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A review of the literature confirms that the brown recluse spider bite is a common and sometimes serious clinical entity. Local and systemic manifestations are extremely variable, thus complicating management of the bite. Pathophysiological studies in laboratory animals yield conflicting results and therapeutic recommendations because of technical and species-specific differences. Standard therapies include aggressive, early debridement as well as systemic and intralesional corticosteroids; however, well-controlled clinical studies to establish their efficacy have not been performed. Variable and unpredictable patient responses to the spider bite necessitate a conservative yet vigilant position in managing these bites.

An extract of brown recluse spider ( Loxosceles reclusa ) venom apparatuses causes death in mice when injected i.p., but causes no local response when sublethal doses are injected s.c. An antiserum was produced against the extract by i.v. injection in a rabbit. Preincubation of a component, isolated from the brown recluse venom apparatus extract, with the antiserum resulted in a loss of its lethal activity in mice. Post-treatment of component-challenged mice with the antiserum was successful if accomplished 0·5 hr after challenge, but not at 1·0 and 2·0 hr.

A purified toxic protein from Loxosceles reclusa venom was assayed for its in vitro effects on the human immunological and blood clotting systems. The toxin caused inhibition of neutrophil chemotaxis, depletion of serum hemolytic complement, prolongation of the activated partial thromboplastin time and depletion of clotting factors XII, XI, IX and VIII by an average of 44% in human plasma. The prothrombin time of human plasma was also prolonged by 1.5-2.0 sec. No effect of the purified toxin was observed on microbicidal ability of neutrophils, the release of enzymes from neutrophils or the adherence of neutrophils to glass beads.

In a prospective study, 31 patients with brown recluse spider bites were treated by either immediate surgical excision or with the leukocyte inhibitor, dapsone, followed by delayed surgical excision. Patients were matched for age, gender, and lesion size and were excluded if the typical history and physical findings were not present. In patients treated with immediate surgical excision (N = 14), delayed wound healing (N = 5) and objectional scarring (N = 7) were common complications. However, pretreatment treatment with dapsone reduced the incidence of wound complications (N = 1) and objectional scarring (N = 1) (p less than 0.05), while reducing the need for surgical excision (N = 1). There were no severe drug reactions due to dapsone, although one patient had persistent G.I. upset. Pretreatment with dapsone not only reduced surgical complications but also improved the outcome of patients bitten by the brown recluse spider.

The Brown recluse spider has emerged into a potent venomous creature. Loxoscelism and necrotic arachnidism is not an infrequent medical problem. Spiders other than L. reclusa are capable of inflicting painful and persisting necrotic wounds, however, management of the local cutaneous lesions are similar. Systemic complications of loxoscelism appear to be characteristic for spiders of the genus loxosceles. The authors review an indepth discussion of the spider, venom, diagnosis, clinical presentation, laboratory findings, treatment, and prevention. The literature on loxoscelism is contradictory because of the individuality of the reaction. Experience with many patients is the only guide to management of these cases.

Experiments with Loxosceles reclusa venom upon invertebrate hosts have revealed both localized and systemic manifestations. Bioassays have yielded LD50 values of 0.42 μg/g ( Acheta domesticus ); 0.33 μg/g ( Galleria mellonella ) and 0.26 μg/g ( Musca domestica ). Evidence for a lytic effect on fat and muscle tissue of Heliothis virescens larvae, hemolymph proteins ( H. virescens ) and hemocytes ( H. virescens, A. domesticus ) has been demonstrated. Observations histochemically showed stronger reactions of protease, lipase, esterase and alkaline phosphatase activity in envenomized H. virescens and M. domestica. L. reclusa venom was separated by gel filtration into three 280 nm absorbing peaks two of which contained components lethal to insects. Peak 1 (high molecular weight) and peak 2 (low molecular weight) produced above control mortality in M. domestica ; whereas, only whole venom and peak 2 aliquots induced increases in the endogenous activity of the ventral nerve cord in Periplaneta americana . When maximally lethal samples of peaks 1 and 2 were combined, observed mortalities were 88% greater than predicted, suggesting either synergism or dependent joint action.

