What is Irukandji Syndrome?
Irukandji syndrome is a painful and potentially fatal condition caused by stings from certain types of jellyfish, particularly those from the Cubozoa class, also known as box jellyfish. While the sting itself might seem mild, within about 30 minutes, it can cause a series of severe symptoms similar to a sudden rush of adrenaline. These may include a rapid heartbeat, high blood pressure, intense pain, and muscle cramps. This is frequently followed by low blood pressure, fluid in the lungs, and potentially dangerous heart issues.
The syndrome was named in 1952 by Hugo Flecker after the Irukandji, an Aboriginal tribe near Cairns, North Queensland, Australia. The most common cause of Irukandji syndrome is the Carukia barnesi species of jellyfish. This species was named after scientist Jack Barnes, who proved it caused the syndrome in a rather unconventional way—Irukandji syndrome is most recognizably caused by the Carukia barnesi species of jellyfish. Barnes found out the hard way that this type of jellyfish could cause the syndrome when he, his son, and a local lifeguard were stung and needed hospital treatment. This is why Carukia barnesi is often referred to as the “Irukandji jellyfish.”
What Causes Irukandji Syndrome?
Carukia barnesi is a type of small jellyfish with a diameter of about 2 cm and 4 tentacles. Despite its small size, it can sting through materials made to resist jellyfish stings. While this species is most commonly associated with a condition known as Irukandji syndrome, there are actually up to 25 species that can cause the same condition. Most of these species belong to the same family, Carybdeida, including but not limited to species like Alatina mordens, Malo maxima, Carybdea alata, Carybdea xaymacana, and Carybdea rastonii.
Though Carukia barnesi and similar species belong to the same group as the Chironex fleckeri, commonly referred to as “the box jellyfish” or “the sea wasp,” it’s important not to confuse them. These different jellyfish types can cause very different health problems with significantly different outcomes.
Risk Factors and Frequency for Irukandji Syndrome
Irukandji syndrome, which was initially thought to only affect areas along Australia’s northern coastline, has been reported worldwide, with cases identified in Thailand, the Caribbean, and the American states of Florida and Hawaii. While the specific species causing the syndrome isn’t always identified, it’s known that this syndrome has a global impact.
In Australia, between 50 to 100 hospitalizations per year occur due to stings related to this syndrome. Marine activities such as snorkeling, scuba diving, and swimming have been linked to these stings. The economic cost is significant, not only affecting the health system but also impacting tourism, fishing, and commercial diving. Irukandji stings typically follow a seasonal pattern with two peak periods, but this can vary regionally, due to environmental factors like wind patterns and the lifecycle of the jellyfish, rather than human activity.
- In Northern Australia, the peak periods are May and October.
- In Western Australia, peak stings occur from October to December and March to June.
Despite the regional variations, other environmental factors that have been linked to a higher number of stings include low winds, high temperatures, less rainfall, increased sunlight, and high tides.
Interestingly, stings from these jellyfish often occur in short, large-scale outbreaks, with many people getting stung in a limited time frame at a particular beach. For instance, on Christmas Day in 1985, there were 36 reported stings. The reason for such concentrated outbreaks isn’t clear, but it’s these major events that draw public attention.
Signs and Symptoms of Irukandji Syndrome
The symptoms of a jellyfish sting, or Irukandji syndrome, typically start with a mild stinging sensation at the site of the sting. This stinging, which is often caused by an unnoticed jellyfish, can quickly wax and wane within half an hour. Alongside this initial pain, sufferers can experience noticeable red bumps on the skin that resemble goose pimples. These skin changes, which are usually about 2 cm in diameter (just like the jellyfish that caused them), can disappear shortly or persist for several days.
More serious, body-wide symptoms can emerge anywhere within the first two hours after being stung. The classic Irukandji syndrome includes back pain, muscle cramps all over the body, nausea, vomiting, profuse sweating, and headache. People also often experience feelings of anxiety, agitation, and a sensation of “impending doom.” Furthermore, due to the effects of the jellyfish’s toxin, high blood pressure and fast heartbeat are common. It’s worth noting that in extreme instances, victims have reported blood pressure readings as high as 300/180 mm Hg.
Although the symptoms generally improve within 24 hours, they can return. In severe cases, the heart can fail, leading to fluid buildup in the lungs and breathing difficulties. There have been reports of death caused by brain bleeding, a complication of very high blood pressure.
