Distribution and medical aspects of Loxosceles rufescens, one of the most invasive spiders of the world (Araneae: Sicariidae)

Conservative Reconstruction of the Lower Limb with a Bilayer Porous Collagen Matrix after a Spider Bite

ABSTRACT

Brown recluse spider bites may cause symptoms ranging from local cutaneous reactions to systemic visceral loxoscelism. Most bites are self-limiting, but some can lead to necrotic ulcerations with severe complications and soft tissue defects. Necrotizing ulcers are uncommon and have various clinical presentations, so no standard treatment exists. A 68-year-old man required medical attention after getting a spider bite while traveling in Tanzania. After returning to Italy, the patient presented with a posterior lower limb black papule, local edema, and fever. The lesion quickly ulcerated with an eschar. Medical history and symptoms suggested a brown recluse spider bite. Ulcer management was conservative, with careful surgical debridement and a two-step reconstruction using a split-thickness skin graft and a bilayer porous collagen matrix. Treatment resulted in functional recovery and acceptable aesthetics.

Introduced Spiders in Panama: Species Distributions and New Records

Biological invasions occur when organisms are moved from their native range and introduced into new areas, where they can spread and become a potential risk for native organisms. Invasive species are well recorded for vertebrates, plants and a number of invertebrates. A taxa for which there is a lack of information in some countries are arachnids, and this is the case of reports on introduced species in Panama. Here, we report the first list of introduced spider species in the country as a result of reviewing scientific literature, online databases, museum collections and carrying out field collections. We report six new introduced species out of a total of 31 species, belonging to 10 families and 25 genera. A large proportion of these species originated from Asia. Moreover, most of the species, with historic data available, have expanded their distribution in the country. We also present a list of species that might be already present in the country or may be introduced in the future. Our work highlights the capability of spiders to invade and spread into new territories. Therefore, monitoring policies and control strategies should also consider them as potential risk for local ecosystems.

Phylogenetics and species delimitation of the recluse spider, Loxosceles rufescens (Araneae: Sicariidae) populations invading Bangkok, Thailand

The Mediterranean recluse spider, Loxosceles rufescens, has been discovered for the first time inhabiting human dwellings in Bangkok, Thailand. Expeditions across 39 localities revealed five establishments with L. rufescens populations. The highest density was recorded in a storage house on Yaowarat Road, located in the heart of Bangkok's Chinatown, where 315 individuals were found, including adults, juveniles, and spiderlings. This medically significant spider's presence in such a densely populated urban area raises concerns about potential envenomation risks. Thirteen specimens of L. rufescens were extracted for DNA and sequenced for molecular phylogenetic analyses. COI and ITS2 markers were used to investigate relationships within L. rufescens and across available Loxosceles species sequences. Results indicate COI is superior for resolving species-level genetic clusters compared to ITS2. Surprisingly, L. rufescens individuals from the same house were found in significantly distant COI lineages, suggesting mtDNA may not be suitable for studying intra-specific phylogeography in this case. Species delimitation methods ABGD and ASAP demonstrated promising results for both COI and ITS2, while bPTP and GMYC tended to overestimate species numbers. ITS2 exhibited high sequence similarity in L. rufescens, suggesting potential utility as a barcoding marker for identification of this globally distributed species. Genetic distance analyses revealed a potential barcoding gap (K2P) of 8-9 % for COI and <2 % for ITS2 in Loxosceles. This study contributes valuable sequence data for the medically important genus Loxosceles and highlights the need for integrative approaches in understanding its evolution and spread. The findings have important implications for pest management strategies and public health in urban environments.

