains uncertain whether stonefish antivenom is efficacious in stings of other venomous fish.¹⁸

Catfish sting treatment is immediate immersion in hot water (no warmer than 113ºF) for pain relief. Catfish spines may penetrate the skin and break off. Sometimes, the spines can be located by routine radiographs. Occasionally, MRI is necessary to locate a foreign body. The wound should be explored and debrided. Retained catfish spines should be removed by a qualified practitioner. The puncture wound is left open. Treatment with prophylactic, broad-spectrum antibiotics and tetanus prophylaxis are indicated.

Disposition

Children with mild stings responsive to hot water soaks may be discharged after observation. Children not responsive to pain management may have a retained foreign body. Children envenomed by stonefish should be monitored in an intensive care setting. If it is available, antivenom administration is indicated in symptomatic patients.

Echinoderms are spiny invertebrates that include sea urchins, sea stars, starfish, sand dollars, and sea cucumbers. Of these, sea urchins most often cause medically significant envenomations. They are slow moving, colorful bottom dwellers found at various ocean depths (Fig. 135-9).

Pathophysiology

The spines or pedicellariae of sea urchins produce painful puncture wounds, swelling, and localized erythema.

Clinical Presentation

The spines can be up to 1-ft long in the needle-spined urchin (genus Diadema). They can easily puncture the skin, break off, and be retained. Their venom can cause local pain that may persist for days.

Management

Treatment is immediate immersion in hot water (no warmer than 113ºF), careful removal of pedicellariae and spines, and local wound care. Tetanus immunization and antibiotic prophylaxis are often indicated.^38,39

Disposition

Most sea urchin puncture victims can be discharged home with continued hot water soaks and antibiotic prophylaxis. If there is a retained foreign body, follow-up evaluation is prudent.

Sea snakes of the family Hydrophiidae are encountered throughout the Indo-Pacific region. The yellow-bellied sea snake (Pelamis platurus) (Fig. 135-10) has the widest distribution ranging from the Indo-Pacific to Africa to Central America. Sea snakes are air-breathing reptiles with venomous anterior fangs. They are among the deadliest snakes in the world and may bite without provocation.^8,40 Most bites are associated with net fishing and inadvertent handling.

Clinical Presentation

The venom of the sea snake has neurotoxic, myotoxic, and nephrotoxic effects. Most sea snake bites are dry bites with little venom injected. With true envenomations, symptoms usually manifest within 30 minutes to 3 hours. Initial symptoms may include muscle spasms and trismus. Severe envenomations may result in acute neurotoxicity with rapid muscular and respiratory paralysis.

Management

Apply pressure immobilization technique by wrapping the involved extremity with a compression bandage with immobilization until the victim is brought to definitive care. Respiratory support may be required. A polyvalent antivenom from Australia is commercially available.¹⁸ Additionally, a monovalent antivenom designed for the Australian terrestrial tiger snake has been used successfully when the polyvalent sea snake antivenom is unavailable. If antivenom is administered, the patient should be closely monitored for signs of anaphylaxis and given appropriate doses of diphenhydramine, glucocorticoids, and epinephrine as needed.

Disposition

All documented and suspected sea snake envenomation victims should be monitored in an intensive care setting for possible airway management and antivenom administration.

For an overview of management of marine envenomations, see Table 135-1 and Fig. 135-11.