Funnel-web spider bite

Background

Female Blue Mountains Funnel-web Spider, (Hadronyche versuta) Image: Mike Gray

• Identification: Glossy black cephalothorax and velvety black abdomen, often with reddish hairs.
  • Females grow up to 4cm in length, whereas males are smaller and more delicate.
  • Females dig a funnel shaped burrow under rocks, logs or building foundation and rarely stray, whereas males wander after reaching maturity and may enter buildings
  • Aggressive behavior, 4-5mm fangs which can penetrate a chicken skull, and potent venom make these among the deadliest spiders in the world.
• Genus: Atrax and Hadronyche
• The most clinically relevant species are restricted to Eastern Australia near Sydney and the central coast region of New South Wales and adjacent Blue Mountains.

Venom

• Components of the venom include Atraxotoxin and Robustoxin which appear to induce widespread neurotransmitter release, resulting in neuromuscular and autonomic stimulation.

Clinical Features

• 90% of bites will not involve significant envenomation.
• Local Symptoms:
  • Intense pain, wheal with erythema at injection site, localized sweating with piloerection,
  • Lasts for 30min
  • Is not thought to produce skin necrosis
• Systemic Symptoms
  • Earliest: Perioral tingling, diaphoresis, nausea/vomiting, salivation, and lacrimation.
  • Severe:
    • Pulmonary edema with dyspnea
    • Peripheral neuromuscular syndrome including fasciculations, tremors, and spasms
    • Impaired consciousness
    • Death due to pulmonary edema, hypotension, or cardiac arrest

Differential Diagnosis

Envenomations, bites and stings

• Hymenoptera stings (bees, wasps, ants)
• Mammalian bites
  • Closed fist infection (Fight bite)
  • Dog bite
• Marine toxins and envenomations
  • Toxins (ciguatera, neurotoxic shellfish poisoning, paralytic shellfish poisoning, scombroid, tetrodotoxin
  • Stingers (stingray injury)
  • Venomous fish (catfish, zebrafish, scorpion fish, stonefish, cone shells, lionfish, sea urchins)
  • Nematocysts (coral reef, fire coral, box jellyfish, sea wasp, portuguese man-of-war, sea anemones)
  • Phylum porifera (sponges)
  • Bites (alligator/crocodile, octopus, shark)
• Scorpion envenomation
• Reptile envenomation
  • Snake bites
    • Crotaline (Pit Vipers)
    • Elapidae (Coral Snakes)
  • Lizard bites
• Spider bites
  • Black widow
  • Brown recluse
  • Tarantula
  • Funnel-web spider bite
  • Armed spider bite

Evaluation

• Generally a clinical diagnosis

Management

• Pressure Immobilization Dressing
  • Wrap the length of the bitten extremity with an elastic bandage
  • Splint the extremity in neutral position to immobilize
  • Immobilize victim and transport to medical care
  • If a patient presents with a tourniquet or pressure immobilization dressing, obtain IV access for potential resuscitation before removing.
• Supportive Care
  • O2, mechanical ventilation if needed
  • Gentle IV fluids
  • Atropine for sialorrhea bronchorrhea
• Antivenom
  • Specific IgG antivenom has been developed by Commonwealth Serum Laboratories
  • Empiric treatment with 2 amps (100mg/amp) of IgG in the setting of systemic signs/symptoms
  • 2amps repeated Q15 min until symptom resolution occurs
  • 2-8amps total dose reported
  • No difference in dosing between adults and peds.
  • No adverse effects reported in 40 patients over 10 years

Disposition

• May discharge those without systemic signs after period of ED observation
• Admit those with systemic signs or requiring antivenom

See Also

• Spider bites