Basics
Description
Local or systemic illness caused by brown recluse spider bite envenomation
Etiology
- Brown recluse spider (also known as the fiddleback spider) features:
- Appearance:
- Delicate body and legs spanning 10 " 25 mm
- Tan- to dark-brown with darker violin-shaped marking visible on the upper aspect of the head
- 3 pairs of eyes
- Found widely throughout the south-central part of US
- Habitat: Typically warm and dry locations, indoors or outdoors such as wood piles, bundles of rags, cellars, under rocks, or in attics
- Bites are typically defensive
- Mechanism of toxicity:
- Venom is a complex cocktail of enzymes and peptides that:
- Binds to RBC and causes hemolysis
- Causes prostaglandin release and activates complement cascade
- Causes lipolysis and tissue necrosis
- Triggers platelet aggregation and thrombosis
- Triggers allergic response to venom antigenic properties
- May lead to shock and DIC in rare cases
- Toxicity proportional to:
- The amount of venom relative to the size of patient
- Location of envenomation on the body
- Children are more vulnerable to a given amount of venom than healthy adults
- Fatality more common in children due to severe intravascular hemolysis
Diagnosis
Signs and Symptoms
Diagnosis is based not only on the clinical presentation but also on a reliable history of a spider bite.
History
- An isolated cutaneous lesion is the most common presentation
- Bite sites are usually located in areas under clothing where spider gets trapped between clothing and skin
- Local wound symptom onset:
- Bite onset is usually asymptomatic, but some may report burning or stinging sensation
- 1 " 24 hr later, patients may report aching or pruritis locally
- Systemic features:
- Rare complication
- More common in children than adults
- Develop during the 1st 1 " 3 days postenvenomation.
- Patient may report:
- Fever, chills
- Weakness, malaise
- Nausea, vomiting, diarrhea
- Dyspnea
- Myalgias, muscle cramps, arthralgias
- Jaundice
- Petechial or urticarial rash
- Generalized pruritic rash
- Hematuria or dark urine
Physical Exam
- Bite wound:
- Usually no visible injury if examined within the 1st 1 " 3 days
- There may be a pinprick lesion, local blanching and induration, or erythema.
- Tissue injury may develop at bite site:
- Initially, bite mark may be surrounded by edema
- Next, an erythematous border will develop around a purple center with a thin ring of ischemia between the 2
- Serous or hemorrhagic bullae may form in the center after 24 " 72 hr
- Blister may gradually enlarge and darken with the development of and eschar of skin and subcutaneous fat necrosis over 3 " 4 days
- Eschar sloughs off 2 " 5 wk later leaving an ulcer in its place
- Necrosis develops most extensively where subcutaneous fat is greatest
- Lower-extremity blisters may spread distally under the influence of gravity
- Local response is not dependent on the extent of envenomation and cannot be used to predict the likelihood or severity of subsequent systemic illness
- Skin:
- Jaundice
- Petechia
- Urticaria
- Generalized maculopapular rash
Essential Workup
- Careful inquiry required to elicit the spider bite history
- Routine lab testing not necessary unless systemic toxicity present.
Diagnosis Tests & Interpretation
Lab
- Spider venom can be detected in skin lesions, but widespread clinical testing is not available yet
- CBC:
- Hemolytic anemia
- Thrombocytopenia, particularly with DIC
- Leukocytosis
- Electrolytes:
- Hyperkalemia or acidosis in renal failure
- BUN, creatinine
- Creatine kinase may be elevated in rhabdomyolysis
- Prothrombin time/partial thromboplastin test may be prolonged in DIC
- d-dimer and fibrin degradation products may be elevated in DIC
- Fibrinogen may be decreased in DIC
- Urinalysis:
- Hemoglobinuria
- Proteinuria
Imaging
- CXR in systemic toxicity
- Soft tissue radiograph of bite site
Differential Diagnosis
- Angioedema
- Bacterial soft tissue infection; MRSA
- Burn
- Cutaneous anthrax
- Diabetic ulcer
- Decubitus ulcer
- Erythema nodosum
- Fungal infection
- Gonococcal hemorrhagic lesion
- Herpes simplex
- IV drug use or "skin popping "
- Vascular insufficiency with secondary ulcer
- Lyme disease
- Neoplastic lesion
- Other arachnid envenomation
- Poison ivy or oak
- Pyoderma gangrenosum
- Sporotrichosis
- Stevens " Johnson syndrome
- Thrombosis
- Vasculitis
- Warfarin use
Treatment
Pre-Hospital
- Loosely immobilize wound site
- Elevate the affected extremity
- Cover bite with cool compresses
- Transport to hospital when patient experiences immediate onset of symptoms
- Supportive measures for patients with systemic symptoms
Every effort should be made by caregivers at the scene to find and bring in the responsible spider for identification.
