by Snakes Incorporated » Tue Dec 13, 2005 1:13 pm
About Funnel web Spiders
There are several species of funnel web spider found throughout Australia. The best known of these is the Sydney funnel web spider, Atrax robustus. The male of this species is Australia's most dangerous spider, and is capable of causing death in as little as 15 minutes. It is found only within a 160 km radius of Sydney, although related species have been described all along the east coast of Australia, and one of these, the northern or tree-dwelling funnel web spider (Hadronyche fomidabilis), has been shown to be dangerous to man. The Sydney funnel web is a large, black aggressive spider with large powerful fangs. It lives in burrows or crevices in rocks or around house foundations, lining the burrows with silk. Colonies of more than 100 spiders may be found. The male spiders in particular tend to wander into houses in the summer, especially in wet weather. It is unusual amongst spiders in that the male appears to be more dangerous than the female. It is also of note that the venom appears to particularly affect primates, whereas other mammals are relatively resistant.
Several other funnel web spiders species have been described throughout Australia, including the northern or tree-dwelling funnel web (Hadronyche formidabilis), found in northern New South Wales and southern Queensland, as well as species found in Victoria, South Australia and Tasmania. There is little information on the toxicity of most of these spiders' venoms, and the danger they may pose to man.
Funnel web Spider bite in Australia
Prior to the introduction of Sydney funnel web antivenom in 1980, there had been 13 known fatalities associated with bites from this spider. Since the antivenom has been in use, no deaths have been recorded, and time spent by bite victims in hospital has been greatly reduced. Most bites occur in the warmer months, and are predominantly sustained on the extremities. The pressure immobilisation method of first aid should be employed for bites by any large black spider in the Sydney area, since the illness caused by funnel web bites may be rapidly progressive and death may ensue within minutes to hours. Children are especially at risk, due to their lower body weight and the potential for multiple bites to occur if the spiders are handled.
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Symptoms and Signs of Envenomation by Atrax robustus
In most cases of bites by this spider, little venom is injected and no symptoms develop. None the less, first aid should be promptly applied and medical attention sought without delay. If envenomation has occurred, the bite site may be extremely painful, although tissue necrosis is not seen. There is some evidence that prolonged immobilisation of venom in the tissues may lead to inactivation. Systemic symptoms can develop within minutes if effective first aid is not employed. They are due to the effect of atraxotoxin’s direct effect on nerves leading to the widespread release of neurotransmitter from somatic and autonomic nerves.
Symptoms and signs of envenomation include:
Numbness around the mouth and spasms of the tongue
Nausea and vomiting, abdominal pain, acute gastric dilatation
Profuse sweating, salivation, lacrimation, piloerection
Local and generalized muscle fasciculation and spasm, commencing in facial tongue or intercostal muscles, and including trismus, which may necessitate paralysing the patient with muscle relaxants in order to manage the airway
Dyspnoea
Confusion, irrationality, coma which may persist in the presence of normalized ventilation, oxygenation and blood pressure, and may be related to raised intracranial pressure
Hypertension, vasoconstriction, tachycardia and cardiac arryhthmias ? related to release and subsequent depletion of neurotransmitter
Widely dilated pupils, which may be fixed
Acute non-cardiogenic pulmonary oedema
Later, the severely envenomed patient may develop progressive hypotension and apnoea. These features may relate to depletion of neurotransmitter.
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Don’t kill it, if you are not planning to eat it.