marine envenomations cover

Marine Envenomations: Recognizing and Managing Sea Creature Stings

Marine envenomations are an uncommon but important consideration in water sports including swimming, diving, scuba, fishing, surfing, wakeboarding and others. They occur predominantly in tropical waters. Most envenomations occur not as an attack but act of self defense when an animal perceives danger. There are over 100,000 species, 100 of which are known to be poisonous. In general, marine envenomations are not well studied and thus many guidelines are based on case reports or case series.

In the united states, envenomations are most commonly seen in Jellyfish (31%), followed by stingrays (16%) venomous fish venomous fish (including lionfish, catfish, and others) (28%), and gastropods (6%). In the US, there are 1500 stingray bites annually and globally there are thousands of injuries with few fatalities [2, 3]. In general, marine venoms generally contain heat labile proteins which quickly denature with hot water. Although they will not be reviewed in detail remember to consider tetanus booster and antibiotics covering staph, strep and vibrio. We also will not spend too much time discussing analgesic options, of which there are many. If you have questions, always call the poison control center (800) 222-1222.

Nematocysts (Phylum: Cnidaria)

seabathers eruption marine envenomations

Image 1. Example of seabather’s eruption (courtesy of the Dr Andrew Schmidt)

Seabather’s eruption. This a non-specific dermatitis secondary to nematocyst exposure. Symptoms include pruritic papules resembling insect bites in the distribution of swimsuit which often occurs during a shower after swimming in ocean as fresh water ruptures larvae. Treatment includes bathing the skin with acetic acid 5%, or lidocaine-containing first aid remedy. Swimmers should be careful to wash the swimsuit with hot water and detergent, then machine or sun dry

man o war marine envenomations

Image 2. Two examples of portuguese man-of-war

Portoguese man-of-war (Physalia physalis and Physalia utriculus). Found primarily in the Atlantic, Indian and Pacific oceans and stings common in southern US. Not a true jellyfish, formed by colonies of siphonophore with each unit a specialized animal of the same species. Tentacles grow up to 30m (atlantic), 3m (pacific) depth. Symptoms include local sharp pain immediately after the sting, followed by an erythematous maculopapular linear rash, local edema, and numbness. The rash improves at 24 hours, complete resolution by 72 hours. Complications are rare but include skin necrosis, cardiorespiratory collapse, and rarely death. There is no antivenom. Treatment consists of removing tentacles, preferably with forceps or gloved hand. The affected areas should be immersed in hot water (45°C) for 10–20 min preferred over local application of ice-packs for pain control [9]. Avoid using vinegar or methylated spirits (can increase nematocyst firing). Topical anesthetics can be considered after successful removal of all tentacle fragments. Use oral or parenteral analgesics if pain persists.

fire coral marine envenomations

Image 3. Two examples of fire coral

Fire corals. These have a worldwide distribution among reef crests and shallow waters (except hawaii). Symptoms include immediate pain and urticaria, sometimes progressing to hemorrhagic or ulcerating lesions. Pain resolves by 90 minutes, local symptoms by 72 hours. Less commonly more severe systemic symptoms include nausea, vomiting, muscle cramps, dyspnea, anxiety, abdominal pain, and headache. There is no antivenom. Treatment primarily revolves around applying acetic acid 5% (vinegar) to the skin. Consider steroid cream or an oral antihistamine for symptomatic relief and oral corticosteroids if severe.

box and irukandji jellyfish marine envenomations
Image 4. Box jellyfish (left) and Irukandji jellyfish (right)

Box Jellyfish (Chironex fleckeri). Sometimes referred to as sea wasp and marine stinger. Seen primarily tropical indo-pacific ocean however there are reports in the southeast united states as well. These occur most often during the Australian summer: 92% of the stings took place between October 1 and June 1 (i.e., stinger season). 83% of stings occur in shallow water (<1 m) [4] between 3-6pm and 8% of stung patients required hospitalization. Box Jellyfish sting is a medical emergency due to its potential lethality and should be treated as such. There are at least 67 deaths in Australia and most people die 20 minutes after sting. Up to 25% of people die, more than sharks.

