Chief Complaint:
“Spider Bite”
Jill R. Tichy, PGY III
10/2/2009
Spider bites are rare medical events
Typically single lesions
 Do not occur in multiple family members
 Influence of Geographic Location
 Medically significant bites occur:
- Black Widow (Latrodectus mactans)
- Brown Recluse (Loxosceles reclusa)
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Presumptive Diagnosis of Spider Bite
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A spider must be observed inflicting the bite
The spider was recovered, collected, and
properly identified by an expert
entomologist
Brown Recluse
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Dwells in low traffic areas: Attics,
basements and wooodpiles
Brown Recluse
Brown Recluse Bite
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Venom contains Sphingomyelinase B, a
dermonecrotic factor
Initial bite is painless
Within hours site is painful and pruritic with central
induration with zones of ischemia and erythema
Most resolve within a few days
In severe cases erythema spreads and center
lesion becomes necrotic and hemorrhagic
Brown Recluse Bite
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Fevers, chills, weakness, HA,
nausea/vomiting, myalgias, maculopapular
rash, and leukocytosis
Rare complications: Hemolytic Anemia,
DIC, thrombocytopenia, Hemoglobinuria,
Renal Failure
Treatment of Brown Recluse Bite
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Local Cleansing, Cold Compresses,
Analgesics, Anti-histamines, Tetanus
vaccine
Equivocal data for Dapsone within 48-72
hours of bite may halt progression of
necrosis
Black Widow (Latrodectus mactans)
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Webs in dark spaces: barns, under rocks, plants,
garages
Prevalent in southeastern US
Most common in summer to early autumn
Initial bite unnoticed; May have two small fang
marks; No local necrosis
Alpha-latrotoxin binds to nerves and causes
depletion Ach and Norepi
Within 60 minutes of bite, painful cramps ensue
Symptoms can wax and wane for several days
Black Widow Bites
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Unremarkable local lesions
Oftentimes systemic reactions
Proximally spreading pain
Localized diaphoresis
Black Widow Spider Bite
Black Widow Envenomation
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Local pain may be followed by localized or generalized severe muscle cramps and
weakness.
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In severe cases, nause/ vomiting, dizziness and respiratory difficulties may follow.
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Abdominal Pain may mimic a surgical abdomen (peritonitis)
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Chest pain may be mistaken for myocardial infarction
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Labored breathing
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HTN
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Life-threatening reactions are generally seen only in small children and the elderly.
Widow Spider Bite treatment
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Local Wound Care; Ice Packs
Benzodiazepines
Equine Antivenom (Antivenin) reserved
severe cases usually seen in children and
elderly due to high risk of serum sickness
and anaphylaxis
Treatment of Spider bites
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Most cause limited local inflammation: Analgesia
and Antihistamine
Brown Recluse: Standard local wound care and
treat superinfection
Black Widow: IV opiates; Benzodiazepines;
Antivenin if severe reaction in children or elderly
Consider other etiology unless definitive diagnosis
Differential is broad
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Community-acquired methacillin-resistance
Staphylococcus Aureus (CA-MRSA)
Early Lyme Disease: Erythema Migrans
Southern tick-associated rash illness (STARI)
Herpes Zoster and Herpes Simplex (herpetic
whitlow)
Scorpion Bites
Poison Ivy/ Oak
Other insect bites and stings
Cutaneous Lymphoma/Sarcoma
CA-MRSA
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1990s MRSA infections detected in the
community in persons with no contact to
health care system
Strains demonstrate a global, geographic
variation
Small DNA cassettes mediating methacillin
resistance differ from those associated with
hospital acquired strains
CA-MRSA: antibiotic therapy
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No clinical trials for optimal antibiotic therapy
Avoid use of Clindamycin when local rates of
resistance exceed 10-15% among MRSA isolates
causing skin and soft tissue infections
Anecdotal concern for Streptococcus A resistance
to sole therapy of Doxycycline or Bactrim
Possible recurrence rate is > 10%
? Intranasal bactroban “decolonization” efficacy
With increasing prevalence of CAMRSA
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Management of skin and soft tissue
infections requires knowledge of local rates
of MRSA infection
See UNC antibiogram for Community
Isolates for Staphylococcus spp.
Follow-up is essential
UNC antibiogram for community
isolate of Staphylococcus spp; 2008
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All strains: 2216; coag neg: 145; ORSA:
1144; OSSA: 1072
Clindamycin: 66% strain susceptible to
ORSA/ 74 % to OSSA
Doxycycline: 94% susceptible to ORSA
Bactrim: 94% susceptible to ORSA
CA-MRSA
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Abscess +/- Purulent/Necrotic Skin lesion =
I&D
Culture Purulent Material
Lesions < 5cm I&D sufficient
Lesions > 5cm and/or systemic signs of
infection = I&D + Abx
References
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Harrison’s Principals of Internal Medicine; 17th
edition
NEJM; “Skin and Soft-Tissue Infections Caused
by MRSA”; July 26, 2007
Consultant. Vol. 46 No. 12 Necrotic Lesions:
Spider Bite-or Something Else?
Journal of American Board of Family Medicine;
17: 220-226; 2004
UNC Antiobiogram 2008
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