Broader support for my observations
On January 27, 2006, on eMedicine (link is no longer active), dermatologist Adam S. Stibich, MD, published a physiology review of the brown recluse bite. He acknowledged that neutrophils accumulate in the wound at 24 to 72 hours, consistent with the antigen–antibody response postulated in my clinical review. Neutrophils are products of the histamine cascade that most likely brings about tissue necrosis.
Stibich’s plea for conservative management was well founded. He noted that only 10% of envenomation episodes result in large open wounds. The physical findings he described were in keeping with my observation that a subcutaneous necrotic process precedes surface changes.
His treatment of choice was dapsone. He pointed out that other clinicians, too, had reported success with dapsone, and with steroids, antibiotics, hyperbaric oxygen, electric shock therapy, and surgical therapy.3,4,11,12 Stibich commented extensively on these treatment modalities, except electrical shock. However, while the laboratory results achieved were good, clinical outcomes were mixed. Of these treatments, I have experience only with surgery, and I have found that it does not improve the healing process.
Antihistamine and observation: The ideal Tx
The ideal treatment for necrotic wounds from envenomation would account for an underlying antigen–antibody process, shorten the natural history of the illness, result in the least deformity, minimize cost, and allow for errors in diagnosis without harming patients.
The brown recluse gets around
The brown recluse spider is found primarily in the Mississippi River Valley and its tributaries. Its genus members can be found in Arizona, Texas, and South America. They are nocturnal creatures, typically living in woodpiles and secluded dark areas. Usually they are 8 to 9 mm in diameter, but they can reach several centimeters.
Unfortunately, the spider travels well hidden in clothing, so even if you don’t practice medicine in Arizona, Texas, or South America, you could still find yourself treating a patient with a brown recluse spider bite. I saw these wounds in Germany and Spain, on patients who had just arrived from the United States or whose family members had been there. Hite and others have also described this experience.5,12-14
Spider bite or MRSA?
Many people seek care in emergency departments for nasty looking spontaneous abscesses, some of which are in fact spider bites. Increasingly, though, lesions in this setting are colonized with methicillin-resistant Staphylococcus aureus (MRSA). One recent study showed that among patients who visited EDs because of skin infections, more than 58% were infected with MRSA.15 The difficulty is in determining whether MRSA has caused the nasty wound, is a secondary colonization of a spider bite, or if the wound is actually an uninfected spider bite.
Given the simplicity and low cost of antihistamine treatment, I recommend it for wound care in these instances. If the clinical response is good within 24 hours, you are probably dealing with an uninfected spider bite. If the response is slow or the wound worsens after 24 hours, consider adding an antibiotic or performing surgical debridement.
Based on my observations since 1982, I am convinced these necrotic wounds involve an antigen–antibody reaction, are histamine driven, and are adequately treated with oral antihistamines. I now treat presumed necrotic spider bite with antihistamines only. Laboratory or serum testing to confirm a diagnosis has not been useful. It takes too long, costs too much, and does not contribute to management decisions.
If the wound improves dramatically in 24 hours, which is the norm, I continue the antihistamines for 7 to 10 days. If the wound does not improve, I suspect a bacterial component and add an antibiotic. Not once in the last 26 years have I had to resort to surgery.
Correspondence
Paul K. Carlton, Jr, MD, FACS, The Texas A&M University Health Science Center, Office of Homeland Security, 301 Tarrow, 7th Floor, John Connally Building, College Station, TX 77840; carlton@tamhsc.edu