Necrotic arachnidism: the mythology of a modern plague

Discovery of a Recombinant Human Monoclonal Immunoglobulin G Antibody Against α-Latrotoxin From the Mediterranean Black Widow Spider (Latrodectus tredecimguttatus)

Widow spiders are among the few spider species worldwide that can cause serious envenoming in humans. The clinical syndrome resulting from Latrodectus spp. envenoming is called latrodectism and characterized by pain (local or regional) associated with diaphoresis and nonspecific systemic effects. The syndrome is caused by α-latrotoxin, a ~130 kDa neurotoxin that induces massive neurotransmitter release. Due to this function, α-latrotoxin has played a fundamental role as a tool in the study of neuroexocytosis. Nevertheless, some questions concerning its mode of action remain unresolved today. The diagnosis of latrodectism is purely clinical, combined with the patient's history of spider bite, as no analytical assays exist to detect widow spider venom. By utilizing antibody phage display technology, we here report the discovery of the first recombinant human monoclonal immunoglobulin G antibody (TPL0020_02_G9) that binds α-latrotoxin from the Mediterranean black widow spider (Latrodectus tredecimguttatus) and show neutralization efficacy ex vivo. Such antibody can be used as an affinity reagent for research and diagnostic purposes, providing researchers with a novel tool for more sophisticated experimentation and analysis. Moreover, it may also find therapeutic application in future.

Latrodectus geometricus (Aranea: Theridiidae) envenoming: Rapid resolution of symptoms following F(ab')2 antivenom therapy

The Brown Widow spider (Latrodectus geometricus) is an invasive species whose geographic range has been expanding worldwide. It is a relative species of the Black Widow and Red-backed spiders of the genus Latrodectus. Despite its broad geographic distribution cases of Brown Widow envenomation have rarely been documented. The venom of L. geometricus is similar to the venom of L. mactans with the primary venom component being alpha-latrotoxin, and consequent envenoming by L. geometricus to humans has resulted in symptoms similar to those reported for other Latrodectus spp. Specific FDA approved Latrodectus antivenom (IgG) available in North America has been effectively used in treating venom-induced symptoms following L. mactans envenoming. The patient reported here involved a confirmed L. geometricus envenoming who was efficaciously treated with an alternately available F(ab')₂ antivenom from Mexico.

Spider bite

Spiders are a source of intrigue and fear, and several myths exist about their medical effects. Many people believe that bites from various spider species cause necrotic ulceration, despite evidence that most suspected cases of necrotic arachnidism are caused by something other than a spider bite. Latrodectism and loxoscelism are the most important clinical syndromes resulting from spider bite. Latrodectism results from bites by widow spiders (Latrodectus spp) and causes local, regional, or generalised pain associated with non-specific symptoms and autonomic effects. Loxoscelism is caused by Loxosceles spp, and the cutaneous form manifests as pain and erythema that can develop into a necrotic ulcer. Systemic loxoscelism is characterised by intravascular haemolysis and renal failure on occasion. Other important spiders include the Australian funnel-web spider (Atrax spp and Hadronyche spp) and the armed spider (Phoneutria spp) from Brazil. Antivenoms are an important treatment for spider envenomation but have been less successful than have those for snake envenomation, with concerns about their effectiveness for both latrodectism and loxoscelism.

[Necrotic arachnidism in the south of France: two clinical cases of loxoscelism]

BACKGROUND

loxosceles spiders are found throughout the world and are responsible for numerous cases of envenomation in America and Southern Europe. We describe, to our knowledge for the first time in France, two clinical cases of cutaneous loxoscelism.

CASE REPORT

two cases of skin necrosis arising after supposed spider bites were grouped together because of their similar clinical presentation: an initial painless bite and rapid development of an inflammatory and painful cutaneous lesion with a central hemorrhagic bulla surrounded by a perimeter of blanched skin (the "red, white, and blue" sign). The outcome in both cases was deep skin necrosis and chronic ulceration requiring surgical treatment.

DISCUSSION

loxoscelism can result in dermonecrosis. Although our cases were not documented by capture of the spider, the diagnosis of cutaneous loxoscelism was supported by the characteristic appearance of the lesion, a typical clinical course, elimination of differential diagnoses, and the confirmed presence of Loxosceles rufescens in the region.

CONCLUSION

loxoscelism can occur in the south of France and although rare, must be considered in this region as a possible cause of skin necrosis.

Misdiagnosis of spider bites: bacterial associates, mechanical pathogen transfer, and hemolytic potential of venom from the hobo spider, Tegenaria agrestis (Araneae: Agelenidae)

The European spider Tegenaria agrestis (Walckenaer) (hobo spider) has been implicated as a spider of medical importance in the Pacific Northwest since its introduction in the late 1980s. Studies have indicated that the hobo spider causes necrotic tissue lesions through hemolytic venom or through the transfer of pathogenic bacteria introduced by its bite. Bacterial infections are often diagnosed as spider bites, in particular the pathogenic bacteria methicillin-resistant Staphylococcus aureus (MRSA). This study examines three aspects of the potential medical importance of hobo spiders in part of its introduced range, Washington State. First, the bacterial diversity of the spider was surveyed using a polymerase chain reaction-based assay to determine whether the spider carries any pathogenic bacteria. Second, an experiment was conducted to determine the ability of the spiders to transfer MRSA. Third, the venom was evaluated to assess the hemolytic activity. We found 10 genera of ubiquitous bacteria on the exterior surface of the spiders. In addition, none of the spiders exposed to MRSA transferred this pathogen. Finally, the hemolytic venom assay corroborates previous studies that found hobo spider venom was not deleterious to vertebrate red blood cells.

