CLINICAL PRACTICE • Envenomation The funnel web and common spider bites

B Nimorakiotakis, MBBS, FACEM, is Staff Specialist, Epworth Hospital and Sunshine Hospital, and Fellow, The Australian Venom Research Unit, Department of Pharmacology, the University of Melbourne, Victoria. KD Winkel, MBBS, BMedSc, PhD, FACTM, is Director, The Australian Venom Research Unit, Department of Pharmacology, the University of Melbourne, Victoria, and President-Elect, the Australasian College of Tropical Medicine.

BACKGROUND Spider bites are one of the commonest Sydney funnel web spider The funnel web spiders, encompassed types of bites or stings presenting for man- within the genera Atrax and Hadronyche, agement in general practice and emergency The spider responsible for the most signifi- are the most dangerous spiders in the medicine departments. While in most cases cant bites is the Sydney funnel web spider world. Although the incidence of the responsible species is not identified and (Atrax robustus), a species geographically envenomation is low, funnel web spiders the effects self limited, certain species can limited to an area within 160 km radius of remain a cause of considerable public inflict life threatening bites. the Sydney (New South Wales) central busi- concern. However, most common spider ness district.1 The Sydney funnel web bites produce only minor effects requiring Funnel web spiders spider is a large spider with a glossy black only symptomatic treatment. More than 30 species of the highly danger- cephalothorax and a dark abdomen. The OBJECTIVE ous funnel web spiders are found on the female is larger and more robust than the This article describes the clinical features eastern seaboard of Australia including parts male (Figure 2). The male has a spur on its and treatment of the funnel web spider of South Australia and Tasmania (Figure 1). second leg and the spinnerets (from which and that of its close relative, the mouse The venom appears to be particularly harmful the spider produces silk) of both sexes are spiders. It also covers the question of necrotising arachnidism as well as bites to primates, whereas other mammals are rel- long and obvious, especially the terminal from other common species of spiders. atively unaffected. While many of these spinneret. Both sexes of this species are spiders remain unnamed and the venom very aggressive. When disturbed, they will DISCUSSION unstudied, all funnel web spiders belong rear up ready to strike with their large, Appropriate first aid combined with the either to the genera Atrax or Hadronyche. downward pointing fangs. The female administration of specific antivenom can be Identification and classification of funnel web spider constructs a burrow that may be 30 life saving for funnel web spider bites. True necrotising arachnidism appears to be rare. spiders is often difficult – with some species cm or more deep. Some use crevices in If suspected, clinicians must first consider resembling the less dangerous trapdoor rocks or around house foundations and the very wide differential diagnoses. spiders. Any suspicious spider that has colonies may contain as many as 100 inflicted even an apparently minor injury spiders. The male spiders tend to roam and within the geographic distribution of these often enter houses, particularly during the spiders should be treated as if it were a summer months and in wet weather. Bites funnel web spider. If the spider is captured or may occur when the spider has taken up killed, formal identification is encouraged – temporary residence in bedding, clothing or even a badly damaged spider can often be footwear, or when it is trodden on. successfully identified by arachnologists. Most bites occur in the warmer months, and are predominantly sustained on the

