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Diagnoses of brown recluse spider bites (loxoscelism) greatly outnumber actual verifications of the spider in four western American states

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Abstract

We attempt to demonstrate that physicians overdiagnose loxoscelism (colloquially known as 'brown recluse spider bites') by comparing the numbers of such diagnoses to the historically known numbers of Loxosceles spiders from the same areas in four western American states. The medical community from non-endemic Loxosceles areas often makes loxoscelism diagnoses solely on the basis of dermonecrotic lesions where Loxosceles spiders are rare or non-existent. If these diagnoses were correct then Loxosceles populations should be evident, specimens should readily be collected over the years and there should be a reasonable correlation between diagnoses and spider specimens. In 41 months of data collection, we were informed of 216 loxoscelism diagnoses from California, Oregon, Washington and Colorado. In contrast, from these four states, we can only find historical evidence of 35 brown recluse or Mediterranean recluse spiders. There is no consistency between localities of known Loxosceles populations and loxoscelism diagnoses. There are many conditions of diverse etiology that manifest in dermonecrosis. In the western United States, physician familiarity with these conditions will lead to more accurate diagnoses and subsequent proper remedy.

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... The typical "brown recluse spider bite" patient often describes waking up with a small bump, red mark, or bite mark that progressively increases in size, soreness or pain, redness, and swelling with later development of a necrotic core (3)(4)(5)(6). Very few patients report seeing the spider bite them, let alone bring the spider in to confirm its species and instead are empirically diagnosed with a brown recluse spider bite (1,2,(7)(8)(9)(10). However, a strong effort by physicians who are experts on spider and other arthropod bites has vehemently rejected the notion that brown recluse spiders are causing these lesions (1,2,(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18). ...
... Very few patients report seeing the spider bite them, let alone bring the spider in to confirm its species and instead are empirically diagnosed with a brown recluse spider bite (1,2,(7)(8)(9)(10). However, a strong effort by physicians who are experts on spider and other arthropod bites has vehemently rejected the notion that brown recluse spiders are causing these lesions (1,2,(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18). They argue that spiders, by nature, are not aggressive and will not attack unless provoked and should thus always be found in one's close proximity. ...
... Furthermore, physicians have reported brown recluse spider bites across the country, but the spiders have definitively been found only in a few states in the southern and central U.S. (7). Several studies have demonstrated that the number of diagnoses of spider bites far exceeds the actual number of brown recluse spiders (8)(9)(10). These experts found that patients initially diagnosed with brown recluse spider bites were later diagnosed with a variety of other medical conditions that also cause dermatonecrotic lesions, including various bacterial, fungal, or viral infections, vasculitides, other autoimmune disorders, other acquired dermatologic conditions, etc. (7,10). ...
... A variety of medical conditions of diverse causes manifesting in dermonecrosis have been misdiagnosed as necrotic spider bite. 14,25,26 Without substantial validation of verified hobo spider envenomation effects, the medical community will misdiagnose presumptive hobo spider bites. This parallels a striking similarity to the brown recluse spider, which is erroneously blamed for necrotic lesions throughout North America, including states or regions where brown recluses are exceedingly rare or have never been found. ...
... This parallels a striking similarity to the brown recluse spider, which is erroneously blamed for necrotic lesions throughout North America, including states or regions where brown recluses are exceedingly rare or have never been found. 23,25,[27][28][29] Although hobo spiders may rarely cause necrotic lesions, it seems that, at the least, its role in North American dermonecrosis is still unproven and, at the most, the hobo spider might be erroneously implicated. Preliminary corroboration shows that hobo spiders are not considered medically significant in its native Europe; Binford 30 found no differences in venom composition between European and American T agrestis spiders and suggested that the hobo spider has been wrongly accused of causing necrotic skin lesions. ...
... A similar argument has demonstrated that recluse spiders are highly unlikely to cause many suspected cases of necrotic arachnidism reported from nonendemic areas. 25,29 Necrotic lesions of unknown etiology should not be immediately attributed to spider bites, and we vigorously appeal for validation of hobo spider incrimination lest erroneous information continue to proliferate that can only be detrimental to proper health care. Incorrect diagnosis of necrotic ulcers as spider bites (eg, basal cell carcinoma, 14 anthrax, 33 bacterial and fungal infections 26 ) delays or prevents appropriate treatment, sometimes resulting in significant morbidity. ...
Article
Richard S. Vetter, MSGeoffrey K. Isbister, MDFrom the Department of Entomology, University of California–Riverside (Vetter), Riverside, CA; the Biology Division, SanBernardino County Museum (Vetter), Redlands, CA; and theDiscipline of Clinical Pharmacology, Newcastle Mater MisericordiaeHospital (Isbister), Waratah, New South Wales, Australia.[Ann Emerg Med. 2004;44:605-607.]
... 4,5 In a retrospective analysis of suspected brown recluse bites in four western American states over a 41-month period, Vetter and others collected 216 diagnoses of brown recluse spider bites, but could only confirm 35 recluse sightings in those same four states over the study period." 6 "Ulcerating or necrotic wounds from a myriad of other insect-induced, infectious, or physical sources are often misdiagnosed as Loxosceles reclusa bites with necrotic araneism in the United States. Systemic loxoscelism is also rare in the United States, with a 3% incidence rate and no deaths in a population of 111 patients with expert-confirmed brown recluse (Loxosceles reclusa) bites in a 1997 survey in the United States. ...
... 4−6 Since the hobo spider is considered innocuous in Europe, however, it remains unclear and unproven whether the US hobo spider is really the major cause of necrotic araneism in the North American Pacific Northwest." [4][5][6]10,11 "In an elegant laboratory investigation designed to compare the venom toxicities of hobo spiders from the United States and Europe, Binford analyzed the venoms of Tegenaria agrestis spiders from Washington, the United Kingdom, and Switzerland by both liquid chromatography and insect bioassays. 11 Chromatographic profiles were different between the sexes, but similar within sexes between hobo spiders from the United States and the United Kingdom. ...
... 11 In several recent studies of necrotic araneism and spider ranges, Vetter and others concluded that the majority of dermonecrotic lesions in the United States are misdiagnosed as necrotic araneism from spider bites, particularly Loxosceles reclusa and Tegenaria agrestis bites, especially in regions where such species are either not endemic or rarely reported." [4][5][6] It was not my intent to exaggerate the topic of necrotic araneism, especially "non-Loxosceles" araneism, but to present the controversy in an unbiased manner. History will recall a rather embarrassing situation in Australia, where for a decade or so, the white-tail spiders of the Lampona species were wrongly accused of causing dermonecrotic bites, until the "myth was debunked" by Isbister and Gray in 2003. ...
... These data also showed a great distance between some of the taxa, as in the group of spiders, there were 18 genera from 15 different families originating from 13 American states and the District of Columbia. Since 1957, Loxosceles bite diagnoses have been made throughout North America, even in areas where there is no reported occurrence of these spiders (Vetter 2000;Vetter and Bush 2002a, b;Vetter et al. 2003Vetter et al. , 2004Bennett and Vetter 2004;Swanson and Vetter 2005), although data from the American Association of Poison Control Centers' National Poison Data System (NPDS) have shown a decrease in accidents with Loxosceles spiders over the years. Annual reports from the NPDS showed 1326 cases in 2013 (Mowry et al. 2014), 1185 cases in 2015 , 1116 cases in 2016 ) and 898 cases in 2017 (Gummin et al. 2018). ...
... Analyzing the publications about loxoscelism diagnosis, it is possible to detect a great concern of certain authors with the overestimation of loxoscelism, mainly in the USA (Vetter et al. 2003), as mentioned above. However, it is also important to look at the problem from the opposite point of view. ...
Article
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The genus Loxosceles comprises 140 species widely distributed around the world. These spiders are nocturnal, sedentary and remarkably nonaggressive, although they cause accidents in humans with wide degrees of severity, generating signs and symptoms that define the clinical condition known as loxoscelism. Its local signs and symptoms were first reported in 1872, and over the years, a large medical literature has been accumulated; unfortunately, it is not always trustworthy. Assessing the reliability of such information, we reviewed 120 case reports of loxoscelism published in 84 articles over the past 20 years. This search allowed us to gather information on the clinical aspects, diagnosis and treatment of loxoscelism, showing that the severity of these accidents has multiple degrees and that it is influenced by many factors. Thus, coupled with epidemiological and species occurrence information, this study can be a useful tool for the clinical practice of loxoscelism. It may support and provide a multidisciplinary view that should be taken into consideration when establishing the therapeutic approach in cases of Loxosceles envenomation.