IL, Duran CFD, Cammayo MFKM, Alviola MS, Mercado SMQ, Osio CAL, Eusebio OL, Lucañas CC, Barrion AT. Integrative taxonomy reveals first record of Loxoscelesrufescens (Dufour, 1820) (Araneae, Sicariidae) in the Philippines

Background

The spider family Sicariidae Keyserling, 1880 represented by the synanthropic Mediterranean recluse spider, Loxoscelesrufescens (Dufour, 1820), is reported in the Philippines for the first time, based on morphological and molecular data. The introduced spider was observed in a small cave (Kamantigue Cave) in Lobo, Batangas Province. Considering the medical importance of this spider, the proximity of its habitat to human habitation and tourist sites poses a potential public health concern.

New information

This study reports on the first record of the family Sicariidae in the Philippines and the fourth recorded occurrence of L.rufescens in Southeast Asia.

A Brief Overview of the Toxic Sphingomyelinase Ds of Brown Recluse Spider Venom and Other Organisms and Simple Methods To Detect Production of Its Signature Cyclic Ceramide Phosphate

A special category of phospholipase D (PLD) in the venom of the brown recluse spider (Loxosceles reclusa) and several other sicariid spiders accounts for the dermonecrosis and many of the other clinical symptoms of envenomation. Related proteins are produced by other organisms, including fungi and bacteria. These PLDs are often referred to as sphingomyelinase Ds (SMase Ds) because they cleave sphingomyelin (SM) to choline and "ceramide phosphate." The lipid product has actually been found to be a novel sphingolipid: ceramide 1,3-cyclic phosphate (Cer1,3P). Since there are no effective treatments for the injury induced by the bites of these spiders, SMase D/PLDs are attractive targets for therapeutic intervention, and some of their features will be described in this minireview. In addition, two simple methods are described for detecting the characteristic SMase D activity using a fluorescent SM analog, (N-[12-[(7-nitro-2-1,3-benzoxadiazol-4-yl)amino]dodecanoyl]-SM (C12-NBD-SM), that is cleaved to C12-NBD-Cer1,3P, which is easily separated from other potential metabolites by thin-layer chromatography and visualized under UV light. Besides confirming that C12-NBD-Cer1,3P is the only product detected upon incubation of C12-NBD-SM with brown recluse spider venom, the method was also able to detect for the first time very low levels of activity in venom from another spider, Kukulcania hibernalis The simplicity of the methods makes it relatively easy to determine this signature activity of SMase D/PLD. SIGNIFICANCE STATEMENT: The sphingomyelinase D/phospholipase D that are present in the venom of the brown recluse spider and other sources cause considerable human injury, but detection of the novel sphingolipid product, ceramide 1,3-cyclic phosphate, is not easy by previously published methods. This minireview describes simple methods for detection of this activity that will be useful for studies of its occurrence in spider venoms and other biological samples, perhaps including lesions from suspected spider bites and infections.

Effect of animal venom toxins on the main links of the homeostasis of mammals (Review)

The human body is affected by environmental factors. The dynamic balance between the organism and its environment results from the influence of natural, anthropogenic and social aspects. The factors of exogenous origin determine development of adaptive changes. The present article summarises the mechanisms of animal venom toxins and homeostasis disruption in the body of mammals. The mechanisms underlying pathological changes are associated with shifts in biochemical reactions. Components of the immune, nervous and endocrine systems are key in the host defense and adaptation processes in response to venom by triggering signalling pathways (PI3kinase pathway, arachidonic acid cascade). Animal venom toxins initiate the development of inflammatory processes, the synthesis of pro-inflammatory mediators (cytokines), ROS, proteolytic enzymes, activate the migration of leukocytes and macrophages. Keratinocytes and endothelial cells act as protective barriers under the action of animal venom toxins on the body of mammals. In addition, the formation of pores in cell membranes, structural changes in cell ion channels are characteristic of the action of animal venom toxins.

Impact of antivenom administration on the evolution of cutaneous lesions in loxoscelism: A prospective observational study

BACKGROUND

Spiders of the genus Loxosceles are distributed throughout tropical and temperate regions worldwide. Loxosceles spp. bites may evolve to necrosis, with or without intravascular hemolysis. There is no consensus regarding the best treatment to prevent necrosis. The objective of this study was to evaluate the factors associated with the development of necrosis and the impact that antivenom administration has on the evolution of cutaneous loxoscelism.

