The Brown Recluse Spider
Its Bite is Worse than Its Bark (under which it lives)
Charles D. Ponte, PharmD, BC-ADM, BCPS, CDE, FAPhA, FASHP, FCCP
Professor of Clinical Pharmacy and Family Medicine
Robert C. Byrd Health Sciences Center
West Virginia University
Schools of Pharmacy and Medicine
Morgantown, West Virginia
During the spring, summer and early fall months, our thoughts turn to spending time outdoors doing a myriad of recreational activities. Our preoccupation with fun-seeking and chasing the sun, leaves us little time to contemplate the dangers that may lurk under our picnic table, on our favorite hammock or under the seat of an outdoor toilet. During the winter months, indoor activities predominate. Yet, these same dangers may lurk in the dark hidden recesses of the basement, garage or attic. Every year, tens of thousands of individuals are bitten or suffer from envenomation from insects, reptiles, mammals, snakes and spiders. According to the 2004 report of the American Association of Poison Control Centers Toxic Exposure Surveilllance System (TESS), overall there were approximately 97,000 bites and envenomations with over 2800 cases resulting from the Brown recluse spider. (Watson et al 2005) Persons with suspected bites may seek consultation with a primary care provider for proper treatment recommendations and triage. Therefore, it is imperative that family physicians have a working knowledge of the Brown Recluse spider, its habitat, the potential consequences of envenomation and contemporary management principles. This article will briefly describe these issues for the reader.
Characteristics and Distribution
The Brown Recluse spider is indigenous to the United States and is geographically located primarily in the south central portions of the country but its distribution is growing to include most of the southern half of the United States.
The spider (Loxosceles reclusa) is also commonly known as the “fiddleback” or “violin” spider. As these common names imply, the markings on the back of the spider (cephalothorax) look like a violin with the neck pointing toward the back (or abdomen) of the spider. This characteristic marking is not present in all spiders and may be absent in the young and following molting. Its color varies from light tan to dark brown. The spider itself can range in color from uniformly brown to deep yellow. These spiders are rather small with sizes ranging from 1/4 to 3/4 inches. Males and females are approximately the same size. With legs extended, the spider can occupy the size of a quarter. Unlike most spiders, the Brown Recluse spider has only six eyes instead of eight. The eyes are arranged in three pairs about the head and are best seen with a low power magnifying glass. The spider is not hairy nor is its legs spiny in appearance.
The Brown Recluse spider lives both indoors and outdoors. It can be found indoors in virtually any dark secluded area such as the basement, attic, closets and even the garage. The spiders can be found in bedding, shoes and hiding within or among cardboard boxes. Outdoors they can be found in woodpiles, beneath rocks, fallen trees, tree stumps, picnic furniture and even outdoor toilets and abandoned tires. Unlike the females, male spiders are more adventuresome and will travel away from their web.
Generally, the Brown Recluse spider is docile and non-aggressive. Human bites typically occur when the spider is threatened, injured or when it is pressed against the skin (e.g., putting on a shoe or other clothing, placing a hand in an unsuspected place or sitting on an outdoor toilet). Bites typically involve the extremities (including the thigh and lateral torso) are self-limited and non-life threatening. (Furbee RB et al, 2006 and Hogan CJ et al, 2004) Bites on the face, neck, hands and feet are uncommon. (Furbee RB et al, 2006) Of interest, most bites occur in persons over the age of 19 and are unintentional.(Watson et al 2005)
The severity of the bite reaction will depend upon the amount of venom injected as well as host factors. (Jones SC, 2004) The very young, older adults and immunosupressed individuals may be particularly vulnerable to the systemic effects of envenomation. Some persons may not realize that they had been bitten until cutaneous or more rarely, systemic manifestations occur. Within a few hours of envenomation, the bite site develops a typical inflammatory reaction, although severe burning pain is common and is consistent with a Loxosceles bite. During the early stages of envenomation, a hemorrhagic eruption may occur (there may be a whitish ring around the lesion) or a whitish blister develops circled by typical erythematous changes. Eventually, a blue-white or blue-grey “raggedy” ulcer forms and the resulting eschar sinks into the adjacent inflamed skin. This evolution seen at the site of envenomation has been referred to as the “red, white and blue sign”. (Hogan CJ, 2004 and Jones SC, 2004) Deep ulcers may require weeks to months to heal and are often associated with scarring. Large areas of devitalized tissue from serious bite wounds may require debridement and plastic surgery to correct the cosmetic defects.
