Marine Envenomation


Marine envenomation can result from stings, due to contact with nematocysts, or penetrating injuries from spiny fish, stingrays and sea urchin.

Topics addressed in this module are:

  • Box Jellyfish stings
  • Irukandji stings
  • Blue bottle stings
  • Venomous fish injuries
  • Stingray injuries
  • Sea urchin injuries
  • Blue ringed octopus stings

Box Jellyfish

Box jellyfish are found north of the Tropic of Capricorn.1 Envenomation is potentially fatal due to rapid cardiorespiratory collapse.

Risk Assessment

Severe local pain is typical with the development of erythematous linear eruptions at the sting site.

Delayed hypersensitivity reactions along the sting sites occur in over half of the cases.1 Confirmation of the sting can be done by placing sticky tape over the sting sites – which removes nematocysts – which are visible under a microscope.


Cardiorespiratory collapse associated with Box Jellyfish envenomation is typically immediate. This means that almost no one with life threatening envenomation reaches the hospital alive unless ACLS has already been instituted.1 Standard ACLS algorithm should be employed. Antivenom is available however its effectiveness is not proven. Its administration should not detract from good ACLS. There may be a role for magnesium in unresponsive cases.

It is important to remove any tentacles and apply liberal amounts of vinegar which is thought to inactivate remaining undischarged nematocysts. Recent bench top studies have brought into question the efficacy of vinegar therapy, however at this stage it is still considered standard therapy. Adequate analgesia is important.

Irukandji Stings

Irukandji syndrome is typically reported after stings by the Carukia barnesi jellyfish, but other jellyfish can cause the syndrome. It is most commonly reported in northern Australia.

Risk Assessment

Irukandji syndrome has minor local effects but is characterised by severe generalised pain and autonomic instability (hypertension, tachycardia, sweating and anxiety) which develops 20 to 30 minutes after the sting. Severe envenomations can result in cardiotoxicity with myocardial depression, pulmonary oedema and cardiogenic shock. An ECG and troponin should be performed2. An echo may also be helpful.


Provide adequate analgesia. Parenteral narcotics are often required. Intravenous magnesium has been used as an analgesic adjunct but there is no evidence to support its use3. The generalised pain usually takes 6 to 12 hours to resolve. Supportive care is necessary if there are signs of cardiotoxicity, these symptoms can persist for 2-3 days. Clonidine at 1mcg/kg IV has been used with anecdotal success4.

Bluebottle Stings

Bluebottle stings are benign. They cause immediate localised pain which typically lasts for about one hour. Erythema and a linear eruption at the sting site is common and may last for days. Remove any tentacles and immerse the area involved in hot water (450C) for 20 minutes. The venom is heat labile and the hot water is thought to inactivate the venom. 

Venomous Fish Injuries

Puncture wounds from fish with venomous spines cause localised oedema, erythema and pain which can be severe. Examples of this group include catfish, stonefish and scorpion fish. Management involves hot water (450C) immersion for up to 90 minutes. Oral or parenteral analgesia may be necessary. Regional nerve blocks may be considered, but need to be used cautiously in combination of hot water therapy.

All wounds must be thoroughly irrigated and any foreign body removed.

Stonefish antivenom is available in some centres for pain not controlled by these measures, however there is no evidence supporting its effectiveness. Ensure adequate tetanus prophylaxis. The role of prophylactic antibiotics is unclear. The wound will need to be reviewed regularly to ensure infection does not develop.

Stingray Injuries6

Stingray injuries are similar to venomous fish injuries except there is typically more trauma with the sharp body spine often lacerating tissues, and there is a high risk of barbs being retained in the wound. These are not well visualised on an X-ray, despite being radio-opaque, but are seen on ultrasound. Deep wounds should have a formal washout ± debridement in theatre. There may be a better case for routine antibiotic prophylaxis for stingray injuries, however there is no good evidence for the same. Management of pain again involves hot water immersion, analgesia ± regional anaesthesia. Ensure adequate tetanus prophylaxis.

Sea Urchin Injuries

Sea Urchin injuries are typically from non-venomous spines, however these are very chalky and fragile, breaking off and leading to foreign bodies which are difficult to remove. Venomous spines are much less common causing more prominent pain which should be managed as per other penetrating venomous marine injuries. Surgical removal of embedded spines may be necessary.

Blue ringed Octopus

The blue ringed octopus has tetrodotoxin in its saliva which is injected when it bites2. This results in paralysis which can be life threatening. Pressure bandage immobilisation should be applied in the first instance and supportive management, including ACLS provided.2

Further reading


  1. Isbister G. “Managing injuries by venomous sea creatures in Australia.” Australian Prescriber 2007;30:117-21
  2. Berling I and Isbister G. “Marine Envenomations.” Aust Fam Physican 2015;44(1): 28-32
  3. McCullagh N et al. “Randomised trial of magnesium in the treatment of Irukandji syndrome.” EMA 2012; 24: 560-5
  4. Little M and Somerville A. “Clonidine to treat Irukandji Syndrome” EMA 2016; 28(6):756-7
  5. Currie, B & Jacups S. “Prospective study of Chironex fleckeri and other box jellyfish stings in the Top End of Australia’s Northern Territory.’ MJA 2005;183:631-6
  6. Clark R et al. “Stingray Envenomation: A retrospective review of clinical presentation and treatment in 119 cases.” JEM 2007;33(1):33-7