METHODOLOGY/PRINCIPAL FINDINGS

This was a prospective observational study carried out at a referral center for envenoming. Over a 6-year period, we included 146 patients with a presumptive or definitive diagnosis of loxoscelism. Depending on the symptom severity, a polyvalent anti-arachnid antivenom was administered or not-in 74 cases (50.7%) and 72 cases (49.3%), respectively. Cutaneous and systemic manifestations were assessed at admission and weekly thereafter. Adverse reactions to the antivenom were also evaluated. Cutaneous loxoscelism was observed in 141 cases (96.6%), and the spider was identified in 29 (19.9%). The mean time from bite to antivenom administration was 41.6 ± 27.4 h. After discharge, 130 patients (90.9%) were treated with corticosteroids, antihistamines and analgesics being prescribed as needed. The probability of developing necrosis was significantly lower among the patients who were admitted earlier, as well as among those who received antivenom (p = 0.0245). Among the 74 patients receiving antivenom, early and delayed adverse reactions occurred in seven (9.5%) and four (5.4%), respectively. Local infection was observed only in three (2.3%) of the 128 patients for whom that information was available.

CONCLUSIONS/SIGNIFICANCE

Necrosis after a Loxosceles sp. bite appears to more common when hospital admission is delayed or when antivenom is not administered. In addition, the administration of a polyvalent anti-arachnid antivenom appears to be safe, with a relatively low rate of adverse reactions.

Suspected Brown Recluse Spider Envenomation: Missed Diagnosis and Delayed Treatment of Loxoscelism: A Case Report

CASE

We report the case of a previously healthy 51-year-old man who presented to our hospital after worsening clinical appearance of his left ring finger, despite antibiotics and previous surgical drainage for suspected abscess at an outside institution 3 weeks ago. He was admitted to our hospital for surgical debridement and decompression. After suspicion of cutaneous loxoscelism based on the clinical record and corticosteroid administration, the patient presented a favorable evolution.

CONCLUSION

Cutaneous loxoscelism caused by a spider bite is present in Europe, mainly in the Mediterranean area, and should be considered in cases of skin infections which do not respond to antibiotics.

Worldwide Web: High Venom Potency and Ability to Optimize Venom Usage Make the Globally Invasive Noble False Widow Spider Steatoda nobilis (Thorell, 1875) (Theridiidae) Highly Competitive against Native European Spiders Sharing the Same Habitats

Venom compositions include complex mixtures of toxic proteins that evolved to immobilize/dissuade organisms by disrupting biological functions. Venom production is metabolically expensive, and parsimonious use is expected, as suggested by the venom optimisation hypothesis. The decision-making capacity to regulate venom usage has never been demonstrated for the globally invasive Noble false widow Steatoda nobilis (Thorell, 1875) (Theridiidae). Here, we investigated variations of venom quantities available in a wild population of S. nobilis and prey choice depending on venom availability. To partially determine their competitiveness, we compared their attack rate success, median effective dose (ED₅₀) and lethal dose (LD₅₀), with four sympatric synanthropic species: the lace webbed spider Amaurobius similis, the giant house spider Eratigena atrica, the missing sector orb-weaver Zygiella x-notata, and the cellar spider Pholcus phalangioides. We show that S. nobilis regulates its venom usage based on availability, and its venom is up to 230-fold (0.56 mg/kg) more potent than native spiders. The high potency of S. nobilis venom and its ability to optimize its usage make this species highly competitive against native European spiders sharing the same habitats.

