Spider

What is this pictured spider that can inflict a deadly bite?

  1. Black Widow Spider (Latrodectus mactans)
  2. Brown Recluse Spider (Loxosceles reclusa)
  3. Redback Spider (Latrodectus hasselti)
  4. Sydney Funnel Web Spider (Atrax robustus)

[Image from thebeachcomber, CC BY 4.0 https://creativecommons.org/licenses/by/4.0, via Wikimedia]

4. Sydney Funnel Web Spider (Atrax robustus)

Background [1-3]

The Sydney funnel web spider is geographically distributed in eastern Australia near populated areas, and most activity occurs within the summer months when males are searching for mates. When disturbed, the Sydney funnel web spider can inject deadly venom which has been associated with fourteen reported fatalities. They burrow in moist, cool, sheltered habitats and build a funnel-shaped web.

What are the symptoms of a Sydney funnel web spider bite? [3-5]

  • Nausea and vomiting
  • Salivation
  • Diaphoresis
  • Facial paresthesia
  • Muscle fasciculations and cramping
  • Autonomic instability: Tachycardia or bradycardia, hypertension or hypotension
  • Pulmonary edema
  • Cerebral Edema
  • Deaths can occur within 15 minutes, particularly in small children.

What is the toxin in Sydney funnel web spider venom? [3-7]

  • Venom from male spiders contains d-Atracotoxin-Ar1 (also known as robustoxin) which slows and inactivates voltage-gated sodium channels.
  • The venom is thought to have developed during evolution for defense against larger predators.
  • After envenomation, symptoms typically occur within minutes, and rarely beyond two hours.
  • Fortunately, only 10-15% of bites are estimated to be venomous.

How do you treat a Sydney funnel-web spider bite? [3,4,8-10]

  • Cleanse the bite site with soap and water.
  • Field immobilization and a pressure wrap are recommended within 4 hours post-bite to delay symptom onset until the patient arrives at a medical facility.
  • Patients should be monitored for 4-6 hours post envenomation for the development of systemic effects, and at least 2 hours after removal of immobilization bandages.
  • Funnel Web Spider Antivenom (FWSAV), introduced in 1981, has been associated with symptom resolution and decreased mortality.
  • FWSAV is indicated for signs of systemic toxicity.
    • Initial dose: 2 vials intravenously
    • Repeat dosing: 2 vials intravenously after 15 minutes if required.
    • Most patients only require 2 vials
    • Patients rarely require more than 4 vials in total.
  • In Australia, the universal number for the Poisons Information Centre is 13 11 26.

Bedside Pearls

  • In an endemic area, funnel web spider envenomation can be deadly.
  • Immobilization and a pressure bandage are recommended in the field.
  • Monitor for at least 4-6 hours post envenomation.
  • Administer Funnel Web Spider Antivenom in patients with systemic toxicity.
  • In Australia, contact the Poisons Information Centre at 13 11 26 for management advice.

References

  1. The Australian Museum. Funnel-web Spiders. October 11, 2023.  Accessed May 23, 2024.
  2. Fletcher JI, Chapman BE, Mackay JP et al. The structure of versutoxin (delta-atracotoxin-Hv1) provides insights into the binding of site 3 neurotoxins to the voltage-gated sodium channel. Structure. 1997 Nov 15;5(11):1525-35. PMID: 9384567.
  3. Funnel Web Spider Guideline. Toxicology and Toxinology Handbook. Version 3 (2020). Therapeutic Guidelines. Victoria, Australia.
  4. Binstead JT, Chen RJ, Nappe TM. (2024) Funnel-Web Spider Toxicity. 2024 Feb 26. In: StatPearls. Treasure Island (FL): StatPearls Publishing. PMID: 30571015.
  5. Sheumack DD, Claassens R, Whiteley NM, Howden ME. Complete amino acid sequence of a new type of lethal neurotoxin from the venom of the funnel-web spider Atrax robustus. FEBS Lett. 1985;181(1):154-6. PMID: 3972101.
  6. Nicholson GM, Little MJ, Birinyi-Strachan LC. Structure and function of δ-atracotoxins: lethal neurotoxins targeting the voltage-gated sodium channel. Toxicon 2004; 43: 587-599. PMID:15066415.
  7. Herzig V, Sunagar K, Wilson DTR et al. Australian funnel-web spiders evolved human-lethal δ-hexatoxins for defense against vertebrate predators. Proc Natl Acad Sci USA. 2020 Oct 6;117(40):24920-24928. PMID: 32958636.
  8. Sutherland SK, Duncan AW, Tibballs J. Local inactivation of funnel-web spider (Atrax robustus) venom by first-aid measures: potentially lifesaving part of treatment. Med J Aust. 1980;2(8):435-7. PMID: 7207322.
  9. Isbister GK, Gray MR, Balit CR et al. Funnel-web spider bite: a systematic review of recorded clinical cases. Med J Aust. 2005;182(8):407-11. PMID: 15850438.
  10. 10.Sequirus Pty Ltd.  Product Information: Funnel Web Spider Antivenom (AUST R 31847). August 20, 2019. Accessed May 23, 2024.
Doug Maslowski MD

Doug Maslowski MD

Emergency Medicine Resident
Department of Emergency Medicine
Carolinas Medical Center
Doug Maslowski MD

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Anna Dulaney, PharmD, DABAT

Anna Dulaney, PharmD, DABAT

Clinical Toxicologist
Division of Medical Toxicology
Department of Emergency Medicine
Atrium Health’s Carolinas Medical Center
Anna Dulaney, PharmD, DABAT

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