... Spiders of the genus Loxosceles Heineken & Lowe, 1832 are better known in North America as "violin spiders", "recluse spiders", or "brown recluse spiders"; commonly known by the medical community and general public to cause dermonecrotic lesions caused by their poisonous bites and the venom component, Sphingomyelinase D, an enzyme that destroys endothelial cells lining the blood vessels (Vetter and Barger 2002;Vetter and Bush 2002;Vetter et al. 2003Vetter et al. , 2009Wendell 2003;Da Silva et al. 2004;Vetter 2005Vetter , 2008Vetter , 2015Sandidge and Hopwood 2005;Ramos-Rodríguez and Méndez 2008;Manríquez and Silva 2009;Swanson and Vetter 2009). The genus Loxosceles belongs to the spider family Sicariidae Keyserling, 1880, which comprises three genera: Hexophthalma Karsch, 1879, with six species from Africa, Sicarius Walckenaer, 1847, with 21 species distributed in Central and South America, and Loxosceles, with 134 described species worldwide (Magalhães et al. 2017;World Spider Catalog 2018). ...
... Some North American synanthropic species of Loxosceles, such as L. reclusa in the United States, have been closely studied for their biological, medical and physiological aspects, analyzing their abundances, distribution and natural history (Vetter and Barger 2002;Vetter and Bush 2002;Vetter et al. 2003Vetter et al. , 2009Wendell 2003;Vetter 2005Vetter , 2008Sandidge and Hopwood 2005;Swanson and Vetter 2009). However, these aspects are poorly known for species from Mexico. ...
Article
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A new species of the spider genus Loxosceles Heineken & Lowe, 1832, Loxoscelesmalintzisp. n. , is described from the states of Puebla, Morelos and Guerrero, in the central region of Mexico. The description is based on adult males and females with morphological and ultra-morphological images. Updated distribution maps are provided for the 39 species recorded from the Mexican territory (including the new species). The states with the greatest diversity are Baja California Sur, Baja California and Sonora, with five species each. A total of 441 records for the 39 species, based on arachnological collections, data bases and literature, were used to update the distribution maps. Loxoscelesboneti Gertsch, 1958 is the species with the highest number of records in Mexico, with a total of 58 records from different localities. The states with the most records so far are Guerrero, with 55 records, Morelos, with 35 records, and Baja California Sur, with 30 records. Loxoscelesrufescens (Dufour, 1820), an introduced species, is recorded for the second time in Mexico, from the state of Chihuahua, being the first well-documented record for the country. Mexico has the greatest diversity of species of Loxosceles worldwide, with 39 (two introduced species) of the 134 described species. Additionally, biogeographical comments for the species from Mexico are provided.
... Therefore, the still growing body of medical Loxosceles literature is primarily not reliable and in consequence wrong. There are numerous analyses and reviews dealing with this context, among others White et al. (1995), Vetter et al. (2003), Swanson and Vetter (2005, Vetter (2005, Vetter and Isbister (2008), Stuber and Nentwig (2016), and Stoecker et al. (2017). ...
... Cutaneous necrosis is a variable syndrome, easy to confuse with similar syndromes, which can be caused by a variety of agents (Vetter et al., 2003;Swanson and Vetter, 2005;. Many medical conditions can cause cutaneous necrosis including infections of bacteria (Staphylococcus including methicillin resistant varieties (MRSA) and Streptococcus transmitted diseases, Lyme disease, cutaneous anthrax, syphilis, tularemia, impetigo), virus (herpes simplex, herpes zoster), and fungus (sporotrichosis, aspergillosis). ...
Article
Loxosceles rufescens is a circum-Mediterranean spider species, potentially harmful to humans. Its native area covers the Mediterranean Basin and Near East. Easily spread with transported goods, it is meanwhile an alien and invasive species to nearly all other continents and many islands. This species occurs in semi-arid steppe-like habitats, typically under stones and in cavities, which enables it to settle inside buildings when invading the synanthropic environment. This review analyses the literature of L. rufescens bites to humans (38 publications) of which only 11 publications refer to 11 verified spider bites (10% of the reported bites). Two published allegedly deadly spider bites (Thailand 2014 and Italy 2016) involve non-verified spider bites and are thus not reliable. The symptoms and therapy of these 11 verified bites are described: only five cases showed moderate systemic effects, nine cases developed necrosis, four cases needed surgical debridement, all cases healed without complications within a few weeks. In conclusion, L. rufescens is a spider species globally spread by human activity, it rarely bites humans and the bites are less harmful than often described. There is no known fatal issue.
... We do so by outlining the detrimental impacts of spiders on humans through envenomation. Although venomous spiders are only found in certain regions of Canada (Bennett 2001;Kasumovic and Andrade 2004;Salomon, Vibert and Bennett 2010), it should be noted that many Canadians suffer from arachnophobia and misdiagnoses of spider bites (Vetter et al. 2003a;Vetter et al. 2003b;Bennett and Vetter 2004). Since Australia features a number of venomous spiders and these encounters have been relatively well documented, four major culprits for arachnophobia and fears of spiders in general have been highlighted. ...
... Some researchers (Vetter et al. 2003a;Vetter et al. 2003b;Bennett and Vetter 2004) have begun addressing human-arachnid interactions by challenging the misdiagnoses of spider bites. Such research is crucial so that appropriate medical strategies are implemented and that knowledge of which spider species are actually harmful is provided. ...
Article
Full-text available
Considering the fear that spiders can generate in humans, examining human–spider interactions in urban settings may at first glance appear odd. However, human–spider interactions, which occur quite frequently in urban settings, do not necessarily have to be negative; they can, in some cases, foster respect and tolerance (sometimes through avoidance). When one considers how global transformations, invasive species, urbanization, and adaptation will impact human–spider interactions, a review of the literature pertaining to these encounters is timely. We begin this discussion by describing spiders and providing an overview of some of their positive and negative impacts. Challenges regarding species identification and envenoming are also discussed. After the role of biological, psychological, and social aspects in human–spider interactions are re-examined, we provide future options aimed at organizing broad-scale public programs for five specific target groups: 1) the general public, 2) health professionals, 3) educators, 4) naturalists, and 5) researchers. In the conclusion, we provide potential management and educational strategies aimed at increasing our knowledge and tolerance of these animals in urban settings.
... Typically, neither physicians nor patients are properly educated in spider identification, probably because spider bites are considered to be rare events. Therefore, it is not unexpected that cases formally diagnosed as spider bites often proved to be incorrect when verified by experts (e.g., Russell and Gertsch, 1983;Schenone, 1996;Vetter, 2000;Vetter et al., 2003). The verification process involves three steps and is currently recognized as the international standard for a 'verified spider bite': First, the spider bite has to be observed; second, the spider must be caught during, or immediately after the bite and sent to an expert for identification; and third, the bite must cause symptoms such as pain or discomfort, usually associated with spider bites (Isbister and White, 2004;Vetter and Isbister, 2008). ...
... Medical diagnoses of a 'spider bite' are usually incorrect, as most injuries attributed to spider bites by patients or physicians turned out to be caused by something else. Often they represent a wide range of dermatoses, infections, allergic reactions, or bites and stings by arthropods other than spiders (such as fleas, bed bugs, ticks, mosquitoes) (e.g., Russell and Gertsch, 1983;Schenone, 1996;Vetter, 2000Vetter, , 2008Vetter et al., 2003). The reason for this is most likely due to the relatively poor ability of both physicians and patients to distinguish spiders, either from other arthropods or from each other. ...
Article
During a two-year study, all spider bites recorded by Swiss primary care physicians were reported to the Swiss Toxicological Information Centre and all collected spiders were identified. A total of 14 verified spider bites were recorded, involving five species from four families: Zoropsis spinimana (five cases), Cheiracanthium punctorium (four cases), Tegenaria atrica (three cases) and one case of Malthonica ferruginea (= Tegenaria ferruginea) (both Agelenidae), and one case of Amaurobius ferox (Amaurobiidae). The bites of all spider species produced relatively mild symptoms. Local symptoms such as moderate to severe pain, circumscribed swelling and redness were the only effects in most cases. Systemic symptoms were rare. There was complete recovery in all cases and all lesions healed completely without further damage or secondary disorders. Following a review of the European spider bite literature, the number of spider species capable of biting humans in Europe is considered to be much larger than could be concluded from this study. Most spider bites are restricted to species living synanthropically, thus promoted by climate and habitat change. The annual frequency of spider bites in Switzerland is estimated at 10-100 bites per million inhabitants, but this is predicted to increase due to the continuous arrival of new alien species, many of which have a high potential to establish in urban areas.
... Likewise, L. reclusa is extremely abundant in central to eastern Oklahoma and Kansas, however, there are no state publications known to me detailing this distribution. As the brown recluse is not native to Colorado (Vetter et al. 2003), the range terminates somewhere east of the Colorado border. For Louisiana, Mississippi and Alabama, there are inconsistencies between the published Cooperative Economic Insect Report map of Gorham (1968) and other sources of information. ...
