Funnel Web Spider

The Funnel Web spider is the most venomous spider in Australia with 14 confirmed deaths on record. The Funnel Web spider is widely distributed throughout south-east Australia with at least 35 species in 2 genera (Atrax  and Hadronyche). The spider is typically large, black or brown and robust with stout legs and large fangs. They usually like in the ground with a characteristic funnel shaped web at the entrance to the burrow that provides the duel role of ensnaring pray and advising of an approaching mate.
Funnel Web Spider Funnel Web Spider

The Funnel Web spider is particularly aggressive and will rear up on its hind legs to strike if threatened. Female spiders rarely leave their burrows but the male spider will often leave their retreat in search of female mates and as such is more frequently responsible for human bites.

Funnel Web Spider venom

The venom consists of multiple components but the main toxin responsible for human poisoning (robustoxin) is found only in male spiders. Although minimally toxic to many animals, in humans it causes stimulation of the nervous system with rapid and potentially devastating effects.

Symptoms of envenomation

The Funnel Web Spider has large fangs and an acid venom and the bite is usually very painful. Progression of symptoms of envenomation may be very rapid. Initial symptoms include tingling around the lips, twitching of the tongue and copious saliva production. This may be followed by generalised muscle twitchingand jerking. In severe envenomation, the victim will develop difficulty breathing and may even develop frothing at the lips progressing to respiratory and cardiac arrest.
Treatment

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 Funnel Web Spider envenomation should receive pressure immobilisation of the affected limb.

If the spider has been caught (ensuring no risk involved) it should be transported to the hospital with the victim to assist with identification

Antivenom

CSL Funnel Web Spider Antivenom is specific for neutralising the venom of the Atrax Robustus  (Sydney Funnel Web) but is effective against most of the group of Australian FunnelWeb Spiders and also against the venom of the Mouse Spider (Missulena sp.). The freeze dried antivenom which is reconstituted with sterile water provided is produced from Rabbit 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. Although anaphylaxis to the antivenom is rare, capacity to manage anaphylaxis must be available.

The antivenom is administered as a slow intravenous push. The initial dose is two ampoules if moderately symptomatic and four ampoules if severe envenomation. The dose should be repeated as required according to response to treatment. There are case reports documenting requirement of eighteen ampoules of antivenom following life threatening envenomation.

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.