William A. Burke, MD is associate professor of medicine and section head, section of dermatology, department of medicine, East Carolina University, Greenville, N.C. A licensed pilot, Burke is a member of a number of professional societies, including the Seaboard Medical Association. He has written numerous articles and has lectured extensively on various aspects of dermatology.
May 1996
Commonly encountered stinging hazards include jellyfish, fire coral, hydroids, sea anemones, sea urchins, toxic sponges, cone snails, marine worms, sea slugs and a variety of stinging fish, including catfish, stingrays, lionfish, toadfish and scorpionfish. Cutting and penetrating injuries are less common but may be due to moray eels, bluefish, sharks, barracuda, surgeonfish and needlefish. Dermatitis may be due to algae (red tide dermatitis and sea bather's eruption) or other micro-organisms (sea lice). Although staphylococci and streptococci account for most infections from an aquatic environment, one must be on the lookout for more unusual organisms, such as Erysipelothrix rhusiopathiae Mycobacterium marinum, Aeromonas hydrophila and the halophilic vibrios.
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Although people are most concerned about shark bites, these are actually rare. I am more concerned about common injuries, such as those by the Portuguese man-o'-war and stingrays. The Portuguese man-o'-war has a blue float that is visible on the surface of the water; however, because the tentacles may be up to 30 long, the float may go unnoticed. Man-o'-war stings are common in the southeast United States. Stingrays can also cause a serious injury due to the venomous spine on their tails. There are about 1,500 stingray injuries per year in the United States. The spine is used defensively and most victims accidentally step on the ray, trapping it against the bottom.
Significantly different hazards are encountered in different regions. The largest diversity of sea creatures, including the hazardous ones, is found in tropical reef areas. However, the water clarity is generally excellent, and hazardous creatures are much easier to avoid. Swimming hazards, such as the huge lion's mane jellyfish, can occur even in icy Arctic waters, yet there the swimmer is well-protected from stings by a wet suit. Some genera vary by location, such as the larger and more dangerous Atlantic Portuguese man-o'-war, which has multiple tentacles, compared with the less dangerous, single-tentacled Pacific man-o'-war; or the more dangerous great barracuda found in the Atlantic Ocean compared with the related Pacific barracuda. Some regional differences escape rational explanations, such as the occurrence of poisonous sea snakes in the Pacific and Indian Oceans, yet their notable absence in the Atlantic Ocean and Mediterranean and Red Seas. The Australia-Asian area has a wide diversity of sea creatures, and swimmers here need to be aware of many dangerous animals.
Sea bather's eruption and Portuguese man-o'-war invasions are well-known problems following storms. Sea bather's eruption is an irritant dermatitis caused by toxins secreted by certain blue-green algae. The algae are broken into microscopic fragments by waves during storms. These small fragments are filtered out by one's bathing suit and secreted toxins cause a dermatitis under the suit. Unlike true jellyfish that have a motile bell, the motility of the Portuguese man-o'-war depends on a wind-driven sail atop its float. After severe storms, beaches may become littered with large numbers of man-o'-war. Until tentacles are completely desiccated, they still can cause a severe sting, even when on the beach.
Catfish have toxic pectoral and dorsal spines and are found in both fresh as well as salt water. These fish primarily cause injury when handled but also can be a problem if they are stepped on. Swimmer's itch is primarily seen in fresh and brackish water and is due to a cercarial flatworm that normally parasitizes waterfowl and aquatic snails. These microscopic worms burrow into exposed skin, and skin covered by a bathing suit is spared. Although quite pruritic, the infestation is self-limited and vigorous toweling after swimming is said to reduce the degree of infestation. Although the halophilic vibrios are usually encountered in salt water, other aquatic pathogens — E. rhusiopathiae, M. marinum, and A. hydrophila — are encountered in fresh water. In tropical freshwater regions, electric eels, electric catfish, freshwater stingrays and biting fish, such as piranha, can be encountered.
Coelenterates that have caused human fatalities include the Portuguese man-o'-war and the box jellyfish. Reportedly, envenomation by stonefish, blue-ringed octopus, sea snakes and cone snails has also been been fatal. Antivenom is available for stings from the box jellyfish, stonefish and sea snakes. Fatal fish bite injuries are usually due to shark attacks. Especially in immunosuppressed patients or those with liver disease, aquatic-derived infections due to A. hydrophila or the halophilic vibrios can be serious and possibly fatal. In particular, Vibrio vulnificus infection often presents as septic shock, and mortality approaches 40% to 60% even with treatment.
There are quite a few misconceptions, and some may even cause harm. Examples of commonly advocated remedies for jellyfish stings are flushing the involved area with gasoline, alcohol, urine or fresh water, applying meat tenderizer, or even rubbing the area with sand. I've used some of these in my younger days, and I know they don't work. Using fresh water, alcohol or any substance that changes the osmotic pressure of the stinging cells will cause an immediate discharge of the nematocysts and could send the victim into shock. Using vinegar to fix the cells is the preferred method for man-o'-war or box jellyfish stings, whereas a slurry of bicarbonate of soda is preferred for sea nettle stings. If nothing else is available, there is always plenty of ambient sea water to flush the affected area. Other misconceptions include: horseshoe crabs can sting, but they can't; aquatic and marine injuries don't need updated tetanus prophylaxis boosters, but they do; shark attacks are common, but they aren't; erysipeloid, known as fish poisoning, doesn't need to be treated, but it does; and sea lice is due to a single genus of sea creature, but it is actually a common term used to describe a variety of clinical presentations due to many organisms.
It is not uncommon for a patient not to know what caused the injury. The clinical presentation can sometimes be a clue to diagnosis. Look for a laceration, puncture wound or rash, and the distribution and pattern, for example, linear papules or vesicles on exposed skin as in a jellyfish sting, or a cluster of multiple black-colored punctures as in a Diademasea urchin injury. With envenomation syndromes, pain is commonly out of proportion to the injuries seen, and there may be systemic manifestations. Sometimes an encounter with a marine creature can lead to very serious sequelae yet remain undiagnosed.
Vinegar soaks are the first aid treatment of choice for man-o'-war and box jellyfish stings, whereas a bicarbonate of soda slurry may be better for sea nettle stings. This is followed by removal of tentacles using a towel or a knife blade, and then flushing the area with ambient sea water. Mild stings from a variety of organisms, including sponges, hydroids, sea anemones, fire coral or marine worms, often can be treated symptomatically. The same is true for dermatitis due to sea lice, red tide dermatitis or sea bather's eruption. Swimmer's itch and pruritic delayed reactions due to coelenterates or echinoderms often respond to topical or systemic corticosteroids. With puncture injuries from sea urchins or the crown-of-thorns starfish, try to remove the spines, although they crumble easily. Soaking the affected area with hot water (110°F to 115°F) mixed 1:1 with vinegar is helpful. Spines can be visualized on x-ray as needed. Hot water is also useful in treating most marine envenomations as the venom proteins are generally quite heat labile. Lacerations from corals, stingrays, crab pinches or fish bites need to be vigorously cleansed after bleeding is controlled.
Peculiar aquatic infections need to be considered in patients who have injured themselves in the water. Erysipeloid is easily treated with penicillin, erythromycin, ampicillin or a first-generation cephalosporin, but is notably resistant to vancomycin. In children, M. marinum infection is generally treated with trimethoprim-sulfamethoxazole, whereas minocycline is the drug of choice in adults.
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