... Using as much taxonomic information as was available (museum and personal arachnological collections, correspondence with municipal agencies that receive spiders for identification [e.g., state diagnostic clinics, departments of public and environmental health, department of food and agriculture]) and comparing it to the number of alleged incidents of Loxosceles envenomation (e.g., published report or tallies of physician loxoscelism diagnoses, poison control center data bases, physician questionnaire responses), in nonendemic Loxosceles regions of North America, the number of loxoscelism diagnoses always outnumbered the verified number of Loxosceles spiders for such areas as Colorado and the Pacific coast states (Vetter et al. 2003), Florida (Vetter et al. 2004), Canada (Bennett & Vetter 2004), South Carolina (Frithsen et al. 2007) and Pennsylvania (Vetter et al. unpubl. data). ...
Article
Loxosceles spiders are of concern outside of the arachnological world because their bites can cause occasional necrotic skin lesions and/or systemic complications; these manifestations are known as loxoscelism. Once these spiders became well associated as medical entities, much notoriety was attained through the publication of medical case histories as well as tales of horrific wounds in the general literature. Although most Loxosceles spider bites are unremarkable, require only general supportive care, and often result in excellent outcome, they are an occasional source of severe dermonecrotic injury with long healing times and significant scarring. In rare cases of systemic loxoscelism, serious intravascular, nephrological and/or multi-organ damage can occur, sometimes resulting in death. However, also of concern is that loxoscelism is diagnosed by medical personnel or presumed by the general public in highly improbable scenarios preventing or delaying proper remedy, which can lead to deleterious outcome. Herein, Loxosceles spider biology and medical aspects are reviewed. In particular, an extensive discussion of the distribution of the brown recluse spider, L. reclusa Gertsch & Mulaik 1940, is presented along with life history characteristics, which relate to the medical aspects of the genus. Also presented are manifestations and epidemiology of loxoscelism, misdiagnoses of bites by the medical community, alternative diagnoses confused with recluse spider bites and a discussion of the psychological basis for the proliferation of the myth of loxoscelism by both the general public and the medical community. North and South American species are reviewed because this is where the genus predominates and is the region where the most pertinent research has originated.
... The brown recluse spider (Loxosceles reclusa, Gertsch & Mulaik, 1940) (Sicariidae) is well-known as a medically important spider of North America. The potential for serious necrotic skin lesions (i.e., loxoscelism) and, rarely, systemic complications from its bite, has led to its notoriety as well as much misinformation and misdiagnoses of skin lesions (Vetter & Bush 2002;Vetter et al. 2003Vetter et al. , 2004Bennett & Vetter 2004;Frithsen et al. 2007). Perhaps as a result, since the seminal study of basic biology by Hite et al. (1966), most research on this species has focused on its venom, the pathology and etiology of bites, potential treatments, and distribution (reviewed in Vetter 2015). ...
Article
Full-text available
We studied dispersal of brown recluse spiders, Loxosceles reclusa (Gertsch & Mulaik, 1940), around an infested urban garage using pitfall traps. Over a four-month period, 23 were captured from a source population that averaged 100 individuals observed in nocturnal censuses. Loxosceles reclusa were captured in far lower proportions compared to their potential source population size than were other spiders such as theridiids and agelenids that also resided in the garage, albeit in far lower numbers. Dispersal was weakly positively correlated with the source population size. We compare our findings to anecdotal reports from prior studies and the general consensus that brown recluse spiders are poor dispersers to argue for more detailed examination of the movement and specific habitat requirements of this medically important spider. Habitat specificity and high mortality during dispersal may help explain the highly clustered spatial distribution of brown recluse spiders, not only a lack of attempted emigration.
... Their bite can cause a clinical condition known as loxoscelism, which is characterized by cutaneous necrosis in mammals [2]. Loxoscelism was not documented until the mid-twentieth century, and it has often been misdiagnosed [3] because its symptomatology is similar to other affections [4]. Even so, there are known cases across the entire distribution range of the genus, including the Mediterranean Basin, where Loxosceles rufescens (Dufour 1820) is widely distributed [1,3,5,6]. ...
Article
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The species Loxosceles rufescens is native to the Mediterranean but considered cosmopolitan because it has been dispersed worldwide. A previous study revealed 11 evolutionary lineages across the Mediterranean, grouped into two main clades, without any clear phylogeographic pattern. The high genetic diversity within this species (p-distances of up to 7.8% in some Mediterranean lineages), together with the results obtained with different species delimitation methods (GMYC, TCS) could indicate the existence of cryptic species. Here we compare the mitochondrial and microsatellite diversity to elucidate if the lineages of L. rufescens in the Mediterranean should be considered different species (cryptic species) or populations of the same species. To do so, we analyzed the cox1 diversity of 196 individuals, of which, we genotyped 148, sampled from 19 localities across the Mediterranean. STRUCTURE analyses of microsatellite data identified two genetic clusters of L. rufescens. One cluster included individuals from Western Mediterranean localities (Iberian Peninsula, Morocco, Balearic Islands) and Israel, while the second one grouped individuals from Italian and Greek localities, including Sardinia, Sicily and Tunisia. These patterns suggest that geographic proximity is the more significant factor in the clustering with microsatellite data and shows the existence of gene flow between the nearest geographic areas, even if the individuals belong to different mitochondrial lineages or clades. The lack of correspondence between both genetic markers suggests that the evolutionary lineages found within L. rufescens should not be considered different species. We conclude that these phylogenetic linages and their distribution may be the result of the maternal evolutionary history of the species and human-mediated dispersion.
... 3 Numerous cases are reported in regions outside the L. reclusa habitat. 4 As yet, no reliable test has been marketed to distinguish actual Loxosceles reclusa envenomations from similar wounds. To help increase diagnostic accuracy, Sams et al. 5 , and more recently Rader et al. 1 The original Sams criteria provided three grades of lesion criteria: atypical lesion, compatible lesion, and typical lesion. ...
Article
We report an atypical course of a likely brown recluse spider bite in a 79-year-old male. The Rader scale and Loxosceles reclusa venom detection by ELISA provide supporting evidence for a loxoscelism diagnosis. Obtundation and myocardial infarction occurred following a drop in hemoglobin to 6.5g/dL. The rapid loss of blood volume was considered a significant etiologic factor for both the obtundation and myocardial infarction. The neurological symptoms reversed rapidly after packed red blood cell transfusion.
... Furthermore, different studies have shown that many arachnid accidents are reported in non-endemic regions, where spiders of the reported genus have never been found by entomologists [14][15][16]. In addition, many conditions of different etiologies (such as infection by Staphylococcus) bring out skin injuries similar to lesions caused by spider bites, leading to wrong diagnosis by clinicians [12,17]. ...
Article
Full-text available
Diagnostic tests for arachnid accidents remain unavailable for patients and clinicians. Together with snakes, these accidents are still a global medical concern, and are recognized as neglected tropical issues. Due to arachnid toxins' fast mechanism of action, quick detection and quantification of venom is required to accelerate treatment decisions, rationalize therapy, and reduce costs and patient risks. This review aims to understand the current limitations for arachnid venom identification and quantification in biological samples. We benchmarked the already existing initiatives regarding test requirements (sample or biomarkers of choice), performances (time, detection limit, sensitivity and specificity) and their validation (on animal models or on samples from envenomed humans). Our analysis outlines unmet needs for improving diagnosis and consequently treatment of arachnid accidents. Hence, based on lessons from past attempts, we propose a road map for raising best practice guidelines, leading to recommendations for future progress in the development of arachnid diagnostic assays. Key Contribution: This review aims to assimilate past experiences on arachnid accident diagnosis and propose directions for future development of a diagnostic kit in this field. Unmet needs are outlined; test requirements are discussed; and a road map for arachnid diagnostic assay development based on best practice guidelines is proposed.
... We are, however, not aware of any report from Europe referring to bites from these species. Th is is in line with the general assumption that the frequency of spider bites is overestimated (Vetter et al. 2003). Additionally it may be possible that these alien species did not reach relevant densities or that they even did not establish in the long term. ...
Article
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A total of 47 spider species are alien to Europe; this corresponds to 1.3 % of the native spider fauna. They belong to (in order of decreasing abundance) Theridiidae (10 species), Pholcidae (7 species), Sparassidae, Salticidae, Linyphiidae, Oonopidae (4-5 species each) and 11 further families. There is a remarkable increase of new records in the last years and the arrival of one new species for Europe per year has been predicted for the next decades. One third of alien spiders have an Asian origin, one fifth comes from North America and Africa each. 45 % of species may originate from temperate habitats and 55 % from tropical habitats. In the past banana or other fruit shipments were an important pathway of introduction; today potted plants and probably container shipments in general are more important. Most alien spiders established in and around human buildings, only few species established in natural sites. No environmental impact of alien species is known so far, but some alien species are theoretically dangerous to humans.