Symptoms include itchy red maculopapular rash, burning pain, edema, and the classical ladder-rung pattern lesion. Complications of a ‘major sting’ can present as altered, somnolent, bradypneic, tachycardic, hypotensive. Additionally seen are cardiotoxic effect, nerve palsy, hemolysis, cardiopulmonary decompensation, shock, and death. Confirming exposure can be challenging. Look for the ‘cross-hatched ladder pattern’ lesion and you can identify nematocyst using blade and the sticky tape.
Treatment involves removing the tentacles ASAP to reduce the likelihood of lethal injury. Poor 4-6% acetic acid (vinegar) to prevent further stinging. Poor on the affected area for a minimum of 30 seconds. Note vinegar does not provide pain relief. This should be followed by a hot water shower as tolerated for 10 – 20 minutes. Wound care involves applying a compression bandage distal to proximal. Immobilize to help decrease muscle activation pumping venom proximally. This has been proven effective in venomous terrestrial snakes in Australia [15]. Be sure to address pain with ice packs, topical, oral and parenteral analgesics. There is an antivenom (chrionex), or CSL Antivenom, which is effective if given in the first hour or if there are any signs of cardiorespiratory collapse. More experimental is Verapamil (mixed-to-positive evidence) to reverse cardiovascular response to toxin, Beta blockers, magnesium sulfate (no great evidence).

Irukandji jellyfish (Carukia barnesi). Much smaller jellyfish, ranging from 3 to 19 mm seen in northern and western coasts of australia. Initial Symptoms are simply a wheal, local erythema at the sting site. Patients can go on to develop a phenomenon known as ‘Irukandji syndrome’ between 20m and 2hr after sting. Thought to be sympathetic nervous system stimulation presenting with sympathomimetic toxidrome. Symptoms include severe abdominal, chest, limbs, or back pain; generalized muscular pain, hypertension, tachycardia, vomiting, nausea, diaphoresis, piloerection, and local erythema. Complications include hypertensive crisis, hemodynamic decompensation with abnormal ECG and elevated troponins, cardiac failure, and death. Treatment consists of hot water shower as tolerated for 10–20 min, vinegar irrigation, antihypertensive therapy, magnesium sulfate i.v., and pain management (including local use of cold packs/ice and opiates). Do not use pressure immobilization bandages. There is no antivenom currently but ongoing research. Antihypertensives include phentolamine and magnesium sulfate should be considered [1, 8].

turtle grass and giant anemone marine envenomations

Image 5. Turtle grass (left) and giant see anemone (right)

Sea anemones (anthozoa). Their tentacles are loaded with stinging cnidocytes and secrete mucus that may contain cytolytic and hemolytic toxins, neurotoxins, cardiotoxins, and proteinase inhibitors. Symptoms include erythema and pruritus, petechiae, blisters, and ulceration at sting site. More rarely, systemic reactions include fever, chills, malaise, weakness, nausea, vomiting, muscle spasm, and syncope. Most cases resolve within 48 hours. Severe reactions may become indolent, leading to hyperpigmentation, hypopigmentation, or keloid formation [14]. Primary treatment is acetic acid 5% and symptom management.

“Stingers”/Penetrating Injuries

Stinger category is a reference to the mechanism of injury which in this case includes apparatus that punctures skin and delivers venom. Primary treatment is to remove stinger and evaluate for foreign bodies using XR or US. All stinger injuries should be treated with hot water immersion of 45 degrees celsius for 30 to 90 minutes. There is an antivenom to stonefish.
stringray MOI marine envenomations

Image 6. Typical mechanism of a stringray injury (left) and example of puncture wound in foot (right)

Stingrays (Family: Dasyatidae). Responsible for up to 2000 ED visits annually [13]. Seen in tropical warm waters and are found practically all over the world. Anatomically, they are a flat cartilaginous fish with caudal appendages harboring bilaterally retroserrate barbs and associated venom glands. Injury pattern has 2 phases: mechanical, due to barbed stinger at end of whiplike tail and venomous, due to gland at the tail base is injected into the victim. Venoms are variable and contain serotonin, 5’-nucleotidase, and phosphodiesterase. Toxin may induce peripheral vasoconstriction, bradycardia, tachycardia, atrioventricular block, and seizure activity.

