Cnidaria (Jellyfish and Portuguese Men-of-War)
Within the Cnidaria are free-living forms (the medusae or jellyfish) and fixed forms (polyps). Four classes are important for human medicine: Anthozoa (corals and anemones) (Fig. 36-25), Hydrozoa, Scyphozoa, and Cubozoa (cubomedusae) (Figs. 36-26 and 36-27).
Cnidocytes are defense cells that contain organelles called nematocysts, which are triggered and inoculate venom after changes in pressure and / or osmosis) (Figs. 36-28 and 36-29). Many nematocysts initially remain intact in the victim’s skin, without discharging their contents (Fig. 36-30).8
The venom causes intense pain, burning sensation (but it is an envenomation, not a burn), and a linear and urticariform rash with crossed lines (Fig. 36-31). Within hours, the site may exhibit vesicles, blisters, and superficial necrosis (Figs. 36-32 and 36-33). The pain subsists for hours and systemic phenomena can arise, such as cardiac arrhythmias, heart and respiratory failure, and shock, which are responsible for cardiopulmonary deaths in severe cases.9,10 The cubomedusae (Chironex fleckeri, Carukia barnesi, Chiropsalmus quadrumanus, C. quadrigatus, Tamoya haplonema and others) and Portuguese men-of-war (physalia physalis and P. utriculus) can cause accidents of this intensity.11–15 There are hundreds of documented deaths caused by contact with cubomedusae worldwide, most of them are caused by the species C. fleckeri, in the Indo-Pacific region.10 There are also reports of deaths related to accidents with Portuguese men-of-war (P. physalis)16 and the cubomedusa C. quadrumanus in the Atlantic Ocean.2
Immediate allergic reactions also can occur, such as angioedema and anaphylaxis shock. Possible late allergic reactions are persistent lesions after 48 hours, new lesions at distance, or late onset of new lesions.17,18
The larvae of the jellyfish Linuche unguiculata, a small scyphomedusa, are involved in the genesis of seabather’s eruption, a pruritic erythematous papular eruption that develops in areas covered with swimsuits.19,20
Envenomation by anemones can be severe, although usually it causes only mild manifestations (Fig. 36-34). Erythematous, irregular, and painful plaques and papules arise at points of contact with the short tentacles of anemones. The fire corals (Millepora spp.) are in fact hydrozoans that cause severe and extensive envenoming and may lead to medical emergencies. True corals can cause deep wounds in bathers.
The most common complication of accidents from cnidarians is the residual hyperpigmentation, but keloids and atrophy of subcutaneous tissue may arise.1–5 Cuts by corals can develop a foreign body granulomatous reaction.
There is controversy about the treatment of envenomation by cnidarians: in all accidents compresses of iced sea water or cold packs should be used. This measure has a potent analgesic effect and should always be applied even on the beach, as a routine first aid.1–5,12,15 The application of fresh water to the skin triggers loaded nematocysts by osmosis. However, there is a randomized trial that shows the immersion of the affected area in hot water (about 45°C) for 20 minutes to be more effective than ice-cold-water immersion.21 Our interpretation of this finding is that either extreme of temperature interferes with the nociceptive activity of the venom, since cold water also has good analgesic effect, as reported by by earlier studies.1–5,12,15
When the animal involved is a cubomedusa (C. fleckeri, C. barnesi, T. haplonema, or C. quadrumanus) the recommended treatment is the application of 7% acetic acid (vinegar) to inactivate nematocysts still intact on the skin. Although an in vitro experiment showed that the nematocysts of Portuguese men-of-war fired when placed in solutions of vinegar or alcohol,21 in our clinical experience the application of vinegar proved to be a beneficial measure for any accident caused by cnidarians.1–5,12,15
Other measures do not have scientific support and should not be applied. Patients with systemic manifestations (arterial hypotension / hypertension, cardiac arrhythmias, pulmonary edema) should be referred urgently to a hospital. Cardiac arrhythmias should be treated with intravenous use of verapamil.
The deadly tentacles of the Portuguese man o' war | Blue Planet II – BBC One
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Over half of all animals in the open ocean drift in currents. Jellyfish cross entire oceans feeding on whatever happens to tangle with their tentacles. The jellylike Portuguese manofwar can harness sail power to fish with its deadly tentacles.
The big blue is the world’s greatest wilderness, far from shore and many kilometres deep. It’s a vast marine desert where there is little to eat and nowhere to hide. Yet it’s home to some of the biggest and most spectacular creatures on earth.
This episode reveals what it takes to survive in this savage and forbidding world. We witness feats of incredible endurance, moments of high drama and extraordinary acts of heartwrenching selfsacrifice.
Blue Planet II | Series 1 Episode 4 | BBC One
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