Basics :: Spiders :: Snakes :: Marine :: Others
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.
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.
Redback Spider
The Australian Red Back Spider (Latrodectus hasselti) is a close relative of the American Black Widow Spider (the main difference being the presence of a red stripe on the spiders back). It is widely distributed throughout Australia in essentially all habitats and is common in urban areas. The spider typically builds webs under objects and in dry, sheltered spaces (seats / shelves / fence lines etc) and has drop lines to the ground. Only the female Red Back Spider is dangerous to humans. The female spider does not wander far from its web and unlike the funnel web spider, is not aggressive with most bites occurring during summer months when people make contact with the web.
Red Back Spider venom
Of the multiple toxins that make up the female red back spider venom, the component most responsible for symptoms in humans is the latrotoxin. This toxin causes excessive stimulation of nerve pathways throughout the body with a wide range of effects sometime referred to as ‘latrodectism’.
Symptoms of envenomation
Although the bite is frequently very painful, it is rarely lethal.
- Localised symptoms. Due to the small fangs, the spider bite is often painless and puncture marks may not be visible. Intense burning pain is usually felt within 5 minutes at the bite site and the characteristic finding of a raised welt with small drops of overlying sweat will confirm the diagnosis. The pain will frequently extend up the limb with resultant tenderness over lymph glands in the groin or arm pit
- Generalised symptoms. The pain may spread to the abdomen or chest and if this occurs is often associated with profuse sweating, nausea and occasionally vomiting. In very severe cases it may cause muscle weakness and tremor and is frequently responsible for elevated blood pressure and rapid and irregular heart beat.
Treatment
In the Field
The principles of general First Aid should be followed. The pressure immobilisation technique should not be applied as this will not inhibit spread of the venom and may cause an increase in pain at the bite site. Ice may be applied to the bite site to reduce pain.
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 Red Back Spider Antivenom is for neutralising the venom of the Australian Red Back Spider but has shown to be effective against most of the black widow group of spiders. It is produced from Horse serum.
The antivenom should only be administered if there is clear evidence of severe symptoms of envenomation that fail to respond to simple treatment measures (pain relief / ice etc). 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 uncommon, anaphylaxis to the antivenom can occur and the capacity to manage anaphylaxis must be available.
The antivenom may be administered as intravenously or intramuscularly push. Recent evidence suggests the intravenous route may be more effective. The initial dose is one ampoule. The dose should be repeated as required according to response to treatment. It is uncommon to need to give more than three ampoules.
There are many case reports of the antivenom having dramatic effect when given up to a week or more following the bite
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 6 hours following antivenom administration to ensure no side effects
- The victim should receive advice on the potential to develop serum sickness if multiple doses of antivenom were required.