... Uygun örümceklerin bölgede bulunup bulunmadığı bilinmese bile nekrotik deri yaraları sıklıkla loksoscelizm olarak sınıflandırılırlar: 216 "kahverengi münzevi örümcek" ısırık teşhisinden sadece 35'inde Loxosceles reclusa türünün ilgili coğrafik bölgede bulunduğu kesin olarak bilinmektedir (37). Kene ısırığına karşı ciddi reaksiyonlar ve Lyme hastalığında görülen kızarıklıklar münzevi örümcek ısırıkları ile karıştırılabilir (22). ...
Chapter
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Translation from Patrick R. Murray, P.R., Baron, E.J, Jorgensen, J.H. & M. L. Landry, (2007). “Manual of Clinical Microbiology (9th Ed.). ASM Pres. 2256pp.
... As in other reports in this study the crucial factors in reaching a probable diagnosis of spider bite, mostly latrodectism were the knowledge and experience of clinical toxicologists, epidemiological features, typical seasonal distribution and occurrence in farming and outdoor activities [21][22][23] . The case history is one of the most important elements, forming the essential basis for a plausible assessment of a case of disease, especially when the lack of knowledge in the spider semiology is present [22] . ...
Article
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We performed a retrospective study of 176 patients in the University Hospital Center of Tirana (Albania), during the period 2001–2011, admitted with the diagnosis of a suspected spider bite. Three fatalities were registered during this decade covered from our study, with a clinical picture of marked hypertension, tachycardia and acute cardiac failure leading to death within a minimum of 25 h and a maximum of 42 h from the occurrence. Out of the total of 176 patients, we had 59% (104 cases) females, and 41% males. The overwhelming majority of the patients lived in rural areas (155 of the cases); extremities were mostly affected from the bites. A summary of clinical signs and a brief review of the available literature are made in the results and discussion section of this paper. Authors advocate that special precautions should be taken especially in severe forms of interesting autonomous nerve system, with aggressive fluid resuscitation, supportive therapy and close monitoring of vital signs.
... Although Loxosceles bites are scarce (Vetter & Barger, 2002), they can produce serious dermonecrotic lesions, a condition medically known as loxoscelism (Swanson & Vetter, 2006). However, misidentification of biting spiders could over-diagnose loxoscelism (Vetter, 2003) and complicate further understanding of its medical importance. Thus, providing a reliable DNA barcode reference library with tested efficacy would facilitate this first step in the correct management of loxoscelism (Planas et al., 2015). ...
Article
We conducted an integrative taxonomic study of a radiation of Loxosceles spiders endemic to the Canary Islands combining molecular (mtDNA and nDNA) and morphological data. This led to the formal description of six new species: Loxosceles mahan sp. nov. endemic to Fuerteventura, Lanzarote, and adjacent islets; Loxosceles bentejui sp. nov. and Loxosceles tazarte sp. nov. both endemic to Gran Canaria; Loxosceles guayota sp. nov. and Loxosceles tibicena sp. nov. both endemic to Tenerife; and Loxosceles hupalupa sp. nov. endemic to La Gomera and El Hierro. These new species are included in the Loxosceles rufescens group, and are clearly distinguished from L. rufescens by a conspicuous dark V-mark posteriorly on the pars cephalica, the embolus length, and the shape of seminal receptacles. Given that a crucial step for the development of proper health management is the correct identification of the species involved in bite accidents, we additionally tested the efficacy of DNA barcoding as a fast and reliable tool for identifying the Loxosceles species found in the Canary Islands, including the human-introduced L. rufescens.
... En dehors des cas exceptionnels pour lesquels une araignée responsable a été récupérée et formellement identifiée, nous devons considérer que le loxoscélisme est un diagnostic d'élimination. Plusieurs articles récents dénoncent ainsi l'abus de diagnostic erroné de loxoscélisme en zone d'endémie alors que les patients présentaient des pathologies bien différentes : leishmaniose, mal perforant plantaire, syphilis, impétigo, périartérite noueuse, maladie de Lyme, pyoderma gangrenosum, et bien d'autres [76] . ...
Article
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Les animaux venimeux produisent un venin qui est généralement injecté par un appareil venimeux lors de morsures ou de piqûres. Plusieurs groupes de vertébrés ou d'arthropodes sont capables de provoquer des envenimations graves avec parfois mise en jeu du pronostic vital. Si les hyménoptères sont responsables du plus grand nombre d'envenimations, les serpents et les scorpions sont à l'origine d'un haut niveau de morbidité/mortalité dans plusieurs pays tropicaux, avec des espèces induisant des envenimations aux tableaux cliniques complexes et avec difficultés thérapeutiques (intérêt discuté des antivenins, de la chirurgie, des antibiotiques, de la prise en charge en soins intensifs...). Ces difficultés expliquent pourquoi serpents et scorpions représentent dans de larges zones géographiques (Asie du Sud, Afrique, Amérique latine) un véritable problème de santé publique. Plusieurs espèces d'araignées, de myriapodes ou de chenilles peuvent aussi injecter leur venin avec parfois pour conséquence des symptômes systémiques graves. Bien qu'elles ne soient impliquées que dans des observations sporadiques, ces espèces doivent aussi être considérées comme des animaux venimeux terrestres potentiellement dangereux. Les différents tableaux cliniques lors de l'exposition à des venins dans les biotopes terrestres sont présentés dans le but d'évaluer les répercussions de cette fonction venimeuse sur la santé humaine.
... La sobrenotificación no ocurre sólo en nuestro país, sino que sería común, 6 por una mala identificación del ejemplar o por adjudicarle a Loxosceles una dermonecrosis de origen desconocido. 7,8 Son arañas muy poco agresivas, hecho constatado directamente por los autores mediante el hallazgo de construcciones altamente infestadas por Loxosceles laeta y habitadas por seres humanos desde hace casi un siglo, en las que jamás se comunicó un accidente debido a estas arañas. Justamente, las características del hábitat de las Loxosceles, revisten importancia en pediatría. ...
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Loxosceles es una araña de distribución mundial con características sinantrópicas. Su picadura se caracteriza por necrosis cutánea que, en un bajo porcentaje de casos, se acompaña de manifestaciones sistémicas. En los cuadros sistémicos la mortalidad puede ser elevada. No existen métodos de laboratorio para el diagnóstico asistencial, que se realiza por los signos clínicos y la identificación de los ejemplares. El tratamiento específico es la aplicación del antiveneno. El objetivo de esta presentación es brindar una actualización sobre las características de este envenenamiento, su diagnóstico y tratamiento dirigidos hacia el paciente pediátrico.
... Une reprise chirurgicale à visée reconstructrice ne sera donc envisagée qu'après stabilisation des lésions. En dehors des cas exceptionnels pour lesquels une araignée responsable a été récupérée et formellement identifiée,le loxoscélisme est un diagnostic d'élimination.Plusieurs articles ont dénoncé l'abus de diagnostic erroné de loxoscélisme en zone d'endémie alors que les patients avaient des pathologies bien différentes : leishmaniose, mal perforant plantaire, syphilis, impétigo, périartérite noueuse, maladie de Lyme, pyoderma gangrenosum, et bien d'autres [42][43][44][45] . ...
Article
•Limited risks Although most species of spiders are venomous, only ten or so are able to induce human envenomations.•From a systematic point of view, it is possible to distinguish the araneomorph spiders – or “true” spiders – from the mygalomorph spiders. Dangerous species for humans can be found in both groups.•Regarding “true” spiders, two kinds of envenomation are frequent, ubiquitous and potentially severe: latrodectism (neurotoxic symptomatology) due to the Widow spiders of the Latrodectus species, and loxoscelism (viscero-cutaneous symptomatology).•Regarding the mygalomorph spiders, the Australian species responsible for atraxism (neurotoxic symptomatology) are considered as the most dangerous. Most of the other mygalomorph spiders, when they bite, only provoke benign loco regional problems.•A supplementary defensive weapon exists in certain South-American species: urticating hairs which may induce severe ocular damage.
... We are, however, not aware of any report from Europe referring to bites from these species. Th is is in line with the general assumption that the frequency of spider bites is overestimated (Vetter et al. 2003). Additionally it may be possible that these alien species did not reach relevant densities or that they even did not establish in the long term. ...
... Nevertheless, one of the more consistent and dismaying aspects of the pathology known as "necrotic arachnidism" or "loxoscelism" is the substantial number of diagnoses by medical professionals that are totally unsupported by confirmatory data. In the United States, where L. reclusa has been regarded as by far the most likely source of structural Loxosceles envenomation, the principal reasons for skepticism in the absence of a victim-collected, expert-determined specimen are 1) the high incidence of reported bites outside the relatively limited native range of L. reclusa, which, contrary to a prevailing misconception, only rarely occurs in states where it is not endemic, 2) the secretive and nonaggressive behavior of this species, and 3) the numerous other possible causes of similarappearing necrotic skin lesions (Anderson 1998, Vetter and Barger 2002, Vetter et al. 2003, Vetter 2005, Swanson and Vetter 2005, Vetter and Swanson 2007, Vetter and Isbister 2008. ...
