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)
Presumptive Diagnosis of Spider Bite
A spider must be observed inflicting the bite The spider was recovered, collected, and
properly identified by an expert entomologist
Brown Recluse Dwells in low traffic areas: Attics,
basements and wooodpiles
Brown Recluse
Brown Recluse Bite 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 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 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) 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 Unremarkable local lesions Oftentimes systemic reactions Proximally spreading pain Localized diaphoresis
Black Widow Spider Bite
Black Widow Envenomation Local pain may be followed by localized or generalized severe muscle cramps and
weakness.
In severe cases, nause/ vomiting, dizziness and respiratory difficulties may follow.
Abdominal Pain may mimic a surgical abdomen (peritonitis)
Chest pain may be mistaken for myocardial infarction
Labored breathing
HTN
Life-threatening reactions are generally seen only in small children and the elderly.
Widow Spider Bite treatment 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 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 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 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 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 CA-MRSA
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
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 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 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 Uptodate.com