Curiously, most reported cases of Irukandji syndrome occur within enclosed nets designed to prevent jellyfish stings. This likely happens because the responsible jellyfish can fit through the 2 cm openings in these enclosures. Tourists, especially those not aware of these small jellyfish, are particularly at risk. Therefore, a history of tourism or foreign travel could suggest a possible diagnosis of this syndrome. Finally, it’s worth noting that jellyfish stings often occur in bursts, so it’s not unusual to see many patients with similar symptoms arriving in the hospital emergency department on the same day.
Testing for Irukandji Syndrome
When dealing with a condition like Irukandji syndrome, caused by the sting of a specific type of jellyfish, your doctor will need to know all about your medical history and do a thorough physical examination. This is vital to make an accurate diagnosis and differentiate it from other conditions that might display similar signs. It’s worth noting that no widely available laboratory test can confirm the presence of Irukandji syndrome. Therefore, the diagnosis is usually made based on your symptoms and medical history.
Even though the diagnosis relies heavily on symptoms, your doctor may still perform some tests. However, the primary aim of these tests is to rule out other causes of your symptoms and identify any complications related to Irukandji syndrome. Before performing any tests, your doctor will ensure your airway, breathing, and circulation are stable.
One of the tests might be an Electrocardiogram (ECG), a simple test that records the heart’s electrical activity. Changes in your heart’s rhythm can hint towards Irukandji syndrome, so this test helps rule out heart-related issues. Your doctor may also want to test for certain enzymes that point towards any heart damage, which can occur with this disease.
Additionally, a chemistry panel, including a renal function test, can be conducted to see if any kidney damage has occurred. Another test may involve checking your serum lipase levels as one of the complications of this syndrome can be pancreatitis, inflammation of the pancreas.
Your doctor may also use a chest X-ray to see the degree of any fluid accumulation in your lungs or determine the cause of chest pain or difficulty breathing. If you’re presenting signs of a severe headache or changes in your mental state, a computed tomography (CT) scan of your brain might be suggested. This can identify complications like cerebral edema (brain swelling) or intracranial hemorrhage (bleeding inside the skull), which can sometimes occur with Irukandji syndrome.
Overall, your doctor will tailor their approach to your symptoms, but some of the tests in the evaluation of a potential Irukandji syndrome case may include an electrocardiogram, checks for cardiac enzymes, chemistry panel, blood count, liver enzymes, lipase level check, chest X-ray, an echocardiogram (if heart failure is suspected), and a CT scan of the brain.
Treatment Options for Irukandji Syndrome
Currently, there is no special antidote for the venom of C. barnesi or other species known to cause Irukandji syndrome. Treatment is generally supportive, focusing on stabilizing the patient, preventing further venom release into the victim, easing localized venom effects such as pain and tissue damage, controlling systemic effects of the venom, and preventing complications linked to Irukandji syndrome.
If someone is suspected to have been stung, they should be rescued from the water quickly to avoid further stings. They may need immediate life support measures and should be transported to a hospital as soon as possible. Breathing difficulties may require oxygen or other forms of ventilation.
To prevent further venom release, undischarged venom sacs, or nematocysts, need to be deactivated or removed. Household vinegar, or acetic acid, is traditionally recommended to treat the stinging area. It can deactivate undischarged venom sacs of several species. But care should be taken. In some regions, like the United States, applying vinegar might actually trigger more venom release. Other methods of removal include washing the stinging area with seawater or applying gentle pressure using a credit card or similar object.
To alleviate local venom effects, heat application or topical lidocaine could help reduce the pain. However, the use of lidocaine has only been studied in two subjects, the authors themselves, so its routine use for pain caused by these species is not firmly established.
The severe pain associated with Irukandji syndrome often necessitates opioid pain relief, usually given through an intravenous drip. Fentanyl is typically preferred due to its lower likelihood to cause cardiovascular collapse and low blood pressure.
Systemic effects such as high blood pressure are often treated with nitroglycerin, a potent and adjustable blood vessel dilator. In severe cases, nitroglycerin can help manage life-threatening fluid buildup in the lungs. Benzodiazepines, medications that reduce anxiety and induce calmness, can also be used as an add-on treatment for pain and hypertension in Irukandji syndrome.
There has been some discussion about using magnesium sulfate for Irukandji syndrome because it is effective in several other conditions where the nervous system is overstimulated. However, evidence of its effectiveness for Irukandji syndrome is contradictory, so it is not universally recommended.
Some treatments are not recommended for Irukandji syndrome. These include urine, which can actually trigger venom release, worsening the patient’s condition; the antivenom for the box jellyfish C. fleckeri, which has not shown any usefulness for Irukandji syndrome; and beta-blockers, medications used to manage high blood pressure, due to the potential danger of significant low blood pressure.
What else can Irukandji Syndrome be?
The symptoms of Irukandji syndrome can resemble those of many other medical conditions. Therefore, a patient’s history is vital in diagnosing the syndrome and differentiating it from other possibilities. If the patient is found in an area where the creatures causing Irukandji syndrome, a type of jellyfish, are prevalent, the chances of having the syndrome are higher compared to other jellyfish stings.
There are also other conditions that could potentially cause similar symptoms, including :
- Stings from other jellyfish (other cnidarian stings)
- Overdose or misuse of drugs that simulate the nervous system (sympathomimetic toxicity)
- Failure of the heart to pump sufficient blood (acute decompensated heart failure)
- An overactive thyroid (hyperthyroidism)
- A severe allergic reaction (anaphylaxis)
- A condition in which muscle tissue breaks down, releasing damaging proteins into the blood (rhabdomyolysis)
- Inflammation of the pancreas (pancreatitis)
- Poisoning from a black widow spider bite (black widow envenomation)
- A rare tumor of the adrenal glands which can cause high blood pressure (pheochromocytoma)
- Conditions that reduces blood flow to the heart (acute coronary syndrome)
- Health problems resulting from a rapid decrease in pressure too quickly after a dive (decompression illness)
What to expect with Irukandji Syndrome
Irukandji syndrome, a condition caused by certain jellyfish stings, is generally extremely painful and often requires strong painkillers and hospital treatment. However, this condition is usually not life-threatening, especially if treatment is started quickly. Even though some jellyfish have the capability to cause Irukandji syndrome, not every sting will necessarily lead to it.
In fact, most people, who come to the emergency department after being stung, can usually go home within 24 hours of their arrival. That’s why it’s essential to reach out to medical professionals promptly if you believe you might have been stung by a jellyfish capable of causing Irukandji syndrome.
Possible Complications When Diagnosed with Irukandji Syndrome
Complications of severe conditions can include heart damage, indicated by increased heart enzymes, heart disease with sudden fluid in the lungs, heart failure causing shock, and rapid heart rate. In some extreme cases, breathing failure can occur necessitating the use of a machine to aid breathing and admission into intensive care.
The first two recorded deaths linked to the Irukandji syndrome were both due to bleeding in the brain. It is thought to have occurred as a result of severe high blood pressure. It’s worth mentioning that in one of these cases, the patient had been taking a blood-thinning medication called warfarin and had a high measure of blood thinning (INR of 4.9), which likely increased the risk of bleeding.
Although rare, inflammation of the pancreas, painful prolonged erection, and sudden kidney failure have been reported.
While most people experience pain relief within 24 hours, some may have a return of pain after 24 hours, leading to repeated hospital visits. In an isolated case, pain recurrence was noted up to one year later.
- Heart damage
- Heart disease
- Fluid in the lungs
- Heart failure causing shock
- Rapid heart rate
- Breathing failure
- Bleeding in the brain
- High blood pressure
- Pancreas inflammation
- Prolonged erection
- Sudden kidney failure
- Recurring pain
Preventing Irukandji Syndrome
Teaching people about how to prevent Irukandji syndrome is extremely important. People living in areas where the jellyfish that cause this syndrome are common often know about the risks and how to protect themselves. However, travelers from other places frequently get stung and end up suffering from Irukandji syndrome because they aren’t aware of these precautions.
Travelers should know that using “stinger-resistant” nets, which usually protect against other types of jellyfish, doesn’t work against the species that cause this syndrome. These nets aren’t as effective because the jellyfish involved in Irukandji syndrome are too small.
If you’re planning to swim, it’s best to wear a full-body lycra “stinger suit”. These suits reduce your risk of getting Irukandji syndrome by lowering the total area of your body that’s exposed to potential stings.
However, even these suits can’t completely eliminate the risk of getting the syndrome because the jellyfish only need to sting an exposed part of your body once to potentially cause the condition. So, the best way to prevent Irukandji syndrome is to avoid swimming in waters where these specific jellyfish are commonly found.