Article
Loxosceles rufescens (Dufour), a relatively cosmopolitan, synanthropic species commonly known as the Mediterranean recluse spider, inhabits numerous government buildings in the Washington, D.C. area. Like the closely related brown recluse spider (L. reclusa Gertsch and Mulaik) in the south-central United States, L. rufescens can be extremely abundant with in a structure. Unlike L. reclusa, D.C. populations of L. rufescens are essentially troglophilic, concentrated mainly in basements, foundation walls, and other man-made subterranean habitats, typically in close association with Periplaneta americana (L.) and/or Reticulitermes spp. It has not been observed either outdoors or in smaller, residential buildings. Since this spider is often misidentified as L. reclusa by entomologists who are unaware of L. rufescens' widespread distribution and potential for persistent and dense local populations, we present photographs to aid in distinguishing the adults of these two similar species.
... Loxosceles spp. are not established in Colorado and, as in many western states, bites are greatly overdiagnosed (Vetter et al. 2003). Widow spiders, primarily Latrodectus hesperus Chamberlin and Ivie, can be common in the state. ...
Article
An assessment of spider fears was made in a survey of Colorado State University students taking an introductory entomology course. Over two-thirds of the students expressed some measure of spider fear, ranging from being “a little apprehensive” to “cannot stand being in their presence.” One sixth of the students expressed highest-level fears, with females three times more likely to indicate high spider fear than males. Together, these figures indicate that spider fear levels of college students in Colorado are substantially higher than those reported from European general populations. In voluntary comments, several unspecified descriptors were used, with “creepy” and “gross” being most common, followed by “disgusting” and “scary.” The most commonly mentioned specific factor in spider fear was bites and the perceived danger of spiders. Physical features of spiders that were most commonly noted of concern were number of legs and hairiness. Several students indicated greater distress with larger spiders, but some had greater concerns with smaller spiders because of their ability to hide. Unpredictability of spiders and presence in the home, particularly the bedroom, were commonly expressed concerns. The urban legend of spider inhalation in sleep and the movie Arachnophobia appeared to be notable contributors to generation of spider fears. The need to better educate the public about spiders is discussed with some suggestions on how to achieve this.
... However, questions remain about the biology, behavior, and geographic distribution of this species. This lack of information may be the primary reason that reports of brown recluse bites are much more widespread than the spider's actual distribution (Vetter et al. 2003). ...
Article
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Members of the spider genus Loxosceles (Araneae: Sicariidae) are found throughout the world. Their venom can cause severe open necrotic lesions in humans that can take several months to heal. Bite victims may also develop systemic reactions that can be life-threatening if medical attention is delayed or unavailable. Many Loxosceles species establish large populations in human habitats, creating a threat to human health and safety. Loxosceles reclusa, the brown recluse spider, is by far the most abundant spider species in many homes throughout the south-central United States. There has been an increase in awareness of brown recluse spiders, primarily due to negative media coverage of disfiguring bites and immense, slow-healing wounds. Although the bite of L. reclusa has been identified as a cause of necrotic lesions for nearly five decades, surprisingly few studies examine the biology of these spiders, and none have examined their association with humans. Few data have been published on the killing efficacy of pesticides on L. reclusa. Although millions of dollars are spent each year to control populations of L. reclusa in homes, no studies have been conducted to test newly developed chemicals or examine the benefits of integrated pest management practices. Here, we review historical accounts of pest management for L. reclusa populations and previous laboratory studies of biology and behavior. We then discuss how current studies of urban ecology, biological control, and urban pest management contribute to the management of L. reclusa populations in human habitats.
... Conversely, necrotic lesions in general tend to be overdiagnosed as loxoscelism, but studies into the geographical distribution of this genus show that in most cases other causes are more likely. 84 Several treatments have been suggested for loxoscelism, including antivenom, corticosteroids, dapsone, antihistamines, antibiotics, analgesics, hyperbaric oxygen therapy, electric shock, and surgical excision. 26,85 However, there is little evidence to lend support to any of these treatments, 86,87 including the role of antivenom and the timing of its use, 85 partly because of the lack of knowledge about loxoscelism's pathophysiology, 5 and the paucity of clinical trials to test these therapies. ...
Article
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.
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Two species of black widow spider (BWS—Latrodectus hesperus Chamberlin & Ivie and Latrodectus variolus Walckenaer) naturally occur in Canada and are capable of causing deleterious envenomation to humans. No Canadian literature exists on the frequency of envenomations by these species or the use of antivenom in the treatment of those patients. A review of primary Canadian arachnology data was undertaken to identify BWS populations. A retrospective review of the Health Canada Special Access Program records generated epidemiology and the utilization of antivenom for BWS envenomations in Canada. The geographical distribution of BWS species is limited to along the southern Canadian border. From January 2009 to December 2015, there were five BWS envenomations that required treatment with antivenom and all cases occurred in British Columbia. An average patient age of 41 yr ± 21 SD (range 7–59) was observed, along with three of the five patients being female. The average number of vials used for treatment was 2 ± 1 SD (range 1–3). BWS Antivenin was also obtained by facilities in Alberta, Ontario, and Nova Scotia, but not used in any of these jurisdictions. Further investigation is necessary to determine the annual incidence of BWS envenomations and if treatment with BWS antivenin is required.
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El teléfono celular es un dispositivo muy utilizado por personas de todas las edades y en todas partes del mundo. Entre los estudios realizados respecto a los efectos perjudiciales de las radiaciones en el organismo humano no existe un consenso. Por ello es preciso analizar los referentes teóricos acerca de los efectos deletéreos de las radiaciones sobre el ser humano e identificar un conjunto de acciones que contribuyan a disminuir la exposición a este tipo de radiaciones. El objetivo general es dar la información al usuario sobre la exposición a la radiofrecuencia excesiva por el uso indiscriminado del celular y para advertir sobre los problemas de salud que puede producir y las consecuencias que en un futuro podría desencadenar. Las radiaciones pueden afectar al ser humano de forma negativa, sobre todo por exposición prolongada. Diversos estudios revisados indican que las radiaciones están asociadas a la aparición de alteraciones de la salud y describen que entre los mecanismos fundamentales para producir el daño en el hombre se encuentran los efectos térmicos, no térmicos y atérmicos, pero se requieren ampliar los estudios, con énfasis en los epidemiológicos, para analizar las hipótesis generadas acerca de este particular.
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Erythema migrans (EM) rashes once considered pathognomonic of Lyme disease (LD) have been reported following bites of arthropods that do not transmit LD and in areas with no LD. Also, EM rashes have been reported in association with organisms other than members of Borrelia burgdorferi sensu lato complex. Arthropod saliva has chemicals that have effects on the host and pathogen transmission. Tick saliva has protein families similar to spiders and scorpions and even substances homologous to those found in snakes and other venomous animals. Ticks "invertebrate pharmacologists" have a sophisticated arsenal of chemicals that assist in blood feeding, pathogen transmission, and suppressing host defenses. No organisms have been isolated from many EM rashes. We propose that tick salivary toxins may play a role in the causation of rashes and laboratory abnormalities in tick-borne diseases. The role of tick salivary toxins needs further exploration. Cases of Lyme-like EM rashes referred to as STARI (Southern Tick-Associated Rash Illness) following bites of the lone star tick, Amblyomma americanum, in the United States have been reported predominantly in Southeastern Missouri and a few in South Carolina, North Carolina, Georgia, and one case each in Mississippi and Long Island, New York. Although there is one report of Borrelia lonestari in a patient with a rash, biopsies of 31 cases of STARI, with cultures and PCR, failed to show a relationship. Distribution of A. americanum, whose bites are associated with STARI, now extends along the East Coast of the United States, including New Jersey, up to the Canadian border. As far as we are aware, there have been no prior reports of Lyme-like rashes in New Jersey. In this study, we present case examples of 2 Lyme-like rashes, variations of EM rashes, and a brief review of studies that suggest a role of tick salivary toxins in tick-borne diseases.
Chapter
Brown recluse spiders are known for the necrotic skin lesions they may produce. However, there is frequent misdiagnosis of brown recluse bites due to similar dermonecrotic lesions resulting from other conditions such as impetigo, decubitus ulcers, staph infections, ecthyma gangrenosum, and the like. This chapter presents facts and fables about brown recluse spiders, their bite reactions, and various treatment and control strategies.
