Venomous marine animals produce venom in specialized glands. The venom can then be applied to or injected parenterally into other organisms using a specialized venom apparatus. Venom is not a pure substance but a mixture of mainly protein and peptide toxins. The effect of a specific toxin depends on its site of action; it may be neurotoxic, hemotoxic, dermatotoxic, cytotoxic, or myotoxic. Unlike thermosTable ingestible seafood poisons, marine venoms are typically high-molecular-weight, heat-labile proteins.23
STINGRAYS AND VENOMOUS FISH
All stingrays' tails house venomous spines.15 Inflicted lacerations allow the injection of venom. Stingray injuries cause immediate intense local pain that may radiate and last for many hours. There is often significant bleeding depending on the site of injury, and the wound may be erythematous or dusky. Systemic effects are uncommon but have been reported and relate more to the systemic response to severe pain. Submerging the affected extremity in hot water between 110°F (43.3°C) and 114°F (45.6°C) can denature the venom protein and provide pain relief within 10 to 30 minutes.24,25 Topical lidocaine can be applied for additional pain relief.
Venomous fish are found in tropical and, less commonly, temperate oceans and private aquariums. The important venomous fish include stonefish, weeverfish, scorpionfish, and lionfish. The effects of the stings range from severe with stonefish to minimal with some types of catfish and other fish with nonvenomous spines.16,26
Stonefish (Synanceia species) and scorpionfish (Scorpaenidae) occur throughout tropical and warmer temperate oceans from the central Pacific, west through the Indo-Pacific, to the East African coastline. They are a diverse group of fish, with differing habitats, swimming patterns, and ability to camouflage.16,26 The venom apparatus varies among species but most have 5 to 15 dorsal spines. Stonefish are stationary bottom dwellers usually frequenting shallow water.
Clinical effects are characterized by immediate severe and increasing local pain, which may radiate proximally. Untreated, the pain typically peaks at 30 to 90 minutes and persists for 4 to 6 hours, but this varies considerably for different fish. The wound site usually has significant local edema and erythema (Figure 213-2). Nonspecific systemic effects such as sweating, nausea, vomiting, and even syncope may occur. Extensive tissue necrosis is not seen unless a secondary infection develops.
Significant edema and erythema of the right hand after stonefish sting to the thumb. [Photo contributed by Anthony Morocco, MD.]
Weeverfish (or weaverfish) are all saltwater fish and are the most venomous fish in the temperate zone. They are found in the Mediterranean and European coastal areas and are bottom dwellers that sting when stepped on. Their five to seven envenoming dorsal spines can penetrate leather boots, producing pain severity similar to stonefish injuries. Wounds may eventually necrose.
TREATMENT OF VENOMOUS FISH AND STINGRAY INJURIES
Irrigate the wound immediately, and remove any visible pieces of the spine or integumentary sheath. Control bleeding and immerse in hot water immersion as soon as possible (Table 213-3). During the hot water soak, the wound can be explored and foreign material removed. Provide oral or parenteral analgesics as needed. The wound can also be infiltrated with lidocaine without epinephrine, or a regional nerve block can be applied to help control pain.
