Before you read the information below please read this:

Every year for a few weeks (no specific month) jellyfish accumulate, in the biobay, that sting. There is always the very occasional sting; but, there are sometimes periods lasting a few weeks wherein a lot of people get stung. Approximately 100 people swim in the biobay each night and your tour operator should inform you if it is a period when there are a lot of stinging jellyfish. If you are swimming with young children be sure to ask about recent occurrences. Most of the stings are mild, it can really hurt for awhile, but the pain is usually over with rather quickly, should you get a more severe sting it may last to the next day.

NOT RUBBING is the best treatment. Applying some vinegar to stop the nematocysts from firing new stingers would be the second treatment. Then remove any 'gossamer' strings you can find. ( the skin on your fingers usually cannot feel the stinging so removal with your fingers is ok). After this, the best thing is very hot water ( but not burning) and that is about all you can do but wait for the pain to go away. Some people use amonia. I suggest you do NOT use meat tenderizer.

------------- The following information is from John Hopkins University ------

With more than 10,000 species in the sea, jellyfish are responsible for the most common human envenomations. More than 100 species are toxic to humans, and contact with toxic jellyfish causes a wide range of conditions, from cutaneous rashes to cardiovascular and respiratory collapse.

Jellyfish are categorized into 4 classes as follows:

• Hydrozoa (Portuguese man-of-war)
• Scyphozoa (true jellyfish; most common)
• Cubozoa (box jellyfish; most toxic. NOT found in Caribbean)
• Anthozoa (sea anemones and corals)

Jellyfish have a single gastrovascular cavity opening, which is used for digestion and circulation, and a set of tentacles. The tentacles are covered with batteries of specialized stinging cells termed nematocytes. Each nematocyte contains a stinging apparatus known as the nematocyst. This stinging apparatus basically consists of a poison sac with an attached sharp hollow tube armed with barbs.
Detached tentacles found on the beach pose a hazard to humans because they remain capable of envenomation for several weeks.

Pathophysiology: The stinging process of the nematocyte resembles a jack-in-the-box mechanism. Specifically, mechanical and chemical stimulation of the sensory hairs (ie, cnidocil) surrounding the pressurized nematocyte results in a calcium-mediated bioelectric signal that causes an opening of its lid, allowing the ejection of the nematocyst into the prey to express the venom. This pressurized process has a high internal hydrostatic pressure of 150 atm that causes the ejection to occur within 3 milliseconds, with an acceleration power of 40,000 G and a force of penetration of 20-33 kilopascals. In addition, the nematocyst is capable of penetrating up to a depth of 0.9 mm. This depth deposits the toxin into the microvasculature of the dermal tissue to be absorbed into the systemic circulation and anchors the tentacles to the prey. Finally, the nematocyte must be replaced because it cannot regenerate the ejected nematocyst. This replacement is done via differentiation of the pluripotent cells.

Nematocysts

The nematocysts' size and arrangement on jellyfish tentacles differ from species to species, much like a fingerprint. This architectural arrangement of warts, ridges, spirals, and terminal swelling may be reflected in the skin pattern left via the sting and helps identify the species involved in the envenomation.

Toxin

Microscopically, nematocysts appear structurally similar from one species to another, but the venom differs in composition. For example, because the box jellyfish feeds on fish larger than its own body, it requires potent venom for rapid paralysis. While the amount of toxin expressed by a single nematocyst is minute, several thousand nematocysts discharging at once have a significant effect.
Functionally, the toxin causes sodium and calcium ion transport abnormalities, disrupts cellular membranes, releases inflammatory mediators, and acts as a direct toxin on the myocardium, nervous tissue, hepatic tissue, and kidneys.
Specifically, the toxin may contain catecholamines, vasoactive amines (eg, histamine, serotonin), kinins, collagenases, hyaluronidases, proteases, phospholipases, fibrinolysins, dermatoneurotoxins, cardiotoxins, neurotoxins, nephrotoxins, myotoxins, and antigenic proteins. The protein component of the toxin tends to be heat labile, nondialyzable, and is degradable by proteolytic agents.

Reaction to venom

Immediate acute reactions to the venom tend to be toxic rather than allergic. Since pain occurs immediately after exposure, venom injection into different mammals induces similar clinical results, and victims can be stung repeatedly without differences in symptoms. The more rapidly the venom gets into the bloodstream, the higher the venom concentration in blood and the more rapid the onset of systemic symptoms. Delayed reactions to jellyfish stings are related immunologically, as evidenced by persistent immunoglobulin G (IgG) levels, prolonged T-cell response, and cross-reactivity among various jellyfish venom antigens.

Frequency:

• Internationally: Jellyfish stings occur in tropical oceans, especially between latitudes 30° south to 45° north, because of a high natural concentration of coelenterates.

Mortality/Morbidity:

Jellyfish stings usually are mild, except those caused by species in the South Pacific, such as the box jellyfish or Portuguese man-of-war. Exact mortality and morbidity is not known because of underreporting and the lack of an international jellyfish sting registry.

• The sting of the Portuguese man-of-war is more painful than a common jellyfish sting. It has been described as feeling like being struck by a lightning bolt, and some victims dread it more than a shark bite. This sting has been responsible for 2 reported deaths.

In Vieques we occasionally get Portuguese man-o-war jellyfish, every few years.