Most injuries occur to the lower extremity as a result of stepping on one. Symptoms include pain and laceration at puncture site, nausea, vomiting, muscle cramps, barb lodged in skin, pain and swelling peaks at 60 minutes lasting up to 48 hours. Lacerations can become dusky with local hemorrhage and necrosis. Complications are more typically seen if torso injury including hypotension, dysrhythmia, arterial lacerations, thorax, and spinal cord trauma, nausea, vomiting, muscle cramps, syncope, arrhythmias. Most famous death is Steve Irwin who was killed by a penetrating injury to the chest. There is no antivenom. Treatment includes hot water immersion as tolerated (30-90 minutes), systemic and local analgesia, and plain films to evaluate for FB. FB removal; if lodged in chest should be treated like torso laceration and removed in OR. Tetanus and prophylaxis with antibiotics.
stonefish marine envenomations

Image 7. A stonefish.

Stone fish (Family: Scorpaenidae). Most venomous of the spine fish, venom comparable to potency of cobra venom. Resides in the Indopacific ocean and can grow up to 38 cm in length and weigh 1.5 kg. It’s body is covered in spines that release venom from mechanical pressure (i.e. someone steps on it). Symptoms include severe pain and edema at the site of sting, headaches, severely painful cyanotic puncture, wound, necrotic ulceration. Complications include weakness, syncope, dyspnea, hypotension, and hallucinations, altered mentation, fever, nausea, vomiting, seizures, paralysis, heart block, heart failure, pulmonary edema, death can occur within 6 hours.

Treatment begins with CSL Stonefish antivenom. All spines should be removed and hot water immersion as tolerated 30-90 minutes. Treat pain with NSAIDS, local and systemic analgesia. Debridement if needed or deeply penetrated spine. Consider prophylaxis with antibiotics, tetanus and observe 6-12 hr.
scorpion fish and lion fish marine envenomations

Image 8. A scorpion fish (left) and lion fish (right)

Lionfish & Scorpion fish (Family: Scorpaenidae). Venom is weaker than stonefish. The scorpion fish is second most toxic, found in the coastal waters of the Atlantic Ocean (usually Brazil, Uruguay, and Argentina) and is understudied fish due to its limited global distribution [12]. The lionfish is the 3rd most toxic spine fish and injury often occurs to the hands of people handling fish. Note the catfish is likely the most common but far less poisonous and thus under-reported. Symptoms include sharp, intense, throbbing pain at the site of injection which can radiate, peaks at 60-90 minutes. Symptoms can be broken down into three grading categories. First is mild with erythema, pallor, ecchymosis or even cyanosis are the first events that present, and result from the increased capillary permeability. Second is vesicle formation, as an effect of the toxins. Finally, one can see local necrosis observed within days, which is considered a grave complication and requires debriding. Treatment is the same as the stonefish except there is no antivenom.

sea urchin marine envenomations

Image 9. Two examples of sea urchins.

Sea urchins. They have globular bodies covered by calcified spines either rounded at the tip or hollow and venom-bearing. There are many species with various venoms including steroid glycosides, hemolysins, proteases, serotonin, and cholinergic substances. They typically present with painful puncture wounds with severe local muscle aching lasting up to 24 hours. Frequently, spines break off into the victim causing granuloma formation or synovitis. Systemic symptoms include nausea, vomiting, paresthesias, weakness, abdominal pain, syncope, hypotension, and respiratory distress. Secondary infections are common. Chronically, patients may develop granulomas. Treatment includes hot water (45°C) immersion and irrigation and exploration of only superficial wounds. If concerned, considered operative irrigation especially with joint involvement. Note that the spines are hard to remove and can “tattoo” the skin making it hard to tell if there is a retained foreign body.