TABLE 213-3Early Treatment of Marine Envenomations ||Download (.pdf) TABLE 213-3 Early Treatment of Marine Envenomations
|Organism ||Detoxification ||Further Treatment |
|Penetrating Envenomations |
|Catfish, lionfish, scorpionfish, stingray ||Hot water immersion*, topical lidocaine || |
Usual wound care†; irrigate with seawater or normal saline (NS)
Observe for development of systemic symptoms
Carefully assess for deep penetration from stingray spines
|Stonefish, weeverfish ||Hot water immersion*, topical lidocaine || |
Usual wound care†; irrigate with seawater or NS
Stonefish antivenom for severe systemic reaction (CSL Ltd., Melbourne, Australia); be prepared to treat anaphylaxis
|Sea snake ||— || |
Polyvalent sea snake antivenom (CSL Ltd., Melbourne, Australia) for systemic reaction; be prepared to treat anaphylaxis
Supportive care; observe for 8 h for myotoxicity and neurotoxicity; may need intensive care unit (ICU) care
|Blue-ringed octopus ||— ||Pressure immobilization; flaccid paralysis and respiratory failure can develop in minutes. Provide respiratory support and ICU care |
|Cone snail ||— ||Pressure immobilization; observe for paralysis and respiratory failure; supportive care |
|Sea urchin and starfish ||Hot water immersion*, topical lidocaine ||Explore wound and remove any spines, tufts, or pincers |
|Fireworms ||Topical 5% acetic acid (vinegar) || |
Consider topical corticosteroids
|Nonpenetrating Envenomations |
|Fire coral, hydroids ||Irrigate with seawater or saline ||Topical corticosteroids for itching |
|Portuguese man-of-war, bluebottle jellyfish || |
Hot water immersion*, seawater irrigation, topical lidocaine
Remove tentacles and nematocysts
Topical corticosteroids for itching
Observe for development of systemic symptoms
|Box jellyfish (Indo-Pacific Chironex species and Australian Carukia species) || |
Hot water immersion*
Irrigate with saline or seawater
Topical 5% acetic acid (vinegar)‡
Remove tentacles and nematocysts
Topical corticosteroids for itching
Observe for development of systemic symptoms
|Irukandji syndrome (Australian, Carukia species) || |
Irrigate with saline or seawater
Hot water immersion*
Remove tentacles and nematocysts
Administer Chironex antivenom; be prepared for anaphylaxis
Magnesium for cardiac arrest
Parenteral opioids for pain
Once pain is controlled, cleanse the wound using an aseptic technique, reexplore and remove foreign material, and debride necrotic tissue. Obtain soft tissue imaging when possible, to visualize retained foreign material.
The conclusions of the few study series involving venomous fish stings and the experience of aquarium workers are that most injuries are minor and do not require antibiotics.26 Although some authors routinely recommend antibiotic prophylaxis, the majority do not unless the wound is large or there is considerable foreign material. This situation is more likely with stingray wounds, which have the greatest potential to cause necrosis and infection. Prevention of infection by careful cleaning of the wound and debridement, if required, is more important. An antivenom exists for stonefish envenomation (CSL Ltd., Melbourne, Australia) and should be used in cases of severe systemic reactions to stonefish and possibly other venomous fish.27,28 Although it is registered for IM and IV administration, IV is more likely to be effective, based on experience with other antivenoms. The antivenom is prepared from horse serum, so be prepared to treat anaphylaxis.
There are numerous species of sea snakes that are closely related to terrestrial elapids, all of which are venomous. They occur in the tropical and warm temperate Pacific and Indian Oceans. None are found in the Atlantic Ocean, the Caribbean, or North American coastal waters, except Hawaii. Probably the most important species medically is the beaked sea snake (Enhydrina schistosa), which has caused fatalities in Southeast Asia.
Sea snakes can be distinguished from land snakes by their flat tails and valve-like nostril flaps and from eels by the presence of scales and the absence of gills and fins. The venom apparatus consists of two to four short, hollow maxillary fangs, and a pair of associated venom glands. About 20% of bites cause significant envenomation, and up to 40% of these are potentially fatal without treatment. The venom of sea snakes contains neurotoxins and myotoxins; one tends to dominate the clinical features. However, there are no toxins that affect coagulation.
Bites are typically painless and may go unnoticed. Symptoms typically become apparent 30 minutes to 4 hours after the bite. The first complaint is usually related to myotoxicity, with severe myalgia and nonspecific muscle weakness. Other symptoms include nausea, vomiting, and malaise. The muscle pain may become so severe that movement is limited, which is typified by trismus that develops in the jaw. Immobility secondary to pain should be distinguished from weakness or paralysis caused by neurotoxicity. Rhabdomyolysis and secondary renal failure develop in more severe cases, which may be complicated by hyperkalemia. In some sea snake envenomations, neurotoxicity has been reported without myotoxicity, with ascending flaccid or spastic paralysis accompanied by ophthalmoplegia, ptosis, facial paralysis, and pupillary changes. Death is most commonly a result of respiratory failure.
