spider bite
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Epidemiology
- report of spider bite in the setting of soft tissue infection suggests MRSA
- ~3 deaths/year in U.S, due to spider bites, mostly in children[4]
Clinical manifestations
- normal reaction following any sting or bite
- immediate local pain with swelling
- subsides within 1-2 hours
- pruritus that may persist for days
- dermonecrotic reaction
- brown recluse spider (Loxoscele reclusa) bite is prototypic
- bite may go unnoticed
- papule at site with pain & tenderness 24-72 hours after bite
- later, hemorrhagic blister surrounded by irregular purpura
- necrotic ulcer develops later & may take weeks to heal
- toxic systemic reaction
- most commonly due to neurotoxins of arthropod venom
- systemic loxoscelism (bite of brown recluse spider)
- symptoms start 24-72 hours after bite
- fever, malaise, rash, arthralgias, nausea/vomiting
- splenomegaly
- lactrodectism (bite of black widow spider)
- bite often unnoticed or victim may notice pinprick sensation
- onset of symptoms in 20-30 minutes
- limb & lymph node swelling
- local swelling, itching & hives
- may progress to cramps in thighs, abdomen & chest, sialorrhea, nausea/vomiting
- hypertension
- muscle rigidity
* images of brown recluse spiders & black widow spiders & their bites[3]
Laboratory
- complete blood count (CBC) & chem 7
- leukocytosis & hyperglycemia typical of stress reaction
- generally laboratory tests not useful
- severe reactions
- elevated serum creatine kinase
- abnormal renal function tests
- abnormal coagulation studies
- activated partial thromboplastin time (aPTT)
- increased D-dimer
- specific tests for brown recluse spider bite
- enzyme immunossay on skin biopsys or plucked hairs
- passive hemagglutination inhibition test
- up to 3 days after envenomation[2]
Complications
- purulent soft tissue infection due to MRSA[1]
Differential diagnosis
- most spider bites are misdiagnosed folliculitis or furuncles[2]
- local reaction
- dermonecrotic reaction
- systemic reaction
Management
- local reactions
- cool compresses
- topical lotions
- secondary infection treated as cellulitis with antibiotics
- antihistamines
- chlorpheniramine 4-8 mg every 6 hours
- diphenhydramine 50 mg PO every 6 hours
- prednisone 40 mg PO QD for 2-3 days
- dermonecrotic reactions
- immobilize limb
- apply cold compresses
- Sawyer extractor (extracts venom with negative pressure)
- tetanus prophylaxis
- antibiotics for secondary infection
- dapsone for adults with rapidly progressive reaction; 50-500 mg QD divided BID for 2 weeks
- colchicine 1.2 mg initially, then 0.6 mg every 2 hours for 2 days, then 0.6 mg every 4 hours for 2 days
- delay corrective surgery for 8 weeks to allow adequate tissue demarcation of necrosis
- systemic reaction
- supportive care
- ABC's of resuscitation (airway, breathing, circulation)
- intravenous volume expansion
- monitoring
- oxygen
- brown reclusive spider bite
- black widow spider bite
- muscle relaxants to provide symptomatic relief
- diazepam
- methocarbamol 15 mg/kg IV, followed by oral therapy
- calcium gluconate 10%, 1-2 mg/kg up to 10 mL/dose provides transient relief
- antivenin available from Merck & Co (West Point, PA
- muscle relaxants to provide symptomatic relief
- supportive care
- associated soft tissue infection
- consider treatment with clindamycin or Bactrim for MRSA
More general terms
More specific terms
Additional terms
References
- ↑ 1.0 1.1 Saunders Manual of Medical Practice, Rakel (ed), WB Saunders, Philadelphia, 1996, pg 1172-74
- ↑ 2.0 2.1 2.2 2.3 Medical Knowledge Self Assessment Program (MKSAP) 15, 16, 17, 18. American College of Physicians, Philadelphia 2009, 2012, 2015, 2018.
- ↑ 3.0 3.1 emedicinehealth (images) Brown Recluse Spider Bite http://www.emedicinehealth.com/spider_bite_brown_recluse_spider_bite/article_em.htm
- ↑ 4.0 4.1 Grimm L Medically Significant Spider Bites: Which to Watch Out For, Medscape. July 25, 2023 https://reference.medscape.com/slideshow/venomous-spiders-31606