Funnel-web spider bite

Background[1]

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

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

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

External Links

References

  1. Leslie V. Boyer, Greta J. Binford, Janice A. Degan. Spider Bites. Paul S. Auerbach. In: Auerbach’s Wilderness Medicine. 7th Ed. 2017: 1002-1003.