Diagnosis of a sea snake bite is based on the combination of snake identification and the presence of a puncture bite wound that was initially painless and occurred in or near the water. Suspect envenomation if severe myalgia develops. The presence of myoglobinuria and an elevated creatine kinase level is also typical, indicating rhabdomyolysis. Neurotoxic symptoms are rapid in onset and usually appear within 2 to 3 hours. If no symptoms develop by 6 to 8 hours, envenomation is unlikely to have occurred.
First aid treatment is pressure immobilization of the affected limb.29 Elastic bandages are preferred.30 Administer polyvalent sea snake antivenom (CSL Ltd., Melbourne, Australia) for systemic envenomation.28 The antivenom is made from horse serum, so be prepared to treat anaphylaxis. Intensive supportive care and monitoring of renal, metabolic, and respiratory functions are critical.
Injuries from the octopus or squid are unusual. All octopuses have venom, but the only dangerous octopus is the blue-ringed octopus. The venom tetrodotoxin, introduced by a bite, causes respiratory arrest within minutes. Treatment is supportive. Pressure immobilization at the bite area is the recommended first-aid treatment.
The bite of the Australian blue-ringed octopus (Hapalochlaena species) has caused at least two deaths. The saliva of the octopus contains tetrodotoxin and produces effects clinically identical to those of tetrodotoxin poisoning seen most commonly with puffer fish ingestion.31,32 Octopus bites typically occur on the upper extremity, almost always when the animal is picked up (Figure 213-3). The bite causes small, painless puncture marks and many go unnoticed. In most cases, no symptoms develop or only mild local numbness and paresthesia occur. In more severe envenomations, vomiting and progressive flaccid paralysis with eventual respiratory failure may begin within 10 minutes of envenomation.33 Wrap the limb with a lymphatic occlusive bandage to provide pressure immobilization until definitive care is reached. Treatment is supportive, with mechanical ventilation as required, and full recovery usual occurs over 1 to 5 days. No antivenom or antidote is available.
This acute octopus bite (A) was initially treated with ciprofloxacin, but persisted with a scab (B) and regional adenopathy for several months. After treatment with doxycycline, adenopathy resolved, but a chronic nonhealing ulcer remained despite multiple specialty consultants. [Photo contributed by Steven Whelpley, MD.]
Cone snails have intricate shell patterns, making them attractive to handle. Cone snails are predators that feed by injecting a potent mixture of neurotoxins using detachable, dart-like radicular teeth. Stings by cone snails are very rare. Most stings occur after prolonged contact with the shell or when breaking the shell. With significant envenomation, local pain is followed immediately by local numbness, which quickly spreads from the extremity to the trunk and then to the head and neck region. Partial paralysis develops within 30 minutes, progressing to complete voluntary muscle paralysis and respiratory failure. Mortality following Conus geographus envenomation may be as high as 65%.34 Less severe envenomations cause muscle pain, partial paralysis, or ataxia, or in mild cases only local effects. Treatment is pressure immobilization with a lymphatic-occlusive bandage until definitive care is reached.
Sea urchins are found in all oceans, and most sea urchins have solid nontoxic spines. Injury from the spines causes localized pain, which is exacerbated by pressure, even if there are no retained spines in the wound35 (Figure 213-4). If a spine enters a joint, it may cause severe synovitis. Wounds from black sea urchin spines may leave a black discoloration of the skin. Contact with the venomous spines causes immediate, intense burning pain, with erythema, swelling, and often bleeding of the skin surrounding the puncture sites. The acute pain usually subsides over hours. Secondary infection and granuloma formation from remaining spine fragments are well-described delayed effects. Systemic features have been reported rarely, often when multiple spines are involved, but may be due to severe pain.