L. D. Foil , J. L. Frazier and B. R. Norment . Partial characterization of lethal and neuroactive components of the brown recluse spider (Loxosceles reclusa) venom. Toxicon17, 347–354, 1979.—Loxosceles reclusa venom was separated by Sephadex G-50 gel filtration into three 280 nm absorbing peaks, two of which contained components lethal to insects. The heavy molecular weight (mol. wt) protein found in peak 1 caused knockdown and mortality in Musca domestica 20–24 hr after injection. The low mol. wt (less than 10,000) polypeptide in peak 2 was heat stable at 90°C and caused knockdown within 30 min and mortality within four hr after injection. Both whole venom and peak 2 contained components which caused a dramatic increase in the amplitude and frequency of the endogenous activity of the ventral nerve cord of Periplaneta americana. The neuroactive factor stimulated this activity to 680-fold and with 5 min produced a block which was reversible by saline irrigation. Gel filtration elutions of the low mol. wt lethal factor and the neuroactive factor overlapped but did not coincide.

A model to study the dermonecrotic effects of a crude fraction of venom from the brown recluse spider (Loxosceles reclusa) was developed using female New Zealand white rabbits. In the rabbit model, surgical excision of the sites of intradermally injected crude venom did not always prevent subsequent necrosis or wound dehiscence despite the use of fluorescein to determine the surgical margin. Heparin and steroids did not prevent the venom-induced necrosis and were much less effective than surgical excision or injecting a specific antivenom. When given within 24 hours, the specific antivenom raised against the brown recluse spider venom blocked or markedly attenuated the toxic effects of the venom in the rabbit model system.

This document is EENY-233 (originally published as DPI Entomology Circular 158), one of a series of Featured Creatures from the Entomology and Nematology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Published: August 2001. Revised: October 2002. https://edis.ifas.ufl.edu/in389

North American loxoscelism caused by the bite of the Loxosceles reclusus , the brown recluse spider, can produce a gangrenous slough at the site of envenomation and a severe systemic reaction. In 16 cases the local reaction included pain, bleb formation, erythema, ecchymosis, necrosis ending in an eschar, and ulceration. The systemic reactions may include fever, nausea, malaise, hemolysis, and thrombocytopenia. Two deaths have been reported in small children. This spider is indigenous throughout the South Central US.

Although the clinical course in this patient's illness was not proven to follow the bite of the brown spider, its characteristics seem identical with the proven cases reported in children. It thus would represent the first fatal case in an adult.

The brown recluse spider, Loxosceles reclusa Gertsch & Mulaik, is frequently reported in Florida as a cause of necrotic lesions in humans. For example, in the year 2000 alone, Loft (2001) reported that the Florida Poison Control Network had recorded nearly 300 alleged cases of brown recluse bites in the state; a subset of 95 of these bites was reported in the 21 counties (essentially Central Florida) under the jurisdiction of the regional poison control center in Tampa. This document is EENY-299 (originally published as DPI Entomology Circular 406), one of a series of Featured Creatures from the Entomology and Nematology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Published: August 2003. EENY299/IN576: Brown Recluse Spider, Loxosceles reclusa Gertsch & Mulaik (Arachnida: Araneae: Sicariidae) (ufl.edu)

Venom from the spider Loxosceles reclusa was extracted by electrical stimulation. The average volume collected from about 3000 females was 0·36 μl per spider. Measured amounts of venom were injected into animals, and of those tested, rats were the most resistant. Mice, guinea pigs and rabbits did show toxic manifestations which could be quantitated.

The objectives in the treatment of the brown recluse spider bite are to prevent skin necrosis and the need for reconstructive surgery. A simple technique that consists of curetting the subcutaneous tissue in the necrotic area of the lesion, to prevent the local destructive actions of the toxin, is described. From 1981 to 1987, 18 patients were treated with this technique. The wounds were generally curetted under local anesthesia in an outpatient setting. In all but one case, the erythema, edema, and pain resolved significantly in 24 to 48 hours, and the wounds healed primarily with minimal scarring. We consider curettage the treatment of choice for brown recluse spider bites when the lesions are noted in relatively early stages. It can be performed as an outpatient procedure; it controls the symptoms and prevents further necrosis, with excellent cosmetic results.

