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Brown Recluse Spider

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Poisonous to: Cats, Dogs

Level of toxicity: Generally moderate to severe

Common signs to watch for:

  • Vomiting
  • Fever
  • Lethargy
  • Bleeding disorders (e.g., bruising, abnormal clotting tests)
  • Organ damage (e.g., liver, kidneys)
  • Severe skin wounds
  • Death

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The brown recluse spider (Loxosceles reclusa) is found throughout the southern Midwest region of the United States. It can also be found less commonly in the southwestern states. This spider, which ranges from 8-13 mm in length, has long legs (20-30 mm in length), and ranges in shades of brown. It has a violin shape on the dorsal cephalothorax. The venom in the brown recluse spider is a mix of phospholipases and proteases (e.g., sphingomyelinase D), which results in severe clinical signs. However, there is tremendous variability of the strength of the venom. Animals bitten by a brown recluse spider may show clinical signs of vomiting, fever, lethargy, bleeding disorders (e.g., bruising, abnormal clotting tests), organ damage (e.g., liver, kidneys), and severe skin wounds. Unfortunately, no antivenom is available for this specific spider, and treatment is symptomatic and supportive.

If you think your dog or cat were bitten by a brown recluse spider, call your veterinarian or Pet Poison Helpline immediately for life-saving treatment advice.

Poison type: Envenomations

Alternate names: Loxosceles, spider, sphingomyelinase D, venom