Sea urchin sting in the foot showing the entry sites. [Used with permission of Vidal Haddad Jr., MD, PhD.]
Some starfish have surface spines, tufts, or pincers. The crown-of-thorns starfish (Acanthaster planci) can be found on most reefs in the Indo-Pacific region and has caused outbreaks of envenomation in Japan and Australia.1 Crown-of-thorn starfish are covered with sharp, rigid spines that can passively deliver a variety of substances when they penetrate skin. This includes venom produced in special glandular tissue, mucus, bacteria, and dermal tissue. Injury by the spines causes severe burning pain, often greater than expected for the mechanical injury, and lasts 1 to 2 hours. Other local effects include bleeding, erythema, and mild edema. In more severe cases, particularly with multiple punctures, the wound may become dusky or discolored. Pruritus and persisting edema can occur, perhaps as a result of allergy. Systemic effects are uncommon but may include paresthesias, nausea, vomiting, lymphadenopathy, and muscular paralysis.1,6
Treatment is immediate immersion in hot water to tolerance (45°C [113°F]) for 30 to 90 minutes or until pain is relieved. Topical or locally injected lidocaine can provide additional pain relief. Give analgesics. Remove retained spines or tufts as well as possible, without causing more tissue injury. Soft tissue radiographs, US, or MRI may be helpful in locating retained spines. US may be particularly helpful in identifying radiolucent fragments of sea urchin spines.19 Arrange follow-up, because further surgical removal of spines may be required if there are ongoing symptoms. Spines in joints require immediate orthopedic consultation.
FIREWORMS OR BRISTLEWORMS
Fireworms, or bristleworms, are segmented worms covered with cactus-like bristles that can penetrate the skin. These bristles easily detach in the skin and can be difficult to remove. Envenomation causes intense inflammation with a burning sensation and erythema. Untreated, the pain generally resolves within a few hours, but erythema may last for 2 to 3 days. Bristles should be removed with forceps or adhesive tape. Vinegar (5%) may be applied topically. The inflammatory response may require a course of corticosteroids.
Hydroids are colonies of tiny jellies attached to a feather-like or seaweed-like base. They are abundant on seaweed, reefs, pilings, floating docks, or lines. Coastal storms can break off feather hydroid branches and cause infestation of a local swimming area. Fire corals look like corals, are often mistaken for seaweed, and are small brush-like growths on rocks and coral itself. Contact with nematocysts or stinging threads results in an immediate sting after even a superficial brush contact, followed by itching pain, associated with the development of painful wheals and urticaria after 30 minutes. The welts may last for up to a week but leave no permanent mark. With more extensive exposure, blistering and a hemorrhagic and zosteriform reaction can occur. Lesions crust over after a few days. Vinegar can inhibit nematocyst discharge. Pain relief can be provided with analgesics. Treat itching with topical steroids.
There are many types of jellyfish, but the most important groups affecting humans are the Portuguese man-of-war or bluebottle jellyfish, the box jellyfish, and those jellyfish causing Irukandji syndrome.
Jellyfish are characterized by their unique stinging nematocysts34 (Figure 213-5), which number in the thousands and are found mainly on the tentacles, but also in lesser numbers on the body or bell. The nematocyst contains a minute dose of venom, in some cases highly potent, and a harpoon-like mechanism. A physical or chemical stimulus triggers the rapid release of a hollow, sharply pointed, threadlike tube from the nematocyst, which penetrates the skin and delivers venom subcutaneously. There are a number of genera causing local and systemic reactions, off the coasts of Russia, Japan, Brazil, Uruguay, and Argentina—all with similar toxic effects.
