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spider bite

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: 1) normal reaction following any sting or bite a) immediate local pain with swelling b) subsides within 1-2 hours c) pruritus that may persist for days 2) dermonecrotic reaction a) brown recluse spider (Loxoscele reclusa) bite is prototypic b) bite may go unnoticed c) papule at site with pain & tenderness 24-72 hours after bite d) later, hemorrhagic blister surrounded by irregular purpura e) necrotic ulcer develops later & may take weeks to heal 3) toxic systemic reaction a) most commonly due to neurotoxins of arthropod venom b) systemic loxoscelism (bite of brown recluse spider) 1] symptoms start 24-72 hours after bite 2] fever, malaise, rash, arthralgias, nausea/vomiting 3] splenomegaly c) lactrodectism (bite of black widow spider) 1] bite often unnoticed or victim may notice pinprick sensation 2] onset of symptoms in 20-30 minutes 3] limb & lymph node swelling 4] local swelling, itching & hives 5] may progress to cramps in thighs, abdomen & chest, sialorrhea, nausea/vomiting 6] hypertension 7] muscle rigidity * images of brown recluse spiders & black widow spiders & their bites [3] Laboratory: 1) complete blood count (CBC) & chem 7 - leukocytosis & hyperglycemia typical of stress reaction 2) generally laboratory tests not useful 3) severe reactions a) elevated serum creatine kinase b) abnormal renal function tests 1] serum urea nitrogen 2] serum creatinine c) abnormal coagulation studies 1] prothrombin time (PT) 2) activated partial thromboplastin time (aPTT) 3) increased D-dimer 4) specific tests for brown recluse spider bite a) enzyme immunossay on skin biopsys or plucked hairs b) passive hemagglutination inhibition test c) up to 3 days after envenomation [2] Differential diagnosis: 1) most spider bites are misdiagnosed folliculitis or furuncles [2] 2) local reaction - atopic dermatitis - allergic or contact dermatitis - viral infection - drug eruption 3) dermonecrotic reaction - vasculitis - pyoderma, pyoderma gangrenosum - Lyme disease - MRSA skin infection [2] 4) systemic reaction - secondary syphilis - acute psychosis - meningitis - acute renal failure Complications: - purulent soft tissue infection due to MRSA [1] Management: 1) local reactions a) cool compresses b) topical lotions - calamine - camphor-menthol c) secondary infection treated as cellulitis with antibiotics d) antihistamines - chlorpheniramine 4-8 mg every 6 hours - diphenhydramine 50 mg PO every 6 hours e) prednisone 40 mg PO QD for 2-3 days 2) 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 3) systemic reaction a) supportive care - ABC's of resuscitation (airway, breathing, circulation) - intravenous volume expansion - monitoring - oxygen b) brown reclusive spider bite - treat acute renal failure - treat disseminated intravascular coagulation c) black widow spider bite - muscle relaxants to provide symptomatic relief - diazepam - 5-10 mg IM/IV every 3-4 hours - children 1 month-5 years 1-2 mg/dose, larger doses for severe spasm - 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 4) associated soft tissue infection - consider treatment with clindamycin or Bactrim for MRSA

Related

hymenoptera (insect) sting insect bite lactrodectism loxoscelism tick bite

Specific

black widow spider envenomation

General

animal bite superficial injury/trauma

References

  1. Saunders Manual of Medical Practice, Rakel (ed), WB Saunders, Philadelphia, 1996, pg 1172-74
  2. Medical Knowledge Self Assessment Program (MKSAP) 15, 16, 17, 18. American College of Physicians, Philadelphia 2009, 2012, 2015, 2018.
  3. emedicinehealth (images) Brown Recluse Spider Bite http://www.emedicinehealth.com/spider_bite_brown_recluse_spider_bite/article_em.htm
  4. Grimm L Medically Significant Spider Bites: Which to Watch Out For, Medscape. July 25, 2023 https://reference.medscape.com/slideshow/venomous-spiders-31606