Table of contents
Expand All Topics
Spider envenomation
Background
Overview
Definition
Spider bites in the US are primarily caused by widow spider (Latrodectus) and brown recluse spider (Loxosceles). Less common spiders include Australian funnel web spiders (Atrax and Hadronyche species) found in eastern Australia, armed or wandering spiders (Phoneutria species) found in South America, hobo spiders (Tegenaria agrestis) found in Europe and in the Pacific Northwest of the US, and the noble false widow (Steatoda nobilis) found in England and Ireland.
1
Pathophysiology
The venom of the widow spide contains α-latrotoxin, which affects the neuromuscular junction, leading to muscle cramping and hypertension. The venom of the brown recluse spider contains multiple active components, including sphingomyelinase D hyaluronidase, and other enzymes, resulting in local tissue necrosis and, rarely, systemic effects.
2
Epidemiology
There were 142,886 spider bites treated in emergency departments in the US from 2001 to 2010.
3
Disease course
Most spider bites cause only localized skin injury, such as burning pain, swelling, erythema, and bleeding, typically on the upper oextremities. Fang marks and a hemorrhagic vesicle may also be observed. Skin necrosis may develop by 72 hours. Systemic symptoms include fever, chills, headache, nausea and vomiting, diarrhea, pruritus, malaise, and musculoskeletal pain. Systemic toxicity leading to intravascular hemolytic anemia, coagulopathy, and acute renal failure is rare.
1
Prognosis and risk of recurrence
Most spider bites are mild and resolve with supportive care. Systemic toxicity and mortality are rare.
1
Guidelines
Key sources
The following summarized guidelines for the management of spider envenomation are prepared by our editorial team based on guidelines from the American Red Cross (ARC/AHA 2024) and the American Academy of Family Physicians (AAFP 2022).
1
2
3
4
Medical management
Management of widow spider envenomation: as per AAFP 2022 guidelines, manage widow spider envenomations supportively with analgesics and benzodiazepines for muscle spasm, reserving antivenom for severe cases with refractory symptoms.
B
More topics in this section
Management of brown recluse spider envenomation
Patient education
Education on first aid: as per AHA/ARC 2024 guidelines, educate patients on the following:
call emergency services if a person bitten by a spider develops symptoms throughout the body, such as difficulty breathing, muscle rigidity, dizziness, or confusion
seek medical care if pain from a spider bite extends beyond the site of the bite/sting, becomes severe, and is not controlled by OTC pain medications; if an open wound develops; or if the person experiences symptoms throughout the body.
B