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Figure 2. Comparison of size and appearance of Figure 3. Female Northern funnel web spider male (left) and female (right) Sydney funnel web Photo courtesy Vern Daffin Figure 1. Geographical distribution of funnel web spiders Photo courtesy Vern Daffin spiders Ç-atracotoxins (Ç-ACTXs). The Ç-ACTXs act • hypertension, tachycardia and vasocon- extremities. Children are especially at risk by slowing sodium current inactivation striction (hypotension may occur later) due to their lower body weight and the resulting in spontaneous repetitive firing of • local and generalised muscle fasciculation potential for multiple bites to occur if spiders action potentials.7 This triggers the release and spasm which may be prolonged and are handled. However, considering the large of excessive – and eventual exhaustion of – violent (facial, tongue or intercostal population at risk, effective envenomation is predominantly sympathetic neurotransmit- muscles, trismus) and difficult to manage. very uncommon. The male species is consid- ters leading to the characteristic biphasic Phase 2 is characterised by: ered to be the most venomous, and all clinical syndrome. • hypotension 13 funnel web spider fatalities documented • hypoventilation and apnoea before the introduction of antivenom in 1980 Symptoms and signs of • continuing acute noncardiogenic pul- have been attributed to the male spider.1 envenomation monary oedema Sydney funnel web spiders are usually easily The initial bite is usually painful and fang • coma, and, finally identifiable to the trained eye, but any large marks are generally seen. The envenomation • irreversible cardiac arrest. dark spider found in the geographic distribu- syndrome is generally characterised by two tion area should be treated with suspicion. phases: the first begins within minutes of the First aid and treatment bite, and the second when the secretions A summary of the recommended first aid and Other funnel web spiders subside – typically many hours later.1 medical treatment for funnel web spider bite There are 12 described species and at least Historically deaths have occurred in either is presented in Figure 4. The key points are: 20 unnamed species in the more widely dis- phase of envenomation. • ensure airway, breathing and circulation tributed genus Hadronyche.2,3 They are also Phase 1 is characterised by: (ABCs) are maintained aggressive spiders with at least six species Local effects: • prompt application of pressure immobilisa- described as having a similar envenomation • bite site may be painful for days to weeks tion bandage (PIB) to the affected limb syndrome to the Sydney funnel web spider.4 because of direct trauma and acidity of venom • transfer to hospital, ideally where As the potency of Hadronyche spp venom but no local necrosis has been recorded antivenom, resuscitation equipment and appears variable in relationship to sex, size, • local swelling, erythema and occasionally monitoring is available health, feeding habits and geographical dis- sweating. • intravenous access should be obtained tribution, all bites from these spiders should General effects: • PIB should be removed only in an area be managed as for the Sydney funnel • numbness around the mouth and spasms/ were appropriate resuscitation can occur web spider. fasciculation of the tongue and antivenom is available. (If PIB has • nausea and vomiting, abdominal pain, been removed and the patient deterio- Pathogenesis acute gastric dilatation rates it should be re-applied) Although most funnel web spider bites are • profuse sweating, salivation, lacrimation, • local tissue enzymes may inactivate the thought to be ineffective or ‘dry’, the clini- piloerection venom, therefore the use of PIB may not cal syndrome can be devastating and has • severe dyspnoea as a result of noncardio- only be helpful in delaying the onset of been lethal in both adults and children. genic pulmonary oedema symptoms, but may allow for a degree of While the causative venom is multicompo- • mental status can rapidly progress from inactivation of the venom nent, the key neurotoxins are the confusion to irrationality or coma • administer antivenom as per protocol in

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Figure 4 if systemic signs of envenoma- caution in the event of hypotension antivenom in 1980, there have been no deaths tion are present because of noncardiogenic pulmonary reported and time required in hospital has dra- • until antivenom is available supportive care oedema matically decreased from an average of 14 days8 of the envenomed patient may include: – relapse is possible and may manifest to less than 2 days.1 Moreover, the antivenom is – supplemental oxygen as dyspnoea secondary to noncardio- extremely safe – no cases of anaphylaxis have – atropine (0.6 mg initial dose for an adult) genic oedema which usually responds been reported and only one case of serum sick- to reduce salivation and bronchorrhoea to further antivenom (this should not ness has been associated with the antivenom.9 – nasogastric aspiration because of be confused with iatrogenic pulmonary gastric dilatation oedema as a result of intravenous Mouse spiders – muscle relaxants and sedatives to facil- overload, particularly in children) Mouse spiders (Missulena spp) are medium itate mechanical ventilation and control • if no symptoms or signs of envenomation sized and robust spiders found throughout intracranial pressure have started 4 hours after the removal of first mainland Australia. Currently there are – intubation and ventilation for respiratory aid measures or postbite, the patient may be 11 recognised species. They possess large failure and to reduce intracranial pressure discharged (most patients presenting to hos- powerful fangs and produce copious (note: entotracheal intubation can be diffi- pital will not have been envenomed) amounts of venom, but systemic envenoma- cult as a result of excessive salivary • tetanus status should be assessed and tion has rarely been reported and bites are secretions and violent fasciculations) prophylaxis provided if indicated. generally minor. The most severe case of – fluid resuscitation should be used with Since the introduction of funnel web spider mouse spider envenomation presented simi-

Should be considered in all cases of envenomation by a suspected funnel web or mouse spider Apply pressure immobilisation bandage (PIB) to affected limb ASAP PIB is not to be removed until intravenous access is established and appropriate monitoring and antivenom is available Note: Antivenom should only be given if full facilities for treating an anaphylactic reaction, including resuscitation and monitoring equipment, are available

Administer 240 units (two ampoules) of funnel web spider antivenom intravenously if systemic signs of envenomation. If the patient has severe signs and symptoms of envenomation four ampoules should be administered intravenously.2 Adrenaline should be ready in case of anaphylaxis (although it has never been reported)