Nematocyst. Photomicrograph of anemone tentacle showing discharged nematocysts. Note venom ejected upon discharge. [Used with permission of Destin Sandlin, Smarter Every Day, full video may be viewed at: https://www.youtube.com/watch?v=7WJCnC5ebf4.]
The clinical features of jellyfish envenomation vary in severity. The severity depends on the venom dose, the marine species, and the victim (age and size). Mild envenomation results in bothersome acute skin reactions, with immediate stinging pain and erythema or wheal formation at the site. Lesions usually resolve spontaneously over days to a couple of weeks, with occasional postinflammatory hyperpigmentation.
Treatment of jellyfish stings is not well studied, and results are often conflicting. A treatment helpful for one species may worsen effects from another species. Irrigation with seawater to remove nematocysts and hot water immersion and application of topical lidocaine appear to be the most universally beneficial treatments. Other applications, such as sodium bicarbonate or vinegar, may worsen stinging from some species.
PORTUGUESE MAN-OF-WAR AND BLUEBOTTLE JELLYFISH
This group of jellyfish (Physalia species) has a large gas-filled float, which suspends multiple tentacles. The nematocysts are found on the tentacles but not on the float. Physalia species are the most widely distributed jellyfish and are responsible for thousands of human envenomations in Florida, parts of Asia and Africa, Australia, and Western Europe.1,2,36 All species occur in swarms in shallow water and usually cause stings in the surf or are washed up on the shore. Nematocysts from fractured tentacles may remain active for months.
The Portuguese man-of-war is a multitentacled jellyfish common in the Atlantic, with tentacles that can be as long as 30 m. The bluebottle jellyfish is smaller and single-tentacled and found commonly in Australia and Hawaii.
Stings from Physalia species cause immediate, intense pain that often fades over an hour but may persist for many hours, particularly with larger specimens. The sting causes a characteristic linear erythematous eruption, classically referred to as a "string of pearls" pattern.35 Respiratory distress and death have been reported following Physalia envenomation, and delayed effects have been reported in rare instances.36,37
Treatment is to first wash the area with seawater and then immerse in hot water, as the venom is heat labile. In general, vinegar is not recommended for Physalia stings. Remove tentacles and nematocysts by scraping the skin with a sharp object (e.g., razor or credit card) or by applying adhesive tape.38 If adhesive tape is used, the adherent nematocysts can later be identified.
There is no specific antidote for Physalia envenomation, and care is supportive.
BOX JELLYFISH AND IRUKANDJI SYNDROME
The box jellyfish is the most dangerous jellyfish and includes two important members: the Indo-Pacific box jellyfish (Chironex fleckeri) and the Australian jellyfish (Carukia barnesi) that causes Irukandji syndrome.39,40 Box jellyfish are also found in the Philippines, Japan, and the U.S. Atlantic coast. The Hawaiian box jellyfish (Carybdea alata) causes numerous stings to beachgoers in Hawaii, although no deaths have been confirmed from this organism.41
The Indo-Pacific box jellyfish (Chironex) has been described as the world's most venomous animal.42 It has caused over 80 deaths in the past century.43 The exact mechanism of toxicity and toxins involved in death—which occurs rapidly, often within 20 minutes—remains unclear, but a primary cardiotoxic role is likely.42 Severe reactions or death can occur following skin contact with tentacles, especially in children.39,44 However, the vast majority of stings are mild to moderate, consisting of skin welts and immediate, sometimes severe pain.39 The toxic skin reaction may be quite intense, with rapid formation of wheals, vesicles, and a darkened reddish brown or purple whip-like flare pattern with stripes 8 to 10 mm wide. With more severe stings, blistering occurs, and superficial necrosis develops after 12 to 18 hours. Severe box jellyfish stings cause a pathognomonic crosshatched pattern, classically referred to as a "frosted ladder" pattern (Figure 213-6). Following the acute toxic reaction, a delayed hypersensitivity reaction occurs in approximately 60% of cases, with papular urticaria at the sting sites.39,45
Box jellyfish sting. This 24-year-old woman was snorkeling off of Koh Tao, Thailand, when she was stung by a box jellyfish 15 minutes prior to this photograph being taken. She presented with severe extremity pain and chest tightness. [Photo contributed by Sittidet Toonpirom, MD, and Rittirak Othong, MD.]