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OBJECTIVE To dispel prevalent myths surrounding diagnosis of dermonecrotic and associated conditions supposedly resulting from bites of brown recluse, hobo, or other spiders in Canada. SOURCES OF INFORMATION Worldwide, spider bites are regularly misdiagnosed as the etiologic agents in human dermonecrosis mainly as a result of inaccurate, erroneous, or hyperbolic popular and professional literature based on inference, circumstantial evidence, inferior clinical trials, and misunderstanding of the facts regarding spider-bite envenomation. MAIN MESSAGE A working diagnosis of "spider bite" or publishing a case history should be considered only when a spider is caught in the act of,biting or otherwise reliably associated with a lesion. Accurate identification of the spider could be critical for correct diagnosis and subsequent treatment. CONCLUSION Brown recluse spiders are not found in Canada. Hobo spiders have not been reliably implicated in dermonecrosis. Worldwide, spider-bite envenomation is-an, unlikely cause of dermonecrosis. Canadian physicians should give priority consideration to other, more likely, causes.
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We analyzed the reliability and information content of 134 medical case studies on spider bites, published in 91 journal articles. Overall, we found that only 22% of these studies fulfilled the criteria for a verified spider bite. This means that the majority of such case studies cannot be attributed to a given spider species and usually not even to a spider. Their scientific value is negligible, moreover, such publications are even dangerous because they suggest incorrect conclusions. Secondly, we found that such case studies usually do not follow an obvious structure and many details on the development of symptoms, therapy and healing process are widely lacking. So even for verified spider bites, the comparability of case studies is limited. We discuss the obvious failure of a reviewing process for case studies and give recommendations how to increase the currently low information content of medical case studies on spider bites.
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Community-associated methicillin-resistant Staphylococcus aureus has rapidly risen in incidence to become not only very common, but the predominant cause of S. aureus infections in many parts of the world. This bacterium is notable for its predilection to cause infections in healthy persons and be transmitted easily from person to person. Additionally, this organism has the ability to cause severe, life-threatening infections that were previously only rarely, if ever, associated with S. aureus. Optimal methods to treat and prevent this infection are uncertain and will require extensive investigation.
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When a patient presents with a necrotic skin lesion, brown recluse spider bite is often considered as part of the differential diagnosis. Because patients are at risk for severe systemic symptoms that on rare occasion progress to death, failure to correctly diagnose a brown recluse spider bite can be catastrophic. However, bites are uncommon even in areas of the Midwest where brown recluse spiders are endemic. The medical literature regarding brown recluse spider bites is difficult to interpret because there is no gold standard diagnostic test. When a diagnosis is confirmed, often because a patient obtains a spider for identification, multiple therapeutic options are available including "RICE" therapy, dapsone, and surgical excision. New diagnostic and therapeutic strategies are needed.
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The incidence of community‐acquired methicillin‐resistant Staphylococcus aureus is rising—only one fact that PAs must consider as they re‐evaluate their approach to the patient with a subcutaneous abscess.
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Myths are an integral aspect of the psychology of human culture. They function to help explain the mysteries of the vast world and beyond, providing explanations for natural phenomena, alleviating anxiety and attempting to make sense of a complex world. Although they abound in the general population, myths also occur in science and medicine such that their development within these specialized fields of assumed fastidiously derived knowledge can sometimes expand into the general public where the myths gain great acceptance. However, some of these myths are based on incorrect information and are honed or pushed forward by the psychological tendencies of humans to want explanations for what we see. The unknown is unsettling and possibly threatening, hence, an explanation, no matter how specious, functions to fill a void. There are many psychological and medical mechanisms that generate and propagate myths and prevent their destruction. Nonetheless, by subjecting these myths to the scientific process of falsifiability, the incorrect ones can be assailed and hopefully replaced with information that is more evidence based. After a general review of the psychology of myths and how science offers a regulating influence, several examples of myths are presented from the world of spiders. These spider myths differ in their origins, how they were propagated and how they were falsified by using the scientific process. Disproving a myth is merely one step; getting the believers of the myth to rescind their line of thinking is yet another matter.
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Our aim was to assess the evolutionary history of the spider genus Loxosceles on the Canary Islands. We unravelled its present diversity within the archipelago, and investigated its origin, mode and tempo of colonization to and between the islands using a phylogenetic framework. Canary Islands, Madeira, Iberian Peninsula, North Africa, Mediterranean region, Guinea. We conducted extensive sampling across the Canary Islands, and examined the phylogenetic relationships among the Canary Island representatives of the genus Loxosceles and with regard to species from western Africa and the Mediterranean Basin. We used an evolutionary criterion (general mixed Yule coalescent) to delimit the evolutionary lineages, and applied fossil and biogeographical calibration points to estimate dates for major cladogenetic events within the Canary Islands using a Bayesian framework. Phylogenetic analyses revealed the existence of a well-supported clade formed exclusively by Canarian Loxosceles specimens, comprising seven allopatrically distributed evolutionary lineages. Major dispersal events between the islands occurred during the late Miocene. Representatives of the cosmopolitan Loxosceles rufescens were also found on the archipelago. We have revealed the existence of an overlooked endemic group of medically important spiders. The pattern of diversity of this group fits well with the general dynamic theory of oceanic island biogeography, where maximum diversity is found on islands of intermediate age. The colonization pathway of the group is compatible with a stepping-stone model. Between-islands dispersal was the major driving force for diversification in the group, but a few within-island speciation events were also inferred, such as on Gran Canaria, where the Roque Nublo volcanic event acted as a vicariant agent, promoting the split between the two Gran Canarian lineages. The recently introduced L. rufescens is cohabiting with the endemic lineages.
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Knowledge of spider bites in Central Europe derives mainly from anecdotal case presentations; therefore we aimed to collect cases systematically. From June 2011 to November 2012 we prospectively collected 17 cases of alleged spider bites, and together with two spontaneous notifications later on, our database totaled 19 cases. Among them, eight cases could be verified. The causative species were: Cheiracanthium punctorium (3), Zoropsis spinimana (2), Amaurobius ferox, Tegenaria atrica and Malthonica ferruginea (1 each). Clinical presentation was generally mild, with the exception of Cheiracanthium punctorium, and patients recovered fully without sequelae. In Switzerland, spider bites generally have a benign clinical course, which is characterised by minor effects, with rapid and complete recovery. Since only verified spider bites can be regarded as spider bites, in the case of clinically important arachnidism, the spider should be sent to an expert for identification. Our study may help to diminish spider fear and reassure people who have experienced a bite.
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The bite of the brown recluse spider, Loxosceles reclusus, can cause necrotic skin wounds. However, the evidence strongly suggests that many skin reactions are milder, that lesions attributed to bites by this quarter-sized arthropod often have other causes, and that the spider is less aggressive than commonly believed. The efficacy of various proposed treatments remains in question.
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Snake and spider bites, as well as scorpion sting envenoming, are neglected diseases affecting millions of people all over the world. Neurological complications vary according to the offending animal, and are often directly related to toxic effects of the venom, affecting the central nervous system, the neuromuscular transmission, the cardiovascular system, or the coagulation cascade. Snake bite envenoming may result in stroke or muscle paralysis. Metalloproteinases and other substances (common in vipers and colubrids) have anticoagulant or procoagulant activity, and may induce ischemic or hemorrhagic strokes. The venom of elapids is rich in neurotoxins affecting the neuromuscular transmission at either presynaptic or postsynaptic levels. The clinical picture of scorpion sting envenoming is dominated by muscle weakness associated with arterial hypertension, cardiac arrythmias, myocarditis, or pulmonary edema. These manifestations occur as the result of release of catecholamines into the bloodstream or due to direct cardiac toxicity of the venom. Cerebrovascular complications have been reported after the sting of the Indian red scorpion. Intracranial hemorrhages occur in the setting of acute increases in arterial blood pressure related to sympathetic overstimulation, and cerebral infarctions are related to either cerebral hypoperfusion, consumption coagulopathy, vasculitis, or cardiogenic brain embolism. Three main syndromes result from spider bite envenoming: latrodectism, loxoscelism, and funnel-web spider envenoming. Latrodectism is related to neurotoxins present in the venom of widow spiders. Most cases present with headache, lethargy, irritability, myalgia, tremor, fasciculation, or ataxia. Loxoscelism is caused by envenoming by spiders of the family Sicariidae. It may present with a stroke due to a severe coagulopathy. The venom of funnel-web spiders also has neurotoxins that stimulate neurotransmitter release, resulting in sensory disturbances and muscle paralysis. Proper management of the envenomed patient, including prompt transport to the hospital, correction of the hemostatic disorder, ventilatory support, and administration of antivenom, significantly reduce the risk of neurological complications which, in turn, reduce the mortality and improve the functional outcome of survivors.
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In North America, spider envenomation is perceived to be a greater threat than in actuality; however, it still is a valid source of morbidity and, very rarely, mortality. Only 2 groups (widows, recluses) are medically important on this continent. Widow bites affect the neuromuscular junction, have minor dermatologic expression, and are treated with analgesics and antivenom. Recluse bites vary from mild, self-limiting rashes to extensive dermonecrosis. Recent awareness of methicillin-resistant Staphylococcus aureus as a ubiquitous cause of skin injury that is often mistaken as attributable to recluse bites has questioned the credence of spiders being the cause of idiopathic wounds.