Once antivenom is given Patient does not respond, or only Administer two further vials antivenom and patient has improved partially responds, to antivenom within remove PIB 15 minutes Observe the patient for at Keep PIB on or re-apply PIB if removed least 12 hours preferably in Good response Poor response intensive care Titrate further antivenom dosage against signs and symptoms. Discharge home if clinically better with the Reconsider the diagnosis but be aware that severe envenomation may require multiple advice to return if: ampoules – in such a case administer two further vials of antivenom (more than eight vials may be required) 1. Symptoms of envenomation recur 2. Symptoms of serum sickness occur Admit patient to intensive care for closer monitoring Ensure tetanus status is up Note: If symptoms recur postremoval of PIB, it should be reapplied until further antivenom has been given. to date Endotracheal intubation may be difficult as a result of excessive salivation and fasciculations

Figure 4. Management of potential funnel web spider bite

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larly to that of the funnel web spider.1 Australia. A summary of some of the more Subsequent research has shown the relevant well known species is presented in Table 1 toxin has a Ç-ACTX-like action and funnel web and management is shown in Figure 6. spider antivenom neutralised its effect in vitro.10 In 1985, an infant bitten in southern Necrotising arachnidism Queensland by a male mouse spider (M. Necrotising arachnidism is the name give to bradleyi, Figure 5) was successfully treated a syndrome of skin blistering, ulceration and with funnel web spider antivenom.1,11 necrosis following spider bite. Although it is However, documented clinical effects of the well recognised in many parts of the world, bite appear generally mild and self limiting it remains little understood. Since the late Figure 5. Male eastern mouse spider and most cases don’t require antivenom.12 1970s doctors have suspected that Photo courtesy Ken Walker, Melbourne Museum Australian spiders may cause local tissue Other spiders injury.15,16 The chief suspects have been the Thousands of species of spiders inhabit white tailed spider (Lampona spp), the black

Table 1. Summary of common spider bites Photos courtesy Ken Walker, Melbourne Museum14

Spider (family) Adult body length Circumstances of bite Local reaction Nausea/vomiting

Huntsman Over 20 mm Handling spiders or Immediate pain may be severe, Low incidence (Sparasside) treading on them local infection may occur

Orb weaver 10–20 mm Bed clothes, garments left Mild pain and redness Low incidence (Araneidae) on clothesline over night

White tail 10–20 mm Bedclothes, garments or Local pain and inflammation No (Lamponidae) shoes left on the floor

Wolf Over 20 mm Exposure in the garden Local pain lasts approx Low incidence (Lycosidae) and near water 10 minutes

Jumping Up to 20 mm Exposure in the garden Local pain lasts approx 20 Low incidence (Salticidae) minutes, local swelling may occur

Black house Up to 20 mm Walking into web Pain usually moderate but may be 1 out of 5 cases (Desidae) severe. Local swelling may occur

Trapdoor Over 20 mm Exposure in the garden Mild pain, short duration, mild Low incidence (Idiopidae and redness Nemesidae)

Tarantula or Over 20 mm Exposure in the garden Pain usually moderate Low incidence ‘whistling spider’ and handling spiders but may be severe (Theraphosidae)

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The 24 hour National Poisons Information line (131 126) can always be used for clinical advice

Patients presenting for the management of spider bite

Suspected redback Suspected funnel web Definite spider bite Suspected spider bite or mouse spider bite or If spider is caught it can be sent to the other bite unidentified large spider Australian Venom Research Unit * for formal identification or taken to local state museums (call before presenting)

Treatment Pressure immobilisation Clean area with soapy water first aid As necrotising arachnidism is an uncommon sequelae the patient Treatment Transfer to hospital should be reassured Icy water for first aid Consider funnel web Tetanus prophylaxis should be undertaken depending on the Consider redback spider spider antivenom patient’s immunisation status antivenom Refer to potential Simple measures should be applied such as: Refer to redback spider funnel web spider bite • icy water management plan management plan • oral analgesia (paracetamol)

Pain Swelling Pruritis Ulcer

It should be noted that, Swelling alone is not an Antihistamines may be Local wound care should in most cases, indication for antibiotics of use as some spider be undertaken, other pain is short lived (which should not be bite venoms may contain causes of ulcers need to routinely given after or cause the release of be considered – spider bite) and there is histamine refer to Figure 7 no clear evidence for the role of topical or systemic steroids *Australian Venom Research Unit, Department of Pharmacology, the University of Melbourne, Victoria (phone: 03 8344 7753)

