עקיצת מדוזה

What are jellyfish?

Jellyfish are soft-bodied free-swimming animals with a jelly-like umbrella-shaped bell and trailing tentacles. The tentacles are covered in tiny sacs (called nematocysts) which release venom.

חלקם חיים במים מתוקים, חלקם במים רדודים ליד החוף, וחלקם באוקיינוסים העמוקים. מאמינים שהם המין החי הוותיק ביותר עם מספר איברים, והם קיימים כבר למעלה מ-500 מיליון שנה.

איך מרגיש עקיצה של מדוזה?

Symptoms of a jellyfish sting include:

• Localised stinging pain,

• Itching,

• Rash,

• פסים מוגבהים (בליטות).

For the vast majority of people stung in UK waters this will be the experience of a jellyfish sting. The initial intensity varies from something like a nettle sting to something like a sudden burn to the skin, although man-o'-war stings can then become more sore before the pain settles down.

Some less common symptoms include:

• Being sick (vomit).

• שלשול.

• כאב בטן (בטני).

• Numbness/tingling in limbs.

• Muscle spasms.

בבריטניה זה סביר יותר אם יש לך מספר עקיצות ממדוזת רעמת האריה, מדוזת מצפן, מדוזת עוקץ סגול או ממדוזת פורטוגזית.

Allergic reactions to jellyfish stings are unusual but may cause swelling, chest tightness, trouble breathing and anaphylaxis. Anaphylaxis is a medical emergency - see the separate leaflet called Anaphylaxis.

Do all jellyfish sting?

Not all jellyfish sting. Of those that do sting, very few are dangerous to human beings. There are more than two thousand known species of jellyfish, but it is estimated that three hundred thousand are yet to be discovered.

Most jellyfish stings result from swimming into jellyfish, wading into them in shallow water, walking on them (or parts of them) when they are washed up on the beach, or attempting to handle them.

Swimmers are at the greatest risk; most ocean distance and endurance swimmers regularly experience repeated jellyfish stings.

Are jellyfish poisonous?

This depends on what you mean by the term poisonous. Most UK jellyfish can sting, although none is dangerous to life. Some have very painful stings - but the term 'poisonous' is usually reserved for toxins which can cause real and lasting harm.

Box jellyfish are a large group of jellyfish species. The most dangerous varieties are found in the Indo-Pacific, and these have venom which is definitely poisonous. They are very different to the jellyfish found in UK waters, as they are able to see, and to propel themselves, and they can sting when in close proximity even without being touched. Some of these jellyfish have extremely venomous stings which can be a danger to life.

There is also a large group of jellyfish called sea nettles that are mainly found in the Pacific and the Atlantic oceans. They are not usually lethal to humans but an allergy to the sting may cause serious problems.

אילו סוגי מדוזות נמצאים בבריטניה?

The UK has six species of true jellyfish and two species of jellyfish-like animals, the Portuguese man o' war and the by-the-wind sailor.

Common jellyfish

מדוזות נפוצות נמצאות בכל המים של בריטניה, במיוחד בשפכים ובמפרצים, ונראות בעיקר מאמצע האביב ועד אמצע הקיץ. הן שקופות, עם זרועות ציד בצבע ורוד חיוור או כתום, וקוטר של עד 30-40 ס"מ. העקיצה שלהן קלה מאוד.

Compass jellyfish (or dial jellyfish)

אלה שקופים עם פסים כתומים-חומים המקרינים מהמרכז, כמו נקודות של מצפן. עד 30 ס"מ לרוחב, יש להם 24 זרועות דקות וארוכות וארבע 'זרועות' מתנפנפות עם קצוות. הם נמצאים בעיקר בחצי הדרומי של בריטניה בקיץ. למרות שהם לא מסוכנים, העקיצה שלהם יכולה להיות די כואבת, כמו עקיצה של סרפד רע.

Blue jellyfish

These are bright blue/purple with a frilly edge and long, fine tentacles. They are common in the South West and Wales in spring and summer, and have a mild sting.

Lion's mane jellyfish

These much larger jellyfish prefer colder waters, and are found mainly from North Wales to the north of Scotland (and further north). The frilled bell is reddish-brown and can be up to two metres in diameter.

The multiple very fine tentacles trail for 10-20 metres and have a painful sting. Bits of tentacles can break off the animal and drift in the tide, where they may still sting. The sting is sometimes describes as feeling like an electric shock.