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Objective: To provide a comprehensive review of relevant literature regarding the brown recluse spider (BRS) and to define those criteria that must be satisfied before making a diagnosis of brown recluse envenomation. Etiology: The complex venom of the BRS contains sphingomyelinase D, which is capable of producing all the clinical signs in the human and some animal models. Diagnosis: There is no current commercially available test. In humans there are many proposed guidelines to achieve a definitive diagnosis; however, there are no established guidelines for veterinary patients. Therapy: Currently, no consensus exists for treatment of BRS envenomation other than supportive care, which includes rest, thorough cleaning of the site, ice, compression, and elevation. Prognosis: Prognosis varies based on severity of clinical signs and response to supportive care.
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Brown recluse (Loxosceles reclusa) spider bites mainly occur in the southern and Midwestern United States. The clinical manifestation of brown recluse spider bites varies from skin irritation, a small area of tissue damage to neuropathic pain, necrotic arachnidism and severe systemic reactions such as acute renal failure and even death. Treatment is controversial and nonspecific. We describe a case of extensive right lower extremity tissue necrosis and intractable neuropathic pain treated with lumbar sympathetic block in a patient with a documented brown recluse spider bite. Both his pain and tissue necrosis improved significantly with lumbar sympathetic block with local anesthetic. After a series of lumbar sympathetic blocks, his symptoms resolved and lower extremity wound healed rapidly. We discuss the benefit of sympathetic blockade not only for neuropathic pain but also possibly as a treatment for necrotic arachnidism from a brown recluse spider bite.
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To the editor,I would like to make some comments on the article by Dr Vetter on idiopathic wounds and spider bites in the November issue of the journal.1 Unfortunately, the mythology of spider bites is not confined to the United States and enjoys considerable publicity across the Pacific in Australia and New Zealand.In Australia, little evidence supports the existence of a spider that causes necrotic ulcers. Loxosceles rufescens has been introduced into a small region in South Australia, but reports of necrotic arachnidism occur in all parts of Australia, and this spider has only been implicated in 2 cases.2 The white-tail spider (Lampona spp) is the spider implicated most commonly in the development of necrotic wounds in Australia; however, only 2 confirmed bite cases are cited in the literature and these patients developed only minor ulcers.3 Other implicated spiders include the black house spider (Badumna insignis) and wolf spiders (family Lycosidae). Sac spiders occur in Australia, but unlike in other parts of the world, they have not been implicated in cases involving necrotic lesions.4Results of studies of the venoms of Australian spiders are also inconclusive and, if interpreted in the light of clinical evidence, suggest that the venoms of most Australian spiders do not contain clinically significant cytotoxic components.5,6 A recent study showed that compared with the venom of recluse spiders (L rufescens) found in South Australia, the venom of white-tail and black house spiders does not have any sphingomyelinase activity.5 This finding supports the idea that the venoms are not the cause of necrotic ulcers; however, the investigators conclude differently, based on finding sphingomyelinase activity in midgut extractions.Venom research is based on the assumption that these spiders cause necrosis in humans, but scant evidence supports this hypothesis. There are mainly case reports of suspected spider bites or cases where the spider was not caught or correctly identified. Results of larger series of confirmed spider bites do not support the existence of necrotic arachnidism in Australia.7,8,9 In 52 cases of confirmed white-tail (L cylindratalmurina group) spider bites, no necrosis or ulceration developed.9 Despite this, the diagnoses of “white-tail spider bite” and necrotic arachnidism are entrenched in Australian medical culture, and other diagnoses usually are not even entertained.Vetter refers to a case from Australia in which a skin lesion initially identified as a spider bite was eventually found to be caused by a fungal infection, sporotrichosis.10 There are other cases of misdiagnosis of necrotic arachnidism in Australia, including pyoderma gangrenosum,11Chromobacterium violaceum8 and Mycobacterium ulcerans.12 In my experience, even more common conditions are misdiagnosed, including Herpes zoster, candidiasis, staphylococcal infections, and skin reactions to arthropod bites (usually bullous reactions). Although secondary infections may result from spider bites, this occurrence appears to be uncommon in a series of 371 confirmed spider bites (unpublished data, 2000).I support the author in urging the medical community to investigate necrotic wounds properly and not simply implicate spiders as the cause of ulceration. With no history of spider bite, the diagnosis of necrotic arachnidism should be at the end of a long list of important differential diagnoses of necrotic ulcers. A good history and physical examination may quickly reveal common causes. Investigations should include wound swabs for microbiologic analysis, and for persistent necrotic lesions (over 3 to 4 weeks), a skin biopsy specimen should be sent for histopathologic assessment and appropriate microbiologic cultures (eg, fungal). In most cases, a correct diagnosis will allow the start of appropriate treatment.
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Envenomations by the brown recluse spider have been reported throughout North America, despite the fact that the spider's range is limited to the South and central Midwest of the United States. Several of these medical reports have originated from regions of nonendemicity where the spider has never or rarely been documented and brown recluse spider populations are unknown. In most of these reports, no spider is positively identified in association with the dermonecrotic wound, and diagnosis has been based on clinical examination findings. Considering the extreme rarity of brown recluse spiders in areas of nonendemicity, the diagnosis of a presumptive bite is a misdiagnosis that reinforces the assumption that brown recluse spiders are common local etiologic agents of necrosis. There are many medical conditions of diverse origin that have been misdiagnosed as brown recluse spider bites, some of which can be fatal or debilitating. Physicians' awareness of these conditions will increase diagnostic accuracy in areas of North America where bites from brown recluse spiders are improbable
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Spider bite is a subject of much medical mythology with prevalent fears that spiders cause severe envenoming, with neurotoxic effects or necrotic ulcers. Clinical experience and small studies suggest otherwise, but this has not been confirmed by prospective studies of bites by identified spiders. To describe the clinical effects of bites by accurately identified spiders, and determine whether early clinical features and circumstances can predict spider type. Prospective follow-up study. Patients were recruited from admissions to two emergency departments (n=48) and referrals from three state poison information centres (n=1426), over 27 months. Overall, there were 750 people with definite spider bites where the spiders were immediately collected and expertly identified. Significant effects occurred in 44 bites (6%), including 37 (of 56) redback spider bites (Latrodectus hasselti) with significant pain lasting >24 h. Of these, only 6 (11%) received antivenom. One severe neurotoxic envenoming by an Australian funnelweb spider required antivenom. No definite spider bites resulted in necrotic ulcers (0%, 99%CI 0-0.7%). There were no early allergic reactions and secondary infection occurred in seven cases (0.9%, 95%CI 0.4-1.9%). Circumstances and early clinical effects were strongly associated with taxonomic spider identification, with positive predictive values >0.95 for common groups of spiders. Australian spider bite caused minor effects in most cases and is unlikely to cause necrotic ulcers, allergic reactions or infection. Redback spider bite (widow spider) caused prolonged pain, and antivenom could have been used more frequently. The circumstances and early clinical features of spider bites may allow early appropriate advice and treatment of spider bite without taxonomic identification.
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Pyoderma gangrenosum is a diagnosis of exclusion, and the misdiagnosis of pyoderma gangrenosum can result in substantial complications in patients who have other causes of severe cutaneous ulceration. We reviewed the charts of 240 patients with a diagnosis of pyoderma gangrenosum who were evaluated at our institution from 1975 through 2000, including 157 consecutive patients treated for presumed pyoderma gangrenosum from 1984 through 1992. We also reviewed the English-language literature. Ninety-five patients (49 from our institution and 46 described in the literature) had skin ulcers with a clinical resemblance to pyoderma gangrenosum. The final diagnoses were vascular occlusive or venous disease, vasculitis, cancer, primary infection, drug-induced or exogenous tissue injury, and other inflammatory disorders. Of the 95 patients studied, 64 had been treated for pyoderma gangrenosum for a median of 10 months (range, 3 to 180). These 64 included 15 of the 157 consecutive patients treated for pyoderma gangrenosum at our institution (10 percent). Of the ulcers in the 64 patients treated for pyoderma gangrenosum, it was clear that those in 23 patients (36 percent) did not respond to treatment directed at pyoderma gangrenosum, those in 8 (12 percent) were exacerbated by such treatment, and those in 15 (23 percent) improved with such treatment. The misdiagnosis of pyoderma gangrenosum is not uncommon and exposes patients to risks associated with its treatment. A thorough evaluation is required in all patients suspected of having pyoderma gangrenosum in order to rule out alternative diagnoses.
