Felis ISSN 2398-2950

Spider bites

Synonym(s): Arachnism; Latrodectism (for Black Widow or Redback; Loxoscelism (for Brown Recluse; Necrotic arachnism (Loxoscelism and others

Contributor(s): Rosalind Dalefield, Dawn Ruben

Introduction

  • Venomous spiders are found in many countries including the USA and Australia.
  • Spider bites are considered rare but may be fatal, especially if multiple.

Pathogenesis

Etiology

  • Envenomation by means of a spider bite.

Predisposing factors

General

  • With the exception of the Sydney Funnel-Web spider, which is aggressive, most spiders bite in self-defense and will seek to escape rather than to bite.  Bites tend to occur when people or animals inadvertently sit or lie on a spider. Latrodectus spiders are most aggressive when guarding an egg sac.

Pathophysiology

  • Latrodectus venom contains (a-Latrotoxin, a potent neurotoxin, and other toxins. The toxins are believed to bind to calcium channels, enhancing depolarization. Epinephrine Epinephrine and norepinephrine release is increased and presynaptic reuptake inhibited.
  • Loxosceles venom contains a number of proteins including hyaluronidase, proteases, and hemolysins.  The venom damages endothelia, and promotes intravascular coagulation and tissue necrosis.

Timecourse

  • Latrodectism: Clinical signs become apparent very shortly (10 to 60 minutes) after the bite, and progress rapidly.
  • Loxoscelism: The initial bite is often not noticed and the lesion takes a few days to develop.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

Other sources of information

  • Osweiler G D Toxicology, Williams and Wilkins 1996.
  • Fowler M E Veterinary Zootoxicology, CRC Press 1993.
  • Little P Spider Envenomation in Dogs and Cats. Clinical Toxicology, Proceedings 318, Post Graduate foundation in Veterinary science, University of Sydney, 1998.

Organisation(s)


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