מדוזת חבית

These pale creamy-pinkish barrel jellyfish have a solid, rubbery bell up to one metre in diameter, with purplish markings around the edge. They are found mainly on the Western side of the British Isles in summer and autumn. They do not have tentacles but eight thick, frilled cauliflower-ish arms, and have only a very mild sting.

מדוזת צריבה סגולה

These small (10 cm) Mediterranean jellyfish are covered in pink or mauve warts, and have four long frilled arms. They are rare in the UK, but common in the Mediterranean in summer. They have a painful sting, sometimes described as like an electric shock or sometimes like a nettle sting.

מדוזת סירה פורטוגזית

The Portuguese man o' war, Physalia physalis, is not a jellyfish but a group of many different individual animals called zooids, attached and co-dependent, so that they behave as one animal.

Found in the Atlantic, Indian and Pacific Oceans, these creatures travel in large groups, sometimes of hundreds of thousands, so where one man o' war is beached others often follow.

In the last few years there have been several reports of groups of the creatures drifting off British shores and blowing up on to beaches. Like most jellyfish they float on the sea's surface and drift with the wind and currents - they can't propel themselves.

The man o' war is translucent with a purplish tinge, and the 'body' can be up to 30cm long, but the tentacles are typically ten metres long and can reach thirty metres or more. The visible part is a gas-filled bladder which is visible above the water and acts as a sail.

לזרועות יש נמטוציסטים מלאי ארס אשר עוקצים, משתקים והורגים דגים קטנים במגע. אלה גורמים לעקיצה כואבת מאוד בבני אדם, שמתוארת לפעמים כהרגשה של כוויה פתאומית עם שוט חם.

זרועות של חלקי זרועות לעיתים קרובות נשברות ויכולות להיסחף במשך ימים, עדיין ארסיות, עם פוטנציאל לעקוץ שחיינים. לאחר שהן נשטפות לחוף ונראות כאילו אינן פעילות, המדוזה עדיין עוקצת, מכיוון שהציסטות על ה'זרועות' יישארו חיות לזמן מה.

מוות ממדוזת הפורטוגזית אפשרי אך נדיר ביותר - דווחו שני מקרים בחמישים השנים האחרונות, ואף אחד מהם לא במים של בריטניה. בשני המקרים נראה שהקורבן סבל מתגובה אלרגית (אנפילקסיס) to the sting.

שייט עם הרוח

The by-the-wind sailor, velella velella, is a group of organisms like the Portuguese man o' war. It is blue with a distinctive triangular sail on top of a circular base under which hang small tentacles. It can occur in vast swarms and huge numbers are occasionally stranded along the South West and Welsh coastlines. Unlike the man o' war, it is harmless.

איך לטפל בעקיצת מדוזה

It is useful to know what to do if you get stung by a jellyfish in the UK, although if you swim in tropical seas, particularly the Indo-Pacific, it is vital to have this information and to be prepared.

בהקדם האפשרי, הסר כל זרועות נותרות, מבלי לגעת בהן עם עור חשוף. השתמש במקל. אם אתה משתמש בפריטי לבוש או מגבות, אל תלבש או תשתמש בהם לאחר מכן.

• Rinse thoroughly in seawater to wash off all the cysts you can. Do not use fresh water, as this may make any jellyfish parts remaining leak further venom.

• After rinsing thoroughly, soak or rinse the area in vinegar (acetic acid) for about 30 seconds. This will prevent the cysts from releasing their toxins by disabling them.

• אם אין לך חומץ זמין, המשך לשטוף במי ים, או בג'ל מסחרי להקלה על כאבי מדוזות.

• Do not rub the area yet as there may be cysts clinging to your fine body hairs and you will break them and potentially will sting your hands.

• Do not yet apply ice or hot water.

• Apply shaving cream to the area. Shave the area with a razor or credit card to remove any adherent cysts. Then reapply vinegar or alcohol. The shaving cream prevents cysts that have not been activated from releasing their toxin during shaving.

• Eye stings should be rinsed with a commercial saline solution like Artificial Tears®; dab the skin around the eyes, using a towel that has been soaked in vinegar. Do not place vinegar directly in the eyes. If you are on the beach, use sea water.

• Mouth stings should be treated with ¼-strength vinegar. Mix 1 to 3 parts vinegar to water. Gargle and spit out the solution.

• If the person who has been stung starts to feel general symptoms which are not local to the sting, such as feeling sick, being sick (vomiting) or tummy (abdominal) pain, seek medical advice urgently.