The Australian jellyfish (C. barnesi) causes the Irukandji syndrome.40 The sting initially causes mild local effects with localized pain and erythema. Approximately 20 to 30 minutes later, severe generalized pain in the abdomen, back, chest, head, and limbs develops. The pain is usually associated with systemic signs of catecholamine excess, including tachycardia, hypertension, sweating, piloerection, and agitation. In severe cases, cardiogenic shock with pulmonary edema and serum troponin elevation occur.40,44
Treatment Treatment consists of deactivation of attached nematocysts, tentacle removal, reversal of venom effects if possible, and symptomatic and pain relief. All victims with systemic signs or symptoms should be observed for ongoing envenomation or delayed reactions (Table 213-3).
Irrigate with seawater or normal saline to deactivate undischarged nematocysts. After deactivation, visible tentacles can be removed. Do not irrigate with freshwater because the hypotonic solution is thought to stimulate nematocyst discharge. Best methods for removal are scraping the skin with a sharp object (e.g., razor or credit card) or application of adhesive tape.38 If adhesive tape is used, the adherent nematocysts can later be identified. Treat with hot water immersion (111°F [43.3°C] to 114°F [45.6°C]) and apply topical lidocaine.46
Effective topical decontaminants appear to be species specific.46,47 Because the species is often unknown, the geographic location of the envenomation guides decontamination. In Indo-Pacific waters, particularly those surrounding Australia, nematocyst deactivation therapy with 5% acetic acid (vinegar) is recommended,43,48 and 5% acetic acid is the first-line management recommendation by the Australian Resuscitation Council.43,49
Treatment for severe Chironex envenomation (Irukandji syndrome) consists of standard resuscitative measures and administration of sheep-derived antivenom specific for C. fleckeri (CSL Ltd., Melbourne, Australia).39 Be prepared to treat anaphylaxis. Fatalities despite antivenom administration may be related to the rapidity of onset of cardiovascular collapse after Chironex envenomation.27 Therefore, antivenom should be administered IV as early as possible. The initial dose may be repeated if there is no clinical response, and some clinicians recommend three or more doses in severe envenomations associated with cardiovascular collapse.44 Magnesium improves outcome in animal studies and should be considered in refractory cases of severe Chironex envenomation with cardiac arrest.40,45
Severe generalized pain in Irukandji syndrome requires titrated IV opioid analgesia, often with large and repeat doses. Magnesium bolus and infusion have been used for treatment of the pain and hypertension associated with Irukandji syndrome.45,50 However, adverse effects due to hypermagnesemia have been reported, and the treatment has not been as effective as originally suggested.50 All patients should have an ECG and troponin testing on admission, and echocardiography is useful in patients with myocardial involvement. Pulmonary edema should be managed with oxygen supplementation, positive-pressure ventilation, and inotropes
In waters surrounding the United States, application of 5% acetic acid solutions to tentacles from Chrysaora species appear to increase nematocyst discharge.51,52 For Chrysaora or Cyanea, a slurry of baking soda (sodium bicarbonate) is thought to be effective. Traditionally, acetic acid solutions were thought to deactivate North American Physalia species nematocysts.52 However, one review of North American and Hawaiian jellyfish envenomation management has questioned the use of acetic acid, concluding that "vinegar may not be an ideal agent because it causes pain exacerbation," but may be considered in Physalia species envenomations, whereas "hot water and lidocaine appear more universally beneficial in improving pain symptoms and are preferentially recommended."46 The venoms are heat labile, and heat reduces toxicity in most jellyfish envenomations.36,41,47