Initial Stabilization/Therapy
IV fluids, oxygen, cardiac monitoring if the patient is experiencing signs of systemic collapse
Ed Treatment/Procedures
- Cleanse the bite site thoroughly
- Tetanus prophylaxis
- Analgesics
- Antibiotics:
- Appropriate if wound appears infected
- Not indicated prophylactically
- Antistaphylococcal
- Dapsone:
- Controversial: Consider for severe toxicity.
- Screen for G6PD deficiency before initiating
- Monitor for methemoglobinemia, hemolysis, and leukopenia during therapy
- Excision of necrotic wound:
- Not indicated in the 1st 8 wk because may cause more severe ulcer formation
- Hemoglobinuria:
- Treated with IV fluids and alkalinization
- Monitor renal, fluid, and electrolyte status
- Dialysis for renal failure
- Pressors for shock state
- Blood products in severe hemolysis, DIC
- Specific antivenin:
- Not commercially available
- Not FDA approved for use in US
- Therapies requiring further investigation:
- Topical or systemic steroids
- Hyperbaric therapy (has been shown to decrease wound size in animal model)
- Topical nitroglycerin
- Negative pressure wound therapy, or vacuum-assisted closure
Medication
- Antibiotics:
- Clindamycin: 150 " 300 mg PO q6h (peds: 8 " 16 mg/kg/d PO div. QID)
- Severe skin infections:
- Vancomycin: 1 g IVPB q12h (peds: 10 mg/kg q6h)
- Dapsone: Progressive dosage of 50 " 200 mg/d (peds: 2 mg/kg/24 h PO)
- Methylprednisolone: 125 mg IV bolus followed by prednisone 30 " 50 mg/d for 5 days (peds: methylprednisolone 1 " 2 mg/kg IV, prednisone 1 " 2 mg/kg PO)
- Morphine sulfate: 2 " 10 mg (peds: 0.1 mg/kg) IV or IM PRN
- Use dapsone only in severe cases because of increased potential for side effects such as:
- Hepatitis
- Methemoglobinemia
- Hemolytic anemia
- Leukopenia
Follow-Up
Disposition
Admission Criteria
- Significant local reaction or signs of systemic toxicity
- Lower threshold for children, patients with significant comorbidities
Discharge Criteria
- No evidence of systemic toxicity or severe progression of local wound necrosis after envenomation
- Daily reassessment by primary physician, including blood work, until 3 " 4 days after envenomation to evaluate for systemic toxicity
- Patients should be advised about prolonged course for skin healing with consideration for surgical excision after 8 wk
- Patients should be advised about potential for extensive scarring, infection, and recurrent ulceration
Longer observation period or admission because of the higher mortality in this population
Issues for Referral
Consider consultation with:
- General surgery or plastic surgery for wound management
- Hyperbaric specialist for wound management
- Toxicologist
- Nephrologist for cases of renal failure
- Intensivist in cases of shock or DIC
Follow-Up Recommendations
- Primary care physician for continued evaluation of wound
- General surgery or plastic surgery for management of complicated wounds
- Hyperbaric specialist for wound management
Pearls and Pitfalls
- Remember the limited range of brown recluse spiders and the rarity of arachnidism as a cause of necrotic skin wounds
- In the absence of a reliable spider bite by history, other diagnoses must be carefully sought and excluded
- Be sure to screen for G6PD deficiency as it causes methemoglobinemia and hemolysis in patients receiving dapsone
- Have a low threshold for admitting pediatric patients, adults with systemic symptoms, or anyone with a large, painful, or infected wound
Additional Reading
- Furbee RB, Kao LW, Ibrahim D. Brown recluse spider envenomation. Clin Lab Med. 2006;26(1):211 " 226.
- Mold JW, Thompson DM. Management of brown recluse spider bites in primary care. J Am Board Fam Pract. 2004;17:347 " 352.
- Swanson DL, Vetter RS. Bites of brown recluse spiders and suspected necrotic arachnidism. N Eng J Med. 2005;352:700 " 707.
- Wong SC, Defranzo AJ, Morykwas MJ, et al. Loxoscelism and negative pressure wound therapy (vacuum-assisted closure): A clinical case series. Am Surg. 2009;75(11):1128 " 1131.
See Also (Topic, Algorithm, Electronic Media Element)
Spider Bite, Black Widow
Codes
ICD9
989.5 Toxic effect of venom
ICD10
T63.331A Toxic effect of venom of brown recluse spider, acc, init
SNOMED
- 40119006 poisoning due to brown recluse spider venom (disorder)