"Spider bite" lesions are usually diagnosed as skin and soft-tissue infections

BACKGROUND

Many people seek medical attention for skin lesions and other conditions they attribute to spider bites. Prior experience suggests that many of these lesions have alternate causes, especially infections with community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA).

OBJECTIVES

This study determined the percentage of emergency department (ED) patients reporting a "spider bite" who received a clinical diagnosis of spider bite by their physician vs. other etiologies, and if the diagnoses correlated with demographic risk factors for developing CA-MRSA infections.

METHODS

ED patients who reported that their condition was caused by a "spider bite" were prospectively enrolled in an anonymous, voluntary survey regarding details of their illness and demographic information. Discharge diagnoses were also collected and categorized as: spider bite, bite from other animal (including unknown arthropod), infection, or other diagnosis.

RESULTS

There were 182 patients enrolled over 23 months. Seven patients (3.8%) were diagnosed with actual spider bites, 9 patients (4.9%) with bites from other animals, 156 patients (85.7%) with infections, and 6 patients (3.3%) were given other diagnoses. Four patients were given concurrent diagnoses in two categories, and 8 (4.4%) did not have the diagnosis recorded on the data collection instrument. No statistically significant associations were found between the patients' diagnostic categories and the demographic risk factors for CA-MRSA assessed.

CONCLUSION

ED patients reporting a "spider bite" were most frequently diagnosed with skin and soft-tissue infections. Clinically confirmed spider bites were rare, and were caused by black widow spiders when the species could be identified.

Medical aspects of spider bites

Spiders have been incriminated as causes of human suffering for centuries, but few species worldwide cause medically significant envenomation. Widow spiders (Latrodectus spp.) occur worldwide and cause latrodectism, which is characterized by pain (local and generalized) associated with nonspecific systemic effects, diaphoresis, and less commonly other autonomic and neurological effects. Recluse spiders (Loxosceles spp.) are distributed mostly through the tropical and subtropical Western Hemisphere and can cause severe skin lesions and rarely systemic effects; most bites are unremarkable. Highly dangerous spiders in South America (armed spiders) and Australia (funnel-web spiders) cause rare but severe envenomation requiring medical intervention and sometimes antivenom. Most other spiders involved in verified bites cause minor, transient effects. Many spiders blamed for causing medical mischief have been elevated to medical significance via circumstantial evidence, poor reporting, and repetitive citation in the literature; several species have been shown to be harmless with more stringent scientific evidence involving verified bites in humans.

Enzymatic characterization, antigenic cross-reactivity and neutralization of dermonecrotic activity of five Loxosceles spider venoms of medical importance in the Americas

Loxosceles spiders have a wide distribution in the temperate and tropical regions of the world. Loxoscelism is characterized by necrotic skin ulceration at the bite site and, less commonly, a systemic illness that may be fatal. The purpose of this study was to characterize and compare aspects of the major medically important Loxosceles spider venoms in a standardized manner, particularly considering their neutralization by two Brazilian antivenoms. By SDS-PAGE (12% acrylamide), Loxosceles deserta, Loxosceles gaucho, Loxosceles intermedia, Loxosceles laeta and Loxosceles reclusa venoms had similar electrophoretic profiles, with the major protein bands of 32-35 kDa. All venoms exhibited gelatinolytic, caseinolytic and fibrinogenolytic activities in vitro with a large array of proteases, mainly between 18.1 and 31.8 kDa. Most of these enzymes were metalloproteases as this activity was abolished by 1,10-phenanthroline. Hyaluronidase activity was detected in a protein band of approximately 44 kDa in all venoms. Sphingomyelinase activity was demonstrated in all five venoms. Antigenic cross-reactivity, by Western blotting, was also observed among all venoms studied using commercial equine antivenoms produced in Brazil (Institute Butantan and CPPI). These antivenoms recognized mainly components between 25 and 40 kDa in all venoms with several minor components of >89 kDa. Strong cross-reactivity was also seen among all venoms through the ELISA technique (titre range: 64,000-512,000). All venoms (5 microg doses) induced a similar local reaction when injected intradermally into the flank of rabbits, demonstrating dermonecrosis, hemorrhage, vasoconstriction, edema, and erythema. However, no reaction was observed when each venom was pre-incubated (1 h, 37 degrees C) with Brazilian commercial sera prior to injection. The antivenoms also abolished the sphingomyelinase activity in vitro, suggesting the venoms of the major medically important Loxosceles spider species have generally similar toxic and enzymatic characteristics. Thus, as Brazilian commercial antivenoms are able to neutralize the dermonecrosis induced by Loxosceles venoms of diverse geographical origin, clinical studies should be undertaken on the potential for a single global Loxosceles antivenom.

Reports of envenomation by brown recluse spiders (Araneae: Sicariidae) outnumber verifications of Loxosceles spiders in Florida

Bites attributed to the brown recluse spider, Loxosceles reclusa Gertsch & Mulaik, are frequently reported by medical personnel throughout Florida, whereas the extensive arachnological evidence contradicts the alleged widespread occurrence of Loxosceles spiders in the state. We compared reports of brown recluse spider bites made by medical personnel from a 6-yr Florida poison control center database to the known verifications of Loxosceles spiders from 100 yr of Florida arachnological data. Medical personnel diagnosed 124 brown recluse spider bites from 31 of Florida's 67 counties in 6 yr. In contrast, only 11 finds of approximately 70 Loxosceles spiders have been made in 10 Florida counties in 100 yr. Florida does not have sufficient widespread populations of Loxosceles spiders to warrant consideration of brown recluse spider envenomation as a probable etiology of dermonecrosis. Florida health care would improve if medical personnel would consider the multitude of other etiologies that manifest in dermonecrosis.