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Marine Envenomation (the process by which venom is injected by Venomous Marine animals)
The seas contain many poisonous creatures. While most cause only minor problems, a few are dangerous and may even cause fatal envenomation. Whether you swim, snorkel, dive, fish, or just walk the beach, you should be aware of the risks and how to avoid potential envenomations. In addition, you should know some simple first aid measures in the event of marine envenomation
Types of Envenomation
Sea bathers eruption - Sometimes called "swimmer's itch," sea bather's eruption is caused by microscopic organisms that bloom at certain times in the sea. These organisms tend to get trapped in swim costumes where they prickle or sting and later can cause skin rash where they have been trapped.
Jellyfish - There are 3 important groups of jellyfish: the true (or bell) jellyfish, box jellyfish, and hydrozoan jellyfish. The bell jellyfish have tentacles arranged regularly around the bell; the Chinese sand jellyfish is included in this group. Box jellyfish are box shaped with tentacles arising from their 4 corners; included in this group are the Australian Caruki barnesi or Irukandji (about 2 cm across) and Chironex fleckeri (about 25 cm across with 3m tentacles), the most dangerous of all. Other dangerous species of box jellyfish occur around the Malaysian archipelago and the coasts of South East Asia, and especially the Philippines. Both these groups of jellyfish propel themselves under water as well as drifting with tides and currents.
Hydrozoan jellyfish are made up of a gas filled float that acts as a wind sail with numerous long, tentacles hanging down from this structure. Included in this group is the Atlantic Physalia physalis or Portuguese man-of-war (a blue float 25 cm long, with tentacles up to 30m long). Hydrozoan jellyfish float or roll on the surface of the sea.
Jellyfish tentacles are armed with millions of nematocysts (hollow tubes) that inject a toxin when triggered by contact. In heavy doses the venom of the jellyfish named above may be fatal. Others may cause only local inflammation.
Fish with poisonous spines
Spines on the fins, tail, and gill covers of many species of fish contain complex venoms that cause severe pain, local inflammation, and occasionally systemic symptoms. Rarely, they can cause death. Weever fish that inhabit the Mediterranean and eastern Atlantic cause hundred of stings each year. Dogfish, catfish, lionfish, and scorpion fish have a wide distribution. Most dangerous is the stonefish, whose sting may be fatal. It is found in the Indian Ocean and western Pacific Ocean as far south as Australia. Many species of domestic aquarium fish also have poisonous spines. The spines penetrate the skin and may break off in the skin.
These fish also include fresh and seawater sting rays and manta rays. Stingrays lash their tails and can lacerate the skin or may even penetrate the throat.
Spiny creatures
This group includes sea urchins, starfish, and sea cucumbers, all of which crawl slowly on the seabed. The spines may contain a toxin or there can a separate venom apparatus. Most of the toxins cause pain and inflammation, but the sea cucumber exudes a liquid from its skin that can cause severe inflammation of the eye (conjunctivitis).
Coral
Coral is made up of tiny organisms that lay down a limestone skeleton. Coral reefs harbour myriads of animals, plants, and microorganisms. True corals rarely sting, but the colonizing fire coral can cause dermatitis. Coral cuts can lead to secondary bacterial infection.
Sponges
Sponges are animals fixed to the seabed. Some of them are capable of causing dermatitis due to toxin or allergy. The common species include the fire sponge of Florida and the Caribbean; the poison bun sponge; and the red sponge, which also causes swelling and local muscle stiffness. Sponges may also become colonized by sea anemones.
Mollusks
The 2 dangerous mollusks are the blue ringed octopus and the cone shell of Australia, the western Pacific, and South East Asia. These creatures bite, but the systemic effects of envenomation are more marked than the local ones.
Sea snakes
Distinguished from eels by a flat tail and absence of gills, sea snakes have short, fixed front fangs. The majority of bites are dry, but severe envenomation may be fatal.
Risk Factors
Marine envenomation is a common occurrence among seaside vacationers, snorkellers, swimmers, and scuba divers. Risk depends upon season, wind, current, water temperature, the prevalence of the animal in the area and its precise location, the nature of the swimmers activity, and the use of protective clothing. Tropical seas, especially the western Pacific Ocean, are more dangerous than temperate seas.