In Reply.— Based on previous experience in an endemic area and our report, Dr Berger questions whether dapsone is indicated for severe brown recluse spider "bites." We agree that (1) not all "bites" should be treated 1 ; (2) in experimental loxoscelism, blood vessels were the primary site of damage; and (3) polymorphonuclear leukocytes (PMNs) were required for extensive cutaneous necrosis. 2 We also point out that in humans, extensive PMN accumulation and perivasculitis are routinely noted 24 to 72 hours after the bite and before skin necrosis (personal observations 3 ). These findings have diagnostic and prognostic implications. In humans, once skin necrosis occurs, lesions persist for weeks. The goal of dapsone therapy is to decrease the ulcerated bite size and speed resolution. In experimental animals, any therapy such as dapsone or specific antivenom that reduced inflammation and PMN infiltration proportionately reduced cutaneous morbidity. Persistent inflammation in bites has been studied

IN 1929, Schmaus1reported the treatment of the first documented case of cutaneous loxoscelism in North America with sedation, starch, and sodium bicarbonate, which was ineffective. Current therapies for brown spider bites, using corticosteroids, antibiotics, antihistaminics, and surgical excision, may not be much more effective management for the skin ulcer that the venom produces.2,3We have treated a documented bite from the brown recluse spiderLoxosceles reclusawith dapsone and produced a dramatic resolution of the skin lesion with no complications. Report of a Case A 27-year-old man killed a spider immediately after being bitten on the right leg while dressing. He went directly to the hospital emergency room, where no treatment was given because he was told that the spider was nonvenomous. He saw his private physician 24 hours later, after the bite site became larger (8×8 cm), swollen, and erythematous. He complained of itching and pain.

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To the Editor.— The dramatic event of severe cutaneous necrosis following brown recluse spider bites has prompted a variety of therapeutic trials. Unfortunately, single reports of successful prevention of necrotic arachnidism can be very misleading. 1 As reported inThe Journal, 2 many of the documented bites produce only erythema and edema or mild hemorrhage and negligible necrosis. The unremarkable bites are most likely caused by small envenomations or protective immunity resulting from previous bites. In lesions destined to go on to significant necrosis, bullae and hemorrhage are usually evident by 24 hours, and a pale, demarcated area is often present at 48 hours. In severe reactions, systemic symptoms begin around 36 hours and include morbilliform rash, urticaria, fever, nausea and vomiting, and occasional hemolysis or diffuse intravascular coagulation. The description of the site at 48 hours in the case report entitled "Dapsone Treatment of a Brown Recluse Bite" 3

Severe cutaneous necrosis is reported commonly as a consequence of Loxosceles spider bites; however, the description of mild cutaneous reactions has been neglected. Knowledge of each extreme will increase our clinical awareness of Loxosceles envenomation. Failure to recognize the mild spider bites has led to inaccurate conclusions regarding prevalence and treatment.

To the Editor.— Necrotic arachnidism caused by Loxosceles reclusa is now recognized to be a prevalent medical problem in mid-United States and especially in Missouri. Other species of poisonous Loxosceles have been more recently identified in the western areas of this country. 1 Venom of this common house spider may cause diffuse intravascular coagulation, 2 thrombocytopenia, hemolytic anemia, hemoglobinuria, and death, as well as the more familiar cutaneous necrosis. 3 Although several other modes of therapy have been used in necrotic arachnidism, steroids given systemically or intralesionally have emerged as the treatment of choice. 3,4 Experiments in animals have not provided evidence to support clinical impressions that these medications are efficacious in preventing necrosis and human studies are not feasible. 5,6 In attempting to affirm the benefit of systemic steroids, 20 New Zealand white female rabbits weighing about 4 kg were injected intradermally with venom that was obtained directly from

Spider envenomation and its consequent discomforts have received much attention lately due to the discovery of the lesions produced by the bite of the brown recluse spider, Loxosceles reclusa Gertsch & Muliak. Although misinformation and rumor have resulted in exaggerated fearfulness of spiders by the general public, it is important to note that spiders do bite people occasionally and possible severe reaction following the bite makes them a public health problem.