Figure 6. Guide to the management of spider bites widow or house spider (Badumna spp) and study of 130 bites from one species of In one well publicised international example, the wolf spider (Lyscosidae spp). Thereafter, white tailed spider (Lampona cylindrata) no a 7 month old child admitted to a New York various reports of such lesions were pub- cases of ulceration were reported.24 hospital with the presumptive diagnosis of lished, mostly without the associated spider brown recluse spider bite was later found to 17–21 Is necrotising arachnidism being formally identified. Due to the fre- fact or fallacy? have been suffering from cutaneous quency of spider bite this issue has been of anthrax.27 Various cases of infection, including great interest to clinicians and the public Recent reviews have concluded that other cutaneous anthrax and sporotrichosis, have alike. However, experimental studies of the causes of skin ulcers should be suspected also been reported in the context of possible suspect venoms has not revealed a clear ahead of spider bites as the true incidence of or definite spider bite in Australia. Therefore, mechanism for the proposed skin necro- such lesions appears to be very low not only a history of spider bite doesn’t exclude the sis.22–23 Moreover, in a recent prospective in Australia but also in the United States.25,26 possibility that the true cause of skin necrosis

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It is important to note that necrotising History and examination Investigations arachnidism is an uncommon sequelae Current General of spider bite • History of spider bite • Glucose Management • Single or multiple lesions • Full blood count • Local wound/ulcer care should be • Association with systemic • Urea and electrolytes undertaken in cases of suspected symptoms such as fever • Liver function tests spider bite related lesions • Known environmental exposures • Coagulation studies • Once definitive diagnosis is made • Sexual history • Autoimmune screen treat the underlining problem • Painful or painless • Chest X-ray Follow up • Associated with nodules • Vascular studies • Regular follow up may be required • Progression of symptoms • Others as indicated on as it may take time before the Past clinical presentation diagnosis is made • Previous skin lesions Ulcer site • Photos may be helpful in tracking the • Autoimmune disease • Swab – special media may progress of the ulcer • Diabetes be required. Pathology • Immobility department will need to be • Psychiatric contacted for advice before swab is taken • Skin cancers • Histology (preferably of the • Travel history margin of the ulcer) • HIV • intravenous drug use Medication • Legal and illegal Suspected necrotising arachnidism – spider not positively identified

Figure 7. Guide to the diagnosis, investigation and management of possible necrotising arachnidism

Table 2. Differential diagnosis of suspected in any given case is infective. Managing suspected necrotising necrotising arachnidism The true incidence of necro- arachnidism tising arachnidism in Australia is unknown and at the very least There remains no definitive treatment for • Vascular ulcers: arterial or venous insufficiency uncommon. The usual presen- necrotising arachnidism. It is best to view the • Diabetic ulcer tation for alleged ‘necrotising treatment of such lesions as you would for • Neuropathic ulcers arachnidism’ is of an area of any ulcer requiring local wound care. Specific • Bacterial infections blistering or necrosis, usually on treatment should commence once pathology • Fungal infections the limb, in a patient who has of the ulcer has been established. It should • Viral infections been outside (often in the be noted that the ulcer pathogenesis may • Foreign body garden), but usually without a take time to identify and it is best not to label • Focal and general vasculitis definite bite history or, if a bite the ulcer as necrotising arachnidism until an • Injection of toxin (accidental or deliberate) has been felt, without identifi- extensive examination of the possible differ- • Drug reaction cation of the offending ential diagnosis is made (Table 2, Figure 7). • Physical/mechanical trauma (may be deliberate) creature. The diagnosis of • Bed sores necrotising arachnidism is, Conclusion • Burns (especially chemical burns) therefore, one that must usually Spider bites are a common cause of stress • Contact dermatitis be considered circumstantial for patients and generate time consuming • Pyoderma gangrenosum and care must be taken to work for general practitioners and poison • Neoplasm exclude other treatable causes information centres. However, most cases • Connective tissue diseases of necrotic lesions. A list of are self limiting and can be managed sympto- • ~1 antitrypsin deficiency possible differential diagnoses matically. The exception is the possibility of • Other arthropod bites or stings is given in Table 2. funnel web spiders, all of which should be

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considered potential medical emergencies. venom. Aust J Exp Biol Med Sci spiders. Comp Biochem Physiol 1985;59:555–561. 1991;98:441–444. Although true necrotising arachnidism is rare, 6. Nicholson GM, Walsh R, Little MJ, Tyler MI. 24. Isbister GK, Gray MR. A prospective study of putative cases of necrotising arachnidism Characterisation of the effects of robustoxin, 750 definite spider bites, with expert identifica- should be managed as for any ulcer with a the lethal neurotoxin from the Sydney funnel tion. Q J Med 2002;95:723–731. web spider Atrax robustus, on sodium channel 25. Sandlin N. Convenient culprit: myths surround- combination of local wound care and a search activation and inactivation. Eur J Physiol ing the brown recluse spider. A M News staff. for the definite cause for definitive treatment. 1998;436:117–126. August 5, 2002. Available at: (http://www.ama- 7. Graudins A, Wilson D, Alewood PF, Broady KW, assn.org/amednews/2002/08/05/hlsa0805.htm). 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