Organisms responsible for sea-bathers eruption will be concentrated by on-shore winds in hot weather. Sea snakes cause hundreds of deaths annually among local fishermen who catch them in their nets. Jellyfish stinging is commonest in the warmer oceans and warmest months, and the season is longest nearest the equator. Box jellyfish inhabit shallow coastal waters. Most Chironex stings occur in children and women wading in shallow water. About 200 deaths have been recorded, especially from the Philippines and Australia.
Sea anemones may live on the seabed or among corals, seaweed, or sponges; therefore many types of activity can lead to envenomation. Octopus and cone shells inhabit rocky shores, and fishermen and shell collectors are at risk. About 15 cone shell deaths have been recorded. Spiny creatures live on the seabed and rocky foreshore. Spiny fish are commonly found hiding in coral reefs, where inquisitive snorkellers are at risk. Stonefish lie hidden between rocks or corals; covered in sand, they are difficult to see and bathers easily tread on them. Some species of sting ray hide in the sand, and with a lash of its tail can sting the unwary swimmer in the foot. There are about 1,500 stings from rays and 300 from scorpion fish around the USA each year.
Symptoms
Generalized dermatitis
An itchy rash over areas of the body covered by swim clothes is typical of sea bathers eruption. The rash may be red, often with swelling, but it seldom lasts for more than a few hours. There are rarely any systemic symptoms.
Local reactions to stings and bites
These are painful and there is usually an obvious lesion at the site(s) where toxin has been injected. Local inflammation may develop and is often severe. With some envenomations, systemic symptoms may develop; occasionally these symptoms can be rapidly fatal. Stings from spiny creatures and from coral may leave bits of spine or limestone in the skin and cause chronic local inflammation and bacteria that may cause secondary infection and cellulitis. Sharks and salt-water crocodiles may tear off flesh or limbs.
Systemic symptoms
Systemic symptoms include anxiety, sweating, nausea, vomiting, muscular pain and tenderness, respiratory or cardiac collapse, and neurological symptoms including muscular and respiratory paralysis and convulsions.
Prevention Strategies
You should know the risks of the place to which you are going. Note season, wind, and current, and watch for evidence of algal colonies long the coast. Look for signs warning bathers against entering the water, especially on Australian beaches from October to February. Children are most at risk.
Look out for jellyfish in the area where you are swimming. Some are very small; others have very long tentacles. Jellyfish do not attack swimmers, but swimmers can come into contact with the tentacles. Avoid duck diving when jellyfish are present. Protective clothing, especially "lycra" suits will reduce the risk of jellyfish stings.
Swim from patrolled beaches, and watch for signs warning about sharks and saltwater crocodiles. Wear thick-soled shoes when splashing about on the shore or when in boats, and do not search among rocks with bare hands. Look carefully before putting feet or hands down on rocks while swimming. Never attempt to handle a sting ray, especially one that has been landed into a boat. Some beaches have signs warning of the possible presence of sting rays
Need for Medical Assistance
First aid measures
Swimmer's itch: For itchiness from seabather's eruption, use a simple anti-itch lotion or hydrocortisone 1% ointment. See a physician if there are particles from spines or coral that will need to be removed or if a secondary infection develops that could be treated with an antibiotic.
Jellyfish stings: The sting of the box jellyfish (Chironex), found only in Australia, is a medical emergency and help should be summoned immediately. All lifeguard trucks and stands in Australia stock the anti-venom because the victim can die before reaching a hospital. First aid measures can be undertaken once medical help has been summoned.
First aid measures include the following: Douse the skin with vinegar for at least 30 seconds (for box jellyfish and Portuguese man-of-war) or a thick suspension of baking powder (for the other common Atlantic jellyfish). This will inactivate venom but will not relieve pain. Do not apply alcohol, sun cream, water, or other remedies. Remove any remaining tentacles with your fingers and apply ice packs. A temporary compression bandage (firm but comfortable) over the stung part of the body may help immobilize the limb and minimize the spread of the venom. Seek medical care for the victim.
Stonefish and other severe fish spine envenomations: Immerse the stung limb in water that is uncomfortably hot but not hotter than 113oF (45oC). The hot water will inactivate the venom. Seek medical care for the victim.
Sea snake bite: The victim should lie down and not walk. Immobilize the bitten limb and apply a firm but comfortable compression bandage. Get the victim to the hospital on a stretcher.
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