איך אני יכול להימנע מעקיצות מדוזות?

Avoid touching jellyfish. It is generally better not to touch a jellyfish at all, even if you think it is a harmless variety and even if it is beached and appears dead, as it may still sting.

If you see jellyfish in the water, swim away and be aware that jellyfish are generally found in groups.

A wetsuit will protect you against most jellyfish stings, although exposed parts of your skin like hands, face and feet will still be stingable.

איך מרגיש עקיצה של מדוזת פורטוגזית?

The sting of the man o' war is very painful, and is often described as feeling like a sudden burn on the skin. There are around 10,000 human stings caused by the man o' war in Australia each summer, mostly on the east coast.

Stings are normally multiple, causing skin wheals longer than 20 cm. Some severe skin injuries turn into scabs lasting for about two weeks before resolving and leaving red scars. Stings cause pain lasting 2-3 hours. Wheals are usually extremely sore, and leave red open welts on the skin that last 2-3 days.

במקרים פחות שכיחים, הארס יכול לגרום לתגובה דומה לאלרגיה, כולל נפיחות בדרכי הנשימה, הפרעות בקצב הלב וקושי בנשימה. תסמינים נוספים יכולים לכלול חום גבוה (חום) ושוק. עקיצות קטלניות הן נדירות מאוד, ובדרך כלל נובעות מתגובה אלרגית לעקיצות מרובות.

How do I treat a sting from a Portuguese man o' war?

Treatment is on the same principles as other stings. It aims first at removing remaining cysts from the skin, where they may be trapped by body hairs. Start by pouring lots of salt water on to the skin. Avoid fresh water or alcohol, both of which can make cysts burst, releasing more venom.

Rinse thoroughly with vinegar for about 15-30 seconds to deactivate the remaining cysts and help neutralise the venom and the pain.

Rinse for a further 15 minutes. If you can, apply shaving cream to the wound for 30 seconds, then shave the area with a razor (rinsing between each stroke). This is the best way to remove remaining cysts trapped in or clinging to the skin's hairs. If you don't have a razor, use a credit card to scrape the skin, then rinse again and reapply vinegar for another 15-30 seconds.

Only apply heat or cold AFTER this. Hot packs then speed the breakdown of the man-o'-war toxins already in the skin.

In a trial on 96 swimmers accidentally stung by Physalia, hot water immersion at 45°C was better than ice, although ice can be helpful.

Topical vinegar is not universally accepted as treatment for Portuguese man-o'-war stings in Australia, as it can worsen stings from a similar multi-tentacled Physalia מינים החיים במים האוסטרליים. עם זאת, המין הרב-זרועי לא דווח מחוץ לאוסטרליה, וחומץ נשאר הדרך המומלצת לטיפול בעקיצות מדוזות במקומות אחרים.

Where are the most dangerous jellyfish found?

המינים המסוכנים והקטלניים ביותר של מדוזות, בכל הנוגע לבני אדם, הם חלק ממדוזות הקופסה הנמצאות באוקיינוס האינדו-פסיפי ובסביבת חופי אוסטרליה, במיוחד בצפון, ובפיליפינים. מדוזת הקופסה האוסטרלית ידועה גם כצרעת הים.

מדוזות הקופסה הן בצבע כחול חיוור ושקופות עם פעמון דמוי קובייה. לכל אחת יש עד 60 זרועות, הנושאות אלפי תאים צורבים. הירי מופעל לא על ידי מגע אלא על ידי חישת כימיקלים על פני השטח החיצוניים של הטרף.

Box jellies can move purposefully rather than just drift, travelling at up to four knots, and hunting for food. They have clusters of eyes on the four sides of their bell, with pairs of eyes on each side possessing a lens, retina, iris and cornea, although as they have no central nervous system, it is unclear how they process what they see.

There are multiple box jellyfish varieties. Not all are dangerous, but the best known (and most dangerous) are the huge Chironex whose venom affects the heart, and the tiny Irukandji, whose venom can cause Irukandji syndrome, affecting the heart, nervous system, and skin.

איך מרגיש עקיצה של מדוזת קופסה?

Box jellyfish stings are very painful. The box jellyfish fires its venom and cysts into the skin, greatly increasing their harmful potential. One of the reasons for the particular hazardous nature of box jelly stings is that those stung can go into shock, rendering them unable to swim, so that they drown before reaching shore.

Chironex fleckeri is a very large box jellyfish, with a venom that can cause heart rhythm disturbance and cardiac arrest. Stinging from contact with four feet of tentacle can kill an adult man, and two feet can kill a child. Smaller stings are not usually fatal. About 40 people a year die in the Philippines from box jellyfish stings. In Australia, where beaches are netted and public awareness is high, fewer than 100 people are thought to have died from box jellyfish stings since 1883, although some unexplained swimming deaths may relate to the creature.

Chiropsalmus quadrigatus is a slightly smaller, very common and equally dangerous species in the Indo-Pacific Ocean, also found less frequently in Caribbean seas. It is believed to have caused large numbers of fatalities in pacific waters, but not in Australia.

Irukandji jellyfish are small - measuring only 1-3 cm across (depending on the type), but the barely visible tentacles may be a metre long. They inject venom and cysts into the skin, causing Irukandji syndrome. This involves severe muscle pain including severe low back pain, rapid heart rate, massively raised blood pressure, nausea, headaches, sweating, muscle numbness, chest tightness, restlessness, sickness (vomiting) and a terrible sense of doom. In severe cases they have been known to cause brain haemorrhage. There is a delay of around 30 minutes before symptoms begin.

About 100 people are hospitalised each year in Australia due to Irukandji syndrome. A single sting is not usually fatal, although multiple stings from a group of jellies are extremely dangerous. Fatalities are very rare, but hospitalisation with induced coma can be needed for up to two weeks to manage symptoms. Survivors may experience considerable pain for weeks, and are usually left with permanent scarring where the tentacles made contact.

Fear of box jellyfish closes almost all of the beaches of Northern Australia. The few beaches that remain open have jellyfish netting, and lifeguards wear neck-to-ankle Lycra® suits. Signs warn swimmers not to rub a sting, but instead to douse it in vinegar.

איך אני מטפל בעקיצה של מדוזת קופסה?

Most beaches where these jellyfish are found have warning signs for marine stingers, so treat any sudden sting as if it's a box jelly in these circumstances.

• Immediately flood the area with household vinegar to keep un-discharged nematocysts from firing. This does not relieve pain but prevents additional stings.

• Never rub the area with sand.

• Pluck off any vinegar-soaked tentacles with a stick or other tool.

• אם לנפגע יש קוצר נשימה, חולשה, התכווצויות שרירים, תחושת דפיקות לב (פלפיטציות) או כל תסמין כללי אחר, יש לקרוא לעזרה רפואית דחופה.

• For pain relief, apply ice packs. If pain becomes unbearable, seek medical advice. No studies support applying heat to these stings.

• Meat tenderiser, baking soda, papaya, commercial sprays, alcohol, and urine are not effective. They often have harmful effects, causing more damage.

• If a red streak develops between the sting site and neighbouring lymph glands, or if either area becomes red, warm and tender, seek medical help immediately.

• Do not delay in calling for emergency medical help if the victim shows signs of a significant reaction.

• הטיפול הרפואי כולל אנטיהיסטמינים, משככי כאבים חזקים ותרופות להורדת לחץ דם.

• There is some evidence that strong local anaesthetic solutions help the pain of some box jellyfish stings.

האם יש מדוזות קופסה בבריטניה?

Box jellyfish live in warm waters, not the colder waters of the UK. This information on box jellyfish is included because people are interested in them and often want information. If you visit the Pacific or Australia, take note of local advice regarding swimming and do not swim on beaches which are closed due to hazardous marine life.

Very painful jellyfish stings are rare in UK waters, and there are no records of anyone ever being killed by jellyfish in the UK. Fatal jellyfish stings are incredibly unlikely. Be sensible; avoid jellyfish if you see them and consider wearing a wetsuit if you like to spend time in the sea. If you see large numbers of jellyfish drifting together (sometimes called a bloom) then get out of the water, but don't let the idea of jellyfish prevent you from enjoying exercise and the ocean.

Increasing sea temperatures are likely to affect where jellyfish are found. There are reports from Australia of box jellyfish being found further south, round the Australian coast, than in the past, but these particular jellyfish remain in the wrong part of the world's oceans to represent a possible threat in the UK. Whilst there are varieties of box jellyfish in warmer Atlantic waters much nearer to the equator than us, the main risk to swimmers in the UK is not from sea life but from currents and tides.

ד"ר מרי לות' היא מחברת או המחברת המקורית של עלון זה.