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Travel Health Journal

Photo of jellyfish by Wopke, Pexels

Stings and bites: Preventing marine injuries

Nothing says ‘vacation’ quite like fun on the water.

Beachcombing, swimming, snorkelling, diving, wading, and watersports are common activities that can bring you in contact with marine animals. Skin infections, bites, and stings resulting from contact with marine life are some of the most common injuries affecting travellers to island and coastal destinations.  By some estimates, up to 150 million jellyfish stings occur worldwide every year. When you’re in the water, you can prevent injuries by being informed about local marine life and water conditions.

Stings, bites, and punctures from marine animals

There are three types of injuries associated with marine animals:

  1. Contact toxins – stings caused by jellyfish, coral, sponges, and sea urchins
  2. Injected toxins – envenomation caused by stingrays, scorpionfish, and cone snails
  3. Bites by predators like barracuda, moray eel, sea snakes, and sharks

Marine animals typically only sting or bite humans when touched or threatened. Keep a respectful distance from any marine life you encounter and avoid touching coral and sponges.

Preventing marine injuries

Marine injuries often occur when people step on stinging or biting animals in shallow water.

  • Find out which marine animals are common in the area. Do jellyfish or stingrays live in these waters? What about fire coral or sea urchins?
  • Watch your step: Always wear protective water shoes when wading. Note that thin shoes offer little protection against animals with spines, like stonefish.
  • When beachcombing, only put your hands where you can see them and avoid putting your hands or feet under ledges where animals could be hiding.
  • Do not touch, feed, or engage with marine animals.
  • Pack a first aid kit and bring it to the beach.
  • Ensure that your routine immunizations are up-to-date, including protection against tetanus.

Injuries caused by marine animals vary in severity, from lesions, rashes, burning, itching, and pain on contact to vomiting, cardiovascular collapse, respiratory stress, and paralysis. Even small abrasions and cuts can cause infections as bacteria, viruses, or other pathogens enter the body. It’s important to keep wounds clean at all times.

It’s especially important for travellers with pre-existing conditions such as a weakened immune system, diabetes, kidney disease, liver disease, cancer, blood disorders, or HIV to be aware of the risks of infection when coming into contact with marine animals.

First aid for marine injuries

Different injuries require different treatments.

Some bites and stings are minor, treatable with first aid, and may not require medical attention. However, you may have to seek care to manage pain, remove stubborn pieces of coral or nematocysts, and for proper wound cleansing. For puncture wounds, it is also prudent to get a tetanus shot (even if you are up-to-date), as well as a prescription for corticosteroids and antibiotics to prevent infection. For example, infections from Mycobacterium marinum bacteria cause skin lesions while Vibrio vulnificus and Vibrio parahemolyticus can cause wound infections and gastrointestinal illness if ingested. Tell the health practitioner whether you were in fresh water or seawater. If your doctor sends a specimen to the lab, the lab may need to make adjustments to compensate for salt water.

Taking an antihistamine after coming into contact with toxin released by marine animals is also recommended to prevent an allergic reaction. Look out for developing symptoms of anaphylaxis, a severe and potentially life-threatening allergic reaction to the toxin. Seek emergency medical care if the person has trouble breathing, has a change in awareness, or becomes unconscious.

Injuries from contact toxins

In general, injuries caused by jellyfish, sponges, coral, fire coral, anemones, and sea urchins cause skin redness, swelling, rash, burning, itching, and pain on contact. For example, if left embedded in the skin, coral can cause pain and irritation for weeks afterward. Note that anemones, fire coral, and jellyfish release nematocysts (barbed and coiled threads) into the skin, making the injury very painful. To deactivate the nematocysts, always rinse with seawater or salt water followed by liberal use of vinegar.

Below are quick first aid tips for common marine injuries. It’s important to seek medical care to ensure proper follow-up to first aid provided.

  • Sponges – Rinse and dry, lift spikes with adhesive tape, apply a topical corticosteroid to reduce inflammation, and take an antihistamine.
  • Coral – Remove embedded coral by rinsing with seawater or a scrub brush and apply a topical antibiotic.
  • Sea urchin – Remove spines, cleanse the wound, soak in hot water, and apply a topical antibiotic.
  • Anemones – Remove tentacles, rinse with seawater, use ice to relieve pain, apply hydrocortisone, and take an antihistamine.
  • Jellyfish – Remove any tentacles, rinse with seawater, and scrape skin with a credit card, tweezers, or razor to remove nematocysts. Follow this by rinsing with vinegar or rubbing alcohol. Apply hydrocortisone and take an antihistamine. Before you go in the water, find out if box jellyfish are present in the area and if antivenom is available. Note that stings from the jellyfish in the Pacific are serious and can be fatal.
  • Seabather’s erruption – Skin irritation caused by jellyfish and anemone larvae, usually underneath a person’s swimwear. Rinse with vinegar, apply a hydrocortisone to the affected area, and take an antihistamine if itchiness does not stop. Machine wash the swimwear.

What NOT to do if you are stung by a jellyfish

You may have been told to urinate on jellyfish stings. Do not follow this advice. Urinating, rubbing the wound with sand, or rinsing with fresh water activates the nematocysts stuck in the skin. Always rinse with seawater or salt water followed by vinegar. (The only exception to the vinegar rinse is a sting from the Portuguese Man-O-War jellyfish. Vinegar causes it to further activate nematocysts).

Treatment for injected toxins

If venom is injected into your body by a stingray or scorpionfish, seek medical attention immediately for proper wound management, which includes soaking the affected area in hot water for 30-90 minutes. Find out if scorpionfish antivenom is available. For cone snail envenomation, immobilize the limb and apply pressure with a clean dressing. Seek medical attention for proper wound care and pain support.

Dealing with predator bites

The majority of predator bites are the result of being provoked. These types of injuries are common among fishers. If you get bitten by Great Barracuda, moray eels, sea snakes, or sharks like the Great White, Tiger, or Hammerhead, seek medical attention immediately. Note that despite media reports on shark attacks, there are approximately 50 incidents involving humans per year and about 10% of those are fatal.

More information on marine injuries

FAQ Marine Life Injuries – Divers Alert Network (DAN)

Poisoning, Envenomation, and Trauma from Marine Creatures – American Family Physician

By Tullia Marcolongo and Daphne Hendsbee. The authors used information from the presentation “Update on Marine Medicine” (3/28/2014) by Dr. David Boulware, Associate Professor of Medicine, Division of Infectious Diseases and International Medicine, University of Minnesota.

Photo by Wopke (Pexels).