crown of thorns starfish marine envenomations

Image 10. Two examples of the crown of thornes starfish

Star fish. The crown-of-thorns starfish (Acanthaster planci) is particularly venomous and produces a toxic slime that coats the spines. Its venom is hemolytic, myonecrotic, hepatotoxic, and anticoagulant. Initial symptoms include puncture wounds with immediate pain, bleeding, and edema. Wounds can become dusky and tenosynovitis may develop. Multiple punctures can cause systemic reactions with paresthesias, nausea, vomiting, lymphadenopathy, and paralysis. In most cases, pain resolves in 30 minutes to 3 hours. Retained spines can cause granulomas. Treatment includes hot water (45°C) immersion and irrigation and exploration of only superficial wounds.

cone snail

Image 11. The cone snail.

Cone shells/snails (Conus geographus). Their venom gland, teeth at end of proboscis (nose) and contains a conotoxin or neurotoxin that acts as a neuromuscular blockade which blocks potassium, sodium and calcium channels. Initial symptoms include severe pain at the site of sting, muscular paralysis. Complications include palpebral ptosis, speech difficulty, and swallowing impairment, and eventually respiratory arrest in occurs as fast as 40 min up to 5 h and typically lasts 12 to 36 hours. 50 deaths reported in the literature with a mortality rate as high as 25% [10].

There is no antivenom. Remove spine initially, which may require verification with XR or US. Place affected body part in hot water (45°C) immersion for up to 90 minutes or until pain relief. Immobilize extremity with pressure dressing. Consider intubation in the field if any evidence of neuromuscular blockade as these patients can rapidly decompensate. In the hospital, spine should be removed. Consider edrophonium (acetylcholinesterase inhibitor) and narcan (reverse hypotension).


blue ringed octopus

Image 12. Two examples of the blue ringed octopus.

Blue Ringed Octopus (Hapalochlaena lunulata). This animal is seen in shallow waters throughout Indo-Pacific oceans. Injury typically occurs when picked up out of the water by humans. They carry a tetrodotoxin which inhibits voltage gated sodium channels leading to paralysis. Symptoms can include flaccid paralysis, hypotension and less commonly respiratory failure and death. There is no antivenom. Treatment is generally supportive including mechanical ventilation if necessary. The limb should have a pressure bandage to minimize toxin spread. Most individuals can expect complete recovery in 2 – 4 days.

mexican beaded lizard and gila monster

Image 13. The Mexican beaded lizard (left) and Gila monster (right)

Lizard bites (Helodermatidae). Caused by either the mexican beaded lizard or gila monster, both of SE US, Mexico and Central America. Venom delivered by the bite from glands in the lower jaw. Generally causes localized, rarely systemic effect. Note teeth can be left behind in wound as a foreign body and nidus for infection. Symptoms include crush and puncture wounds, local erythema and pain. Much less commonly, systemic features including weakness, hypotension, diaphoresis. Treatment is mostly supportive and includes removal of the animal, imaging to identify foreign bodies, irrigating copiously, tetanus and prophylactic antibiotics.

sea snake

Image 14. The sea snake.

Sea snake (family Hydrophiidae). These are known to inhabit tropical Pacific and Indian oceans. Their venom is a neurotoxins acting at the acetylcholine receptor, and hemolytic and myotoxic compounds that cause muscle necrosis, hemolysis, and renal tubular damage. Approximately 80% of bites do not result in envenomation due to small, easily dislodged fangs. Initial symptoms include painless pinhead-sized fang marks and roughly 30-60 minutes later, muscle pain and stiffness, nausea, vomiting, ascending paralysis, respiratory failure, muscle necrosis, renal failure. There is an antivenom which reduces mortality rate to 3%, it is as high as 25% if not receiving antivenom. Apply a pressure immobilization dressing, maintain airway and breathing and admit to hospital. These patients require close monitoring of electrolytes and urine out as they may develop rhabdomyolysis, renal failure and hyperkalemia.

Read More:


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