An unexpected turn of events: A rare case of Acquired Haemophilia A after a violin spider bite

We report an interesting clinical case of Acquired Haemophilia A (AHA) after a probable Loxosceles rufescens spider bite in a 73- year-old woman, admitted to an Emergency Department (ED) of Central Italy during April 2019. AHA is a rare disease, whose acute clinical manifestations are not widely known by most ED physicians; its prompt recognition and treatment are crucial to avoid fatal bleeding. In particular, the development of AHA after a violin spider bite (another rare and poorly characterized clinical condition) has never been described. Therefore, our case report could provide useful insight into the understanding and treatment of such unusual and possibly life-threatening conditions.

Spider bites in France: Epidaemiology of cases occurring in 10 years in metropolitan France

Spiders are often wrongly designated as responsible for cutaneous eruptions. We aim to describe spider bites and the spider species implicated in metropolitan France. A retrospective observational study was conducted for all reported cases of spider bites from 2007 to 2018 extracted from the French Poison Control Centers (PCCs) information system, after exclusion of non-native spiders. We described identification of the spider, level of certainty of the bite, symptoms and severity of cases. 1194 cases of spider bites met the inclusion criteria. The average age of the patients was 36.9 ± 19.8 years. Identification of the species or at least that a spider was implicated was only possible in 346 cases (29.0%). Loxosceles were involved in 53 cases (4.4%), Latrodectus in 46 cases (3.9%) and Cheiracanthium in 35 cases (2.9%). In one third of cases, the involved spider was not known to be present where the bite occurred. Where most of the patients (n = 1111, 93%) reported at least one cutaneous symptom, most of the symptoms were neurological. The bite was considered proven in only 242 cases (20%). Despite the efforts of arachnologists to educate the public, the fear of spiders is still alive in France, where spider bite is rare with low severity and often unproven.

The Mediterranean species of genus Loxosceles Heineken &amp; Lowe, 1832 (Araneae: Sicariidae): Loxosceles imazighen sp. n. from Morocco and first description of the female of L. mrazig Ribera &amp; Planas, 2009 from Tunisia

The aim of this paper is to describe a new species of the genus Loxosceles Heineken & Lowe, 1832 from Morocco, Loxosceles imazighen sp. n., and to describe for the first time a female of Loxoxceles mrazig Ribera & Planas, 2009 from Tunisia. Both species live in xeric and desert environments and are located in southern Atlas Range. Molecular phylogenetic analyses, using mitochondrial (cox1, 16S) and nuclear (H3, 28S) markers, revel that these species are closely related and that they constitute a separate evolutionary lineage of L. rufescens (Dufour, 1820) and of the set of endemic species of the Canary Islands. L. imazighen sp. n. differs from L. mrazig, the closest species morphologically and geographically, in the shapes and proportions of the male palpal tibia and the shapes and dispositions of the female seminal receptacles. In addition, L. mrazig females show morphological variability in their genitalia, mainly in the inner and outer lobes. Although that variability cannot be associated with different populations, since it also appears within individual populations, and is not related to genetic or geographic distances.  

Cutaneous mammary loxoscelism: An unknown cause of breast inflammation: A case report and review of the literature

Envenomation due to a Loxosceles spider bite is a rare event in France and no case concerning the breast has yet been reported. We report the case of a 48-year-old woman who presented at Saint-Etienne University Hospital with a pulsatile pain in her left breast two days after feeling a fleeting bite. An abscess was diagnosed and antibiotics were prescribed. A few days later, a necrotic zone appeared around the areola and 75 percent of the surrounding skin was inflamed. The patient reported a persistent fever and a burning pain in her breast. Loxoscelism was finally concluded and surgical debridement was undertaken, followed by supervised wound therapy and local skin care. Complete healing was achieved after 4 weeks of treatment. The diagnosis of loxoscelism is generally presumptive, as the bite is usually painless and the spider rarely captured. Its diagnosis should be considered when an abscess responds poorly to antibiotics.

Uncommon differential diagnosis of a breast ulcer: a case study

INTRODUCTION

Spider bites are common worldwide. Frequently symptoms resolve without any adverse outcome, but in rare cases the bite can cause severe morbidity. The most typical presentation of Mediterranean