Introduction
Background
The brown recluse spider (Loxosceles reclusa; see Media Files 1-2) is the most prevalent of the Loxosceles species in the United States. All Loxosceles species have the potential to inflict injury to varying degrees. Seen predominantly in the south central part of the United States, the brown recluse spider has been discovered as far north as Illinois and on both coasts. Other members of the Loxosceles species are found throughout the world.
Brown recluse spider. Courtesy of US Centers for Disease Control and Prevention.
Brown recluse spider. Courtesy of US Centers for Disease Control and Prevention.
Incidents involving the brown recluse spider usually occur in summer months as a consequence of the spider's activity patterns. Bites are rare, even in houses heavily infested with brown recluse spiders; therefore, a diagnosis of brown recluse spider bite is quite unlikely in areas that lack significant populations of Loxosceles spiders.
Bites of the brown recluse spider can cause a condition termed necrotic arachnidism, which begins with the development of an eschar at the bite site, followed by tissue necrosis and skin sloughing. Several groups of spiders have been linked to necrotic skin lesions, but recluse spiders cause most of these lesions. While most recluse bites heal uneventfully, some have a protracted course, with the wound taking months to resolve completely.
The brown recluse spider commonly is known as the fiddle-back or violin spider because of the distinguishing mark on its cephalothorax. The dull yellow-to-brown coloring of its body further distinguishes the brown recluse. It has a small body relative to its leg span, and 3 pairs of eyes rather than the 4 pairs typical of other spiders. The reclusive mannerism is demonstrated by the locations in which the spiders are encountered. They prefer dark, dry, and undisturbed locations, such as the undersides of logs, boards, and rocks and inside barns and garages. Genital bites have been seen on patients using outhouses. Within homes they are found in attics, closets, and storage areas for bedding, clothing, and furniture. Both the male and female spider can envenomate.
In 2008, Vetter and Rust1 reported on the refugia preferences of the brown recluse spider. In this study, brown recluse spiders were offered a variety of refugia in order to determine whether they preferred certain types of refugia spaces. Observations revealed that some individual spiders always preferred the same refugium for the entire study period; other individuals changed refugia every 2-3 d. The degree of starvation over the period tested did not affect the propensity to switch refugia. This type of research may aid in the development of novel control measures for Loxosceles spiders.
Other eMedicine articles from different specialty perspectives include Spider Envenomation, Brown Recluse (emergency medicine) and Spider Bites (ophthalmology).
Pathophysiology
Bites and envenomation range from a mild, local, urticarial reaction to full-thickness necrosis.
The venom volume is minute, about 4 µL, with 65-100 mcg of protein. The venom contains alkaline phosphatase, 5'ribonucleotide phosphohydrolase, esterase, lipase, hyaluronidase, and, most importantly, sphingomyelinase D2. Sphingomyelinase D2 is responsible for calcium-dependent direct erythrocyte lysis. The degree of hemolysis is individually variable from 20% to more than 95%.
Cutaneous necrosis is completely dependent on activation of neutrophils. In rabbit studies, neutrophil infiltration occurs at 6 hours. Neutrophils significantly accumulate at 24-72 hours, preceding skin necrosis and ulceration. This explains why early dapsone initiation may be important to limit necrosis in bites destined for that reaction.
Frequency
United States
In 1994, 1835 brown recluse spider bites were reported to poison control centers nationwide. In South Carolina alone, physicians diagnosed 478 brown recluse spider bites in 1990 and 738 in 2004.2 However, the number of brown recluse spider bites reportedly diagnosed in South Carolina greatly outnumbers the verified brown recluse specimens that have been collected in the state, a pattern of bite diagnoses outnumbering verified brown recluse specimens noted in other areas outside of this spider's known endemic range. The veracity of publications reporting skin disease caused by the brown recluse spider, L reclusa, has been questioned by others too, as many of these articles contain inadequate documentation of Loxosceles bites.3,4,5 The same has been postulated in the US state of Georgia.6 Bite diagnoses should be made with caution.
International
The incidence of bites and envenomation is unknown.
Mortality/Morbidity
- Death is uncommon. Most patient occurrences documented with fatal envenomation have involved hematologic disorders in children.
- Systemic loxoscelism is unusual, especially in adults. Cutaneous loxoscelism is not uncommon with bites. Few envenomations, perhaps less than 10%, result in severe skin necrosis or other systemic manifestations.
Age
Systemic loxoscelism is most common in children.7
Clinical
History
- Constitutional symptoms, including a macular, papular, urticarial, vasculitic, petechial, scarlatiniform, or morbilliform eruption: The brown recluse spider bite may appear as generalized exanthem, show localized necrosis, and, rarely, have potentially lethal systemic involvement.8
- Hematologic disorders, such as hemolysis,9 hemoglobinuria, thrombocytopenia, disseminated intravascular coagulation, methemoglobinemia, and shock (rare but serious complications)
- Fever
- Headache
- Malaise
- Arthralgia and rhabdomyolysis
- Nausea
- Vomiting
- Renal failure
Physical
The bite typically is painless, and findings of a central papule and associated erythema may not be seen for 6-12 hours. Few envenomations, perhaps less than 10%, result in severe skin necrosis or other systemic manifestations.
- Wounds destined for necrosis usually show signs of progression within 48-72 hours of the bite.
- Central blistering with a surrounding gray-to-purple discoloration of the skin may be seen at the bite site.
- A surrounding ring of blanched skin is itself surrounded by a large area of asymmetric erythema leading to the typical "red, white, and blue" sign of a brown recluse bite. At this stage of evolution, these bites may be associated with significant pain related to incipient necrosis of skin and subcutaneous tissues. The resultant eschar and ulceration may take months to resolve.
Within an hour, the bite area swelled to the size of a quarter. The area turned blue and dark red by the evening of the first day, exceeding the boundaries of a circle drawn around the area of initial swelling by the patient's physician. Courtesy of Dale Losher.
- Note that patients who are destined for a severe reaction usually develop key signs within 6-12 hours, such as bullae formation, cyanosis, and hyperesthesia.
- Areas with increased adipose tissue, such as the thighs, buttocks, and abdomen, are more likely to undergo severe necrosis than bites occurring at other sites.
The third day after the bite. The skin continues to die. Courtesy of Dale Losher.
Another view of the wound 3 days after the bite. Courtesy of Dale Losher.
Nine days after the bite. The patient endured 8 days with an open wound to drain the spider's toxins and needed intravenous antibiotics and pain medication almost 24 h/d. Courtesy of Dale Losher.
Eleven days after the bite. A 5-inch wide area of dead tissue was excised, necessitating skin grafting. Courtesy of Dale Losher.
Brown recluse spider bite. Waiting to see skin graft results 38 days after the bite. Courtesy of Dale Losher.
Skin graft results 38 days after the bite. Courtesy of Dale Losher.
View of healed wound approximately 10 months after bite. Courtesy of Dale Losher.
More on Brown Recluse Spider Bite |
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| Differential Diagnoses & Workup: Brown Recluse Spider Bite |
| Treatment & Medication: Brown Recluse Spider Bite |
| Follow-up: Brown Recluse Spider Bite |
| Multimedia: Brown Recluse Spider Bite |
| References |
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Further Reading
Keywords
brown recluse spider bite, brown recluse spider, spider bite, Loxosceles reclusa, L reclusa, Loxosceles species, insect bite, arachnid, arachnid bite, necrotic arachnidism, necrotic skin lesions, fiddle-back spider, violin spider
