Sea Snake Envenomation

There are more than 30 different species of sea snakes, all potentially dangerous to humans, in tropical northern Australian waters alone. All are elapid snakes, and thus related to the Australian land snakes. These snakes all feed on fish and spend some or all of their time at sea.

Sea Snake Venom

The multicomponent venoms contain two main groups of active toxins – neurotoxins and myolysins.

Symptoms of envenomation

Sea snakes typically own numerous teeth additional to their fangs and bite sites will often demonstrate multiple puncture wounds. The bite is not overly painful and does not generate a vigorous swelling or bruising response.

Neurotoxin exposure will typically present with onset of symptoms within 6 hours of the bite. Drooping of the eyelids and double vision are early features and paralysis may progress over time to involve the limbs and eventually weakness of muscles required for breathing.

Myolysin exposure will present as pain over affected muscles which is worse with movement and this will progress on to muscle weakness. The urine may become very dark from the excretion of proteins from damaged muscle cells. If not recognized and treated this will then lead to kidney failure

First Aid in the field

The principles of first aid in the field are to minimise the spread of venom into the blood stream while awaiting transfer to expert medical care. In addition to General First Aid principles, any suspected victims of Sea snake envenomation should receive pressure immobilisation of the affected limb.

No attempt should be made to capture or kill the offending snake. The presence of the snake rarely assists the medical team treating an envenomation as identification requires expert skill. Additionally, the usual outcome of inexperienced hands trying to capture a venomous snake is ……….. a snake bite!

Antivenom

CSL Sea Snake Antivenom is developed from the venom of the Beaked Sea Snake and Australian (land) Tiger snake however has been shown to beeffective against a wide variety of venomous sea snakes. The antivenom is produced from horse serum.

The antivenom should only be administered if there is clear evidence of symptoms of envenomation. It may be administered in the field but must be administered by experienced medical personnel and all victims of envenomation require transport to hospital. The risk of anaphylaxis to the antivenom is moderately high and although pretreatment with adrenaline and antihistamines is not indicated, capacity to manage anaphylaxis must be available.

The antivenom is administered as an intravenous infusion over 15-30minutes. The initial dose is between one to three ampoules depending on the severity of symptoms. The dose should be repeated as required according to response to treatment.

If specific sea snake antivenom is unavailable, CSL Tiger Snake antivenom may be used as a substitute however double the volume of this antivenom may be required for the same clinical response. As with all land snake envenomations, CSL Polyvalent Snake Antivenom is a potential substitute

Following antivenom

• The tetanus immunisation status of the victim should be checked and updated if necessary
• The victim should be observed for a minimum of 12 hours following full resolution of symptoms of envenomation
• The victim should receive advice on the potential to develop serum sickness