A definitive diagnosis of a Brown Recluse spider bite cannot be made via the clinical presentation alone. If captured or killed, the spider should be identified by a qualified professional who is able to identify unique characteristics of this arachnid. Likewise, a thorough history from the victim will assist the clinician in making a more accurate assessment.(Vetter RS and Bush SP, 2004) The differential diagnosis of ulcerated skin lesions is long and includes such entities as insect bites, Staphylococcal and Streptococcal cellulitis, decubitus ulcers, vascular insufficiency and drug eruptions. Therefore, it is incumbent upon clinicians to rule out other etiologies for ulcerated and/or necrotic skin lesions before implicating spider envenomation. The wrong diagnosis can result in the use of unproven and potentially harmful treatments. (Vetter RS and Bush SP, 2004)
Fatalities resulting from Brown Recluse spider bites are rare. (Furbee RB et al, 2006) Only one death was reported in the aforementioned TESS data base. Victims tend to be children and death is due to vascular collapse and hemolysis.
It’s important for the victim of a Brown Recluse spider bite to remain composed and to seek appropriate medical treatment in a timely fashion. Prior to contacting a primary care provider or emergency department, the wound should be iced (if possible) to reduce any local swelling and/or inflammation. Importantly, heat has been shown to worsen the bite site by extending the area of necrosis. Beyond local wound care and supportive efforts, the optimal management approach for Brown Recluse Spider bites remains unclear. (Furbee RB et al, 2006) A lack of controlled studies, conflicting results from animal and human trials and the often misdiagnosis of brown recluse envenomation have contributed, in part, to this confusion. Treatment approaches have included the use of corticosteroids, colchicine, dapsone, antimicrobials, topical nitroglycerin, hyperbaric oxygen and early surgical excision. In a published review of customary treatment approaches in the primary care setting, there was no evidence that drug therapy affected healing time of suspected bites or the chances of scarring. (Mold JW and Thompson DM, 2004) Interestingly, dapsone and systemic corticosteroids impaired healing whereas dapsone was also associated with more scarring.(Mold JW and Thompson DM, 2004) Antivenin and antiloxosceles Fab fragments hold some promise but are not commercially available for routine use.(Furbee RB et al, 2006) A more thorough review of the pharmacologic management of brown recluse spider bites can be found elsewhere. (Hogan CJ et al, 2004 and Stibich AS and Schwartz RA, 2006 and Swanson DI and Vetter RS, 2005).
The old adage that an ounce of prevention is worth a pound of cure holds true for the Brown Recluse spider. Preventive strategies should include a multidimensional approach aimed at obviating bites all together, stopping spiders from entering the home environment, promoting good sanitary practices around the home and yard and using, when appropriate, approved pesticides. (Jones SC, 2004) Examples of approaches would include inspecting bedding, sealing cardboard boxes, sealing window frames and door jams, using window screens, wearing gloves when working outdoors, removing household clutter, using non-pesticide insect control products and if necessary, approved and safe chemical pesticides.
The Brown Recluse spider is a docile creature. However, when threatened its ability to inflict pain and suffering is formidable despite its small size. Avoidance is the best strategy to obviate an unexpected bite. Yet when a documented or highly suspected envenomation occurs, it’s prudent to promptly seek medical attention so that appropriate wound care measures can be instituted. Family physicians can assist patients presenting with suspected bites by recommending or providing proper first aid measures along with more definitive care, if warranted.
1) Furbee RB, Kao LW and Ibrahim D (2006) Brown recluse spider envenomation. Clin Lab Med; 26:211-26.
2) Hogan CJ, Barbaro KC and Winkel K (2004) Loxoscelism: old obstacles, new directions. Ann Emerg Med; 44: 608-24.
3) Jones SC (2004) Brown Recluse Spider – Extension Fact Sheet.
http://ohioline.osu.edu/hyg-fact/2000/pdf/2061.pdf , accessed June 12, 2007.
4) Mold JW and Thompson DM (2004) Management of brown recluse spider bites in primary care. J Am Board Fam Pract; 17: 347-352.
5) Stibich AS and Schwartz RA (2006) Brown Recluse Spider Bite
www.emedicinehealth.com/spider_bite_brown_recluse_spider_bite/article_em.htm - 34k, accessed July 26, 2007.
6) Swanson Dl and Vetter RS (2005) Bites of brown recluse spiders and suspected necrotic arachnidism. N Engl J Med; 352: 700-707.
7) Vetter RS and Bush SP (2004) Additional considerations in presumptive brown recluse spider bites and dapsone therapy. Am J Emerg Med; 22: 494-5.
8) Watson WA, Litovitz TL, Rodgers Jr GC et al (2005) 2004 annual report of the American Association of Poison Control Centers toxic exposure surveillance system. Am J Emerg Med; 23: 589-666
Copyright Priory Lodge Education Limited 2007
First Published December 2007