Race: No racial predilection exists. Any differences in individual reactions to jellyfish are a reflection of immune status rather than race.

Sex:

• Lower body weight makes women more susceptible than men to the same amount of jellyfish venom.

Age:

• Children are most susceptible to the effects of toxins because of their large surface area–to–volume ratio and lower body weight.
• Older adults are more susceptible than younger adults because of their decreased physiologic reserves and concurrent debilitation.

CLINICAL

For patients presenting with jellyfish stings, it is essential to ascertain (1) the time of envenomation, (2) the nature of the incident, (3) a description of the coelenterate, and (4) local and systemic symptoms.

• Toxicity and variations of symptoms depend on several factors.
Patient age and health, Patient body weight relative to the toxin amount, Patient surface area involved in the sting (any sting >50% of limb area is associated with severe envenomation), Thickness of the skin at contact points (calloused palms and soles are most resistant), Site of envenomation (proximity to head and torso results in quicker venom absorption into central circulation)

Species of the jellyfish
Maturity of the jellyfish
Venom potency
Number of nematocysts discharged

• Hot water sensation with skin tingling or stinging may be reported at the body site where the jellyfish originally made contact, secondary to pain and stinging after the release of thousands of nematocysts at the site.

• Variations in reactions to the sting appear to be related to the specific toxicity of the venom. Venom deposited intravascularly causes quicker onset of symptoms and signs. Physical findings of envenomation can be classified as local effects, systemic effects, delayed effects, or specific jellyfish syndromes.

• Mild envenomation
Local skin contact reactions
Tenderness, burning, and pruritus, which may spread centrally and differ in intensity depending on the species involved
Local soft tissue edema and angioedema
Erythematous papules and blisters in a whiplike pattern with desquamation within 1-8 weeks
Ischemic changes distal from localized arterial vasospasm underlying the sting site
Thrombophlebitis of the vessel underlying the sting site
Local neuropraxia occurring adjacent to sting site from immunologic reaction to toxin or to toxin-induced alteration of the nerve's ionic permeability
Tender regional lymphadenopathy
Distant skin site reactions secondary to a hypersensitive response to the antigenic component of the venom

• Moderate or severe envenomation implies the appearance of systemic symptoms following the initial localized reaction.
Cardiovascular
Peripheral and coronary vasospasm
Dilated cardiomyopathy
Hypokinetic cardiac failure (hyperkinetic failure in Irukandji syndrome)
Arrhythmia from toxin-induced damage to Purkinje fibers
Cardiovascular collapse or arrest, usually indicating a larger amount of envenomation than in respiratory arrest
Respiratory, Laryngeal edema, Bronchospasm, Pulmonary edema/acute respiratory distress syndrome, Hypoxia and acidosis from intercostal muscle spasm and pain, Respiratory failure and arrest, Neurologic, Autonomic dysfunction from alteration of sodium and calcium ion transport, Spastic paralysis, Headache, agitation, and neuropsychiatric disturbances, Ataxia, Cerebral edema, Seizures, Stupor or coma, Gastrointestinal, Nausea and vomiting, Abdominal muscle rigidity and pain, Hypersalivation and dysphagiak, Hepatic inflammatory necrosis from direct toxin injury to hepatocytes, Renal failure from toxin-induced glomerulonephritis or RBC hemolysis, Musculoskeletal, Incapacitating muscle spasm of limb and torso, Reactive arthritis, Rhabdomyolysis, Hematologic/immunologic, Hemolysis, Hypersensitive reaction (anaphylaxis is rare), Long-term or delayed reactions, Keloids, Pigmented striae, Lichenification from persistent rubbing, Granuloma, Ulceration and necrosis, Gangrene, Fat atrophy, Scarring and contractures, Recurrent reactions without repeated exposure occurring at the original sting site secondary to sequestered, intracutaneous, antigen-induced, immunologic reaction (may be more severe than original reaction)

Irukandji syndrome
Delayed, severe, systemic symptoms occur 10-40 minutes (mean of 30 min) after the initial sting by Carukia barnesi. The latent period results from traveling of the venom in the lymphatic system into the central circulatory system.
The sting frequently is not visible or may resemble small insect bites.
Systemic symptoms may mimic an autonomic-excess picture with abdominal muscle rigidity, vomiting, profuse sweating, and excessive shaking followed by pyrexia, tachyarrhythmias, hypertensive crisis, and hyperkinetic cardiogenic shock with pulmonary edema.
Box jellyfish envenomation ( NOT in Caribbean)
Pathognomonic frosted-looking lesions develop in a transverse crosshatched pattern 8-10 mm wide. Secondary blistering occurs.
Lesions occur within 6 hours of the sting and superficial ulceration or necrosis follows in another 12-18 hours.
Immediate, intense, localized pain occurs with incapacitating muscular spasm resulting in death by drowning.
The pain and spasms spread centrally as the venom travels to the central circulatory system, inducing parasympathetic overstimulation and respiratory-cardiac arrest.
Causes:
• Injury occurs as a result of accidental exposure to jellyfish tentacles. Jellyfish move slowly and are nonaggressive.
• Bathers, waders, and divers are at risk of contacting these creatures in seawater with strong currents or poor visibility.
• The curious are at risk because of careless or unknowledgeable handling of jellyfish.