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During a 6-mo period, 2,055 brown recluse spiders, Loxosceles reclusa Gertsch and Mulaik, were collected in a 19th-century-built, currently occupied home in Lenexa, KS. We conservatively estimate that at least 400 of these spiders were large enough to cause envenomation. Additional collections from more typically infested homes in Missouri and Oklahoma in 2001 yielded 45 and 30 brown recluse spiders, respectively. Despite these infestations, no envenomations of the inhabitants of these three homes occurred. Considering the levels of infestations with no bites in the homes presented here, nonendemic areas in the United States, which typically lack recluse spider populations and have had zero to few verified specimens of the spider, do not have sufficient numbers of brown recluse spiders to make envenomation a likely scenario. Despite this, physicians from nonendemic recluse areas often diagnose brown recluse bites which, therefore, are unlikely to be correct.
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Loxoscelism or necrotic arachnidism are the terms used to describe the effects of the brown recluse spider bite. Over recent years, there has been a steady increase in the number of reported brown recluse spider bites. It is not clear whether this represents an expanded range of the spider's habitat or greater physician awareness. Although most commonly found in the warm, south central region of the United States, Loxosceles reclusa can be a cause of necrotic arachnidism in northern urban settings. Therefore, the diagnosis should also be considered in these areas. This article discusses three cases of suspected brown recluse spider bites referred to a Chicago-based poison control center and briefly reviews the literature regarding the diagnosis, clinical presentation and treatment of loxoscelism.
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A population of 2,366 primary care physicians in South Carolina was surveyed by mail to estimate the number of cases of insect morbidity treated in 1990. A response rate of 42.3 percent was obtained. Cases reported totaled 414 for Rocky Mountain spotted fever, 334 for Lyme disease, 143 black widow and 478 brown recluse spider bites and 4,975 fire ant stings. These are counts of cases from a mail survey, not from a research-based study. Five deaths were also reported; two for Rocky Mountain spotted fever, two due to black widow spider bites and one fire ant anaphylaxis.
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A random survey of 2,189 houses in rural and urban sections of central Chile was done to learn the frequency with which they were infested with Loxosceles laeta, a poisonous spider that causes severe envenomation of man. More urban (40.6%) than rural (24.4%) houses were infested, but a higher density of spiders was found in rural (11.9) than in urban (3.9) houses. Of the 5,449 spiders collected, 20.4% were immature; a ratio of one male to eight females was found among the adults. The high proportion of infested houses strengthens the assumption that this species is essentially domestic and explains why its envenomation of man occurs principally indoors. The presence of these spiders is related to the characteristics of the dwellings and to the cultural level of their inhabitants. In the rural areas the low level of education and the larger size of dwellings favor the proliferation of the spiders and their persistence, causing a higher density of spiders per house than in urban houses. On the other hand, rural houses are scattered, limiting the migration of spiders to other houses. In contrast, migration from one house to another is common in urban communities and explains the higher percentage of houses infested. It is possible that the high proportion of immature spiders, and the sex ratio observed in adults, may be due to the methods employed in collection. Despite the high frequency and density of spiders in houses, the retiring nature of L. laeta reduces the hazard of poisoning in houses infested by these spiders.
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A facile and quantitative assay for measuring the activity of sphingomyelinase D in recluse spider venom has been developed using L-alpha-[palmitoyl-1-14C]lysophosphatidylcholine as substrate. This assay avoids the problem of substrate insolubility that occurs when sphingomyelin and other insoluble lipids are used as substrates. This assay has been employed in gel filtration and isoelectric focusing isolation techniques to purify sphingomyelinase D from spider venom. The purified sphingomyelinase exhibits four active enzyme forms in isoelectric focusing with pI values of 8.7, 8.4, 8.2, and 7.8. Each active form when examined in SDS-polyacrylamide gel electrophoresis gave an estimated molecular weight of 32 000. The four active enzyme forms were immunologically cross-reactive with each other as demonstrated with radioimmune assays using an antiserum developed to one of the active forms. Each active form hydrolysed sphingomyelin to release choline and produce N-acylsphingosine phosphate. One of the active enzyme forms was characterized further in dermonecrosis and platelet aggregation measurements. This purified sphingomyelinase D was identified as a poisonous toxin that can developed typical dermonecrotic spider lesions when injected into experimental animals at levels expected to be delivered in a normal bite. Furthermore, the purified toxin acts to aggregate human blood platelets. The toxin-induced platelet aggregation has been related to serotonin release as aggregation occurs, and it has been shown to be inhibited by EDTA over the range of 0.6 yo 3.0 mM EDTA. It is suggested that spider-induced dermonecrosis could result in part from platelet aggregation at and near the site of envenomation.
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This is the first report of clinically significant bites by the grass spider (Agelenopsis aperta). Two cases of envenomation in southern California are presented. In the more serious case, a child exhibited several envenomation symptoms. Although this spider may be generally innocuous, it should be considered as a creature of occasional medical importance. Many skin lesions are attributed to spider bites despite insufficient incriminating evidence, and bites that are clinically significant may often erroneously be attributed to the brown recluse spider. Misidentification can lead to undue anxiety in a patient's family.
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Spiders, especially brown recluses (Loxosceles reclusa) (figure 1), are frequently incriminated as causative agents in idiopathic wounds, even though diagnoses are usually made solely on the basis of dermatologic symptoms. Rarely is a spider seen inflicting the wound or captured while biting, and it is difficult to either prove or disprove spider participation in the event. The biologic distribution of the brown recluse and related recluse species indicates that many diagnoses made on cases occurring in the western United States are incorrect.1 Figure 1 Dorsal view of the brown recluse spider, Loxosceles reclusa. The most consistent diagnostic feature for identification is the pattern of 6 eyes, grouped in pairs, with 1 anterior pair and 2 lateral pairs (most spiders have 8 eyes in 2 rows of 4). Although ... SOURCES OF INFORMATION Because of my research interests in spider identification and medically important spiders, I have been avidly studying recluse spiders and their occurrence in the western United States. My experience is greatest in California, but the information presented here is pertinent to northern and western states as well. In almost a decade of research, I have found verification of fewer than 10 brown recluse specimens in California in more than 40 years of records. Sources include medical and arachnologic literature and correspondence with scores of arachnologists, county entomologists, vector control personnel, and the California Department of Food and Agriculture, which handles all exotic pest identifications in the state. Most verified specimens were individuals intercepted from facilities receiving goods from out of state. There are no populations of brown recluses in California.
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Figure 1. A seven-month-old male infant was hospitalized with a two-day history of swelling of the left arm and a weeping lesion at the left elbow (Panel A). The patient was afebrile but had a 2-cm open sore, with surrounding erythema and induration, that oozed clear yellow fluid. There was nontender swelling and erythema of the entire arm. The white-cell count was 28,100 per cubic millimeter. Incision and drainage of the lesion produced 10 ml of dark red fluid. A coronal, T1-weighted sequence from a magnetic resonance imaging study (Panel B) demonstrated diffuse, severe edema of the subcutaneous tissues extending . . .
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We report a case of Lyme disease with clinical features resembling those described from brown recluse spider bites. The most striking manifestation was a necrotic skin wound. Brown recluse spider bites may be overdiagnosed in some geographic regions. Tick bite and infection with Borrelia burgdorferi should be considered in the differential diagnosis of necrotic arachnidism in regions endemic for Lyme disease. [Osterhoudt KC, Zaoutis T, Zorc JJ. Lyme disease masquerading as brown recluse spider bite. Ann Emerg Med. May 2002;39:558-561.]
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[Vetter RS, Bush SP. The diagnosis of brown recluse spider bite is overused for dermonecrotic wounds of uncertain etiology. Ann Emerg Med. May 2002;39:544-546.]
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Clinical toxinology suffers from a long history of poor data collection. A 20-year review of MEDLINE illustrates the lack of randomized controlled trials and prospective studies in clinical toxinology. Mythology surrounds bites and stings, resulting from the general fear of many creatures such as spiders, which has not been disproved by appropriate well-designed studies. The current focus on necrotic arachnidism in many parts of the world is a good example. Previously, most studies have been retrospective, bites and stings have not been confirmed, and creatures have not been kept or have been incorrectly identified. Prospective observational studies of confirmed bites with correct identification of the creature are required in clinical toxinology. This requires a collaboration between those who can correctly identify the animals (biologists/taxonomists) and those involved in the clinical management (poison information services, emergency departments, and toxicology services). Prospective collection of data pertaining to the circumstances and effects of the bites is essential. Routine follow-up is required to identify delayed effects and the duration of immediate effects. Analysis of databases created from prospective studies will not only answer questions about the effects of different species, but will ultimately allow the development of evidence-based methods to identify animals based on the circumstances and effects of bites, rather than requiring formal identification of the culprit.
A confusion of spiders
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Platelet aggregation and sphingomyelinase D activity of a purified toxin from the venom of Loxosceles reclusa
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