Jellyfish

The stinger season runs from October 1 to May 31 when box jellyfish are more likely to be in the water.

The major box jellyfish has quick acting venom in its tentacles that can kill a person in less than five minutes. Box jellyfish are almost invisible in the water, with a bell up to 35cm in diameter and up to 60 tentacles that can reach up to three metres long. 

Millions of stinging cells (nematocysts) cover each tentacle that inject venom into the skin on contact.

What happens if you're stung

If stung, you will feel immediate excruciating pain and within minutes white welts will appear where the tentacle touched the skin.

These welts change to red whip-like lines and subsequent skin death may lead to permanent scarring. A large dose of venom, particularly in small children, can cause rapid cardio respiratory arrest and death within a few minutes.

When and where stings occur in the NT

Although most jellyfish stings have occurred in the stinger season, there have been stings in other months of the year. 

Many stings happen in shallow water less than one metre deep, such as in tidal creeks or around boat ramps.

Stings are less common on outgoing tides and more common on days with still conditions. 

Prevalence of stings in the NT

Top End hospitals and health clinics report around 40 people with jellyfish stings each year in the NT. The last reported death in the NT was in November 2007 when a six-year-old boy from a remote Aboriginal community died from confirmed C. fleckeri envenomation.

Children are more at risk of life-threatening envenomation due to their smaller body mass in relation to the volume of venom injected.

Where jellyfish are found

The jellyfish that cause Irukandji syndrome have been found along Australia’s northern coastline from Fraser Island in Queensland across the NT to Broome in north Western Australia. 

Irukandji syndrome has also been reported in parts of Asia, the Caribbean and Hawaii.

Protection from jellyfish

The best way to avoid jellyfish stings is to not go into sea water, especially during the time when jellyfish are more common. You should remember that stings are possible at any time of the year.

Young children should not enter the water at all during stinger season. If entering the water, children should wear protective clothing, such as stinger suits or long shorts and a long sleeved top. 

Older children and adults should also wear protective clothing if entering the water.

Irukandji syndrome

Stings from several species of smaller jellyfish can cause Irukandji syndrome.

Irukandji syndrome has a diverse range of symptoms that can occur following a sting from one of several types of box jellyfish. 

The syndrome can be mild for some and severe and life-threatening in others. 

Signs and symptoms

If you are stung you may or may not feel a mild pain at the sting site and develop a goosebump-like skin reaction. After about 30 to 45 minutes symptoms worsen to include: 

  • severe limb, abdominal and back pain 
  • anxiety 
  • headache
  • vomiting
  • profuse sweating 
  • sometimes difficulty breathing.

Your heart rate may become very rapid and your blood pressure may become very high. In extreme cases, heart failure, swelling of the brain and death may result.

In some cases the symptoms resolve in a matter of hours, but many patients need to go to hospital to recover from symptoms over several days. Complications from envenomation may continue for several days to weeks.

What type of jellyfish cause Irukandji syndrome

There are about 14 different box jellyfish that can cause Irukandji syndrome. The bell of the box jellyfish is a ‘box shape’ with a single tentacle arising from each of the four corners. The tentacles range in length from a few centimetres to 35cm. 

These box jellyfish are difficult to see in water as they are colourless with a bell of 2.5cm diameter or smaller.

Difference between jellyfish causing Irukandji syndrome and the major box jellyfish Chironex fleckeri

The adult major box jellyfish, Chironex fleckeri, has a larger bell of 25 to 30cm in diameter and has 10 to 12 tentacles at each corner of up to two metres or more in length. 

It is extremely venomous causing immediate severe pain and the appearance of white welts within minutes followed by red whip-like lines that can blister. 

In some cases cardiac arrest and death occurs within five minutes of being stung by a Chironex fleckeri jellyfish.

Time of the year Irukandji syndrome occurs

Irukandji syndrome has been recorded in the Northern Territory (NT) all year round. Stings occur less frequently during the Dry Season. 

Around 40 people present to Top End hospitals or health clinics each year with a condition attributed to a jellyfish sting some of which will be Irukandji syndrome.

Treatment for jellyfish stings

Immediate first aid for a jellyfish sting is important and the victim may need cardiopulmonary resuscitation (CPR).

Treatment for jellyfish stings can include any of the following:

  • remove the person from the water
  • call for help - call 000
  • assess the person and start CPR if needed
  • pour vinegar on the area of the sting to stop further discharge from the stinging cells - do not wash with fresh water
  • if vinegar is not available, pick off any remaining tentacles and rinse sting with salt water - the skin on the finger pads and palm is thicker so any stinging will usually be minor
  • seek medical help and transport to hospital immediately
  • ice can be applied for local pain relief for less severe stings.

Contact

For more information go to the Australian Marine Stinger Advisory Services or Surf Life Saving Northern Territory websites.

Or call your nearest Centre for Disease Control.

Last updated: 27 June 2017