chief complaint: “spider bite” jill r. tichy, pgy iii 10/2/2009

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