The family Scorpaenidae (Scorpionfish) contains around 45 genera and 380 species. Scorpionfishes have large, heavily ridged heads and venomous spines on their back and fins. They are generally well camouflaged with tassels, warts and colored specks and some scorpionfishes (but not stonefish) can change their color to better match their surroundings. Most scorpion fishes live on or near the bottom of the ocean floor and can be found all around the world including from the Red Sea, Pacific Ocean, Australia, Hawaii and the Caribbean.
They feed on crustaceans, cephalopods and fishes employing a lie-in-wait strategy, remaining stationary and snapping prey that comes near. With their mouth they create a vacuum and suck prey in during a nearly imperceptible split-second movement (15 milliseconds).
Scorpionfishes are not aggressive, but if threatened they will erect their dorsal spines. If danger continues they flee, usually very fast but only for a short distance and then quickly settle back and freeze. The stonefishes for example usually bury themselves in sand or rubble using a shoveling motion of their pectoral fins. In a matter of less than 10 seconds only the dorsal portion of the head remains exposed, some sand is thrown on top to further enhancing concealment.
Scorpaenidae family includes:
- Stonefish (Synanceia verrucosa and Synanceia horrida) – the worlds most venomous fish
- Lionfish or Turkeyfish (Dendrochirus and Pterois)
- Stingfish (Choridactylus)
- Spiny devilfish (Inimicus didactylus)
- Devilfishes (also called sea goblins, bearded ghouls and demon stingers) have very special pectoral fin rays that can be moved independently from the rest of the fin. This looks as if the devilfish was walking over the ground. Devilfishes occur on sand and mud bottoms close to reefs and in seagrass meadows. They often bury themselves in the substrate.
Stonefish (Synanceia verrucosa)
The stonefish is the worlds most venomous fish. Stonefish are extremely well camouflaged reef fish found in the waters of northern Australia. Their dorsal spines contain venom, which is injected when external pressure is applied. It is extremely difficult to see because it usually buries most of its body under sand or rubble and only their widely separated eyes show. Often algae and hydroids grow on its back. There is some suggestion that stonfishes exude a white, milky substance over their bodies which encourages plant growth. Their near perfect camouflage and the venomous spines make them a hazard for swimmers, snorkelers and divers in shallow water.
- Rhinopias scorpionfishes are extremly well camouflaged und thus rarely found. The Rhinopias godfreyi (Godfrey’s scorpionfish) is only found in waters of Western Australia (e.g. Shark Bay) and Papua New Guinea
Lionfish or Turkeyfish (Dendrochirus and Pterois)
- Join in packs and use their poisonous feather-like pectoral fins like a net to round up smaller fish and then swallow them.
- The rays of the fins and dorsal ridge are highly poisonous!
Toxin and Clinical Presentation
The venom contains pre and postsynaptic neurotoxins, vascular permeability factors, tissue necrosis factors (hyaluronidase) and stonustoxin (vasodilator). Following envenoming the affected individual presents with
- Immediate severe pain at the sting site
- Local swelling, bruising and puncture marks. A remnant of the spine(s) may be left in the wound
- Systemic envenoming is rare, and there are no reports of deaths in Australia. Non specific features of envenoming include nausea, vomiting, dizziness and dyspnoea. Cardiovascular signs such as hypotension, bradycardia, collapse, pulmonary oedema and cyanosis are rarely reported.
- Other fish stings
- Stingray injury.
- Reassure the patient, and give simple oral analgesia such as paracetamol
- Immerse both limbs in hot water. The unaffected limb is immersed to ensure the water temperature is tolerable and so prevent burns [particularly important after local anaesthetic administration]
- Do not apply a pressure immobilisation bandage (PIB)
- Transport all patients with significant pain refractory to first aid, or systemic symptoms to a medical facility
Resuscitation and supportive care
- Stonefish envenoming is a very painful but rarely life threatening
- Treatment is essentially supportive
- Continue hot water immersion
- Give IV morphine 0.1 mg/kg (up to 5 mg), repeated every 10minutes until patient is comfortable
- Consider regional anaesthesia (e.g. foot block or wrist block) with a long acting local anaesthetic agent (e.g. ropivicaine)
CSL Stonefish Antivenom is used in the treatment of severe pain refractory to first aid, IV opioid analgesia and regional block and/or systemic envenoming. This equine IgG Fab is the definitive treatment of envenoming by stonefish (Synanceia trachynis and Synanceia verrucosa) from Australian waters. It may also have a role in the treatment of bullrout (Notesthes robusta) stings, and for other species within the Scorpaenidae family.
- Give one ampoule (2000 units) for every two spine puncture wounds (to a maximum of three ampoules), undiluted by intramuscular injection or diluted in 100 mL normal saline over 20 minutes.
- It is not known whether Stonefish Antivenom is more efficacious by the IV or IM route
- No absolute contraindications
- Pregnancy and lactation: No restrictions on use
- Paediatric: Give standard adult dose in 10 mL/kg of normal saline.
- There is an increased risk of anaphylaxis in patients who have been previously treated with antivenom or who have a known or suspected equine sera allergy.
- Place the patient in a monitored area where equipment, drugs and personnel are available to manage an allergic reaction
- Administer one ampoule for every two spine puncture wounds (to a maximum of three ampoules) undiluted by intramuscular injection. Alternatively the antivenom may be diluted in 100 mL normal saline and administered intravenously over 20 minutes
- Premedication with adrenaline is unnecessary
- Repeat doses of one ampoule are given until therapeutic end point is achieved (see below)
- Note: It may be given as a rapid IV push if the patient is haemodynamically unstable or in cardiac arrest.
- Therapeutic end point
- Resolution of local and systemic features of envenoming.
Adverse drug reactions and management
- Acute allergic or anaphylactic reaction
- Immediately cease antivenom infusion
- Give oxygen, IV fluids and administer IM adrenaline 0.01 mg/kg(max 0.5 mg) to lateral thigh
- Serum sickness
- This relatively benign and self limiting complication may occur 5–10 days after antivenom
- Manifestations include fever, rash, arthralgia and myalgia
- Oral steroids (e.g. prednisolone 50 mg/day or 1–2 mg/kg/day in children for 5 days) ameliorate symptoms
- Note: All patients should be warned about this potential complication prior to discharge.
- Failure to give repeat doses of antivenom following an absent, incomplete or transient response to the initial dose
- Withholding antivenom from the envenomed child or pregnant woman because of concerns about the potential adverse reactions
- Administration of antivenom to a patient who has not been envenomed.
- Relative efficacy of intramuscular versus intravenous route of administration.
- Patients without clinical features of systemic envenoming at 2 hours do not require further medical observation
- Patients treated with opioid analgesia or antivenom may be discharged when they have been asymptomatic for a period of 4hours.
- White J. CSL Antivenom Handbook 2001. CSL Ltd: Parkville, Melbourne, Victoria. [Reference]
- Lee JYL, Teoh LC, Leo SPM. Stonefish envenomation of the hand – a local marine hazard. A series of 8 cases and review of the literature. Annals of the Academy of Medicine, Singapore 2004; 33:515–520. [fulltext pdf]
- Little M. Stonefish (Synanceia species) sting. Emergency Medicine 1990; 2(4):5.
- Sutherland SK, Tibballs J. Australian animal toxins: the creatures, their toxins and care of the poisoned patient. South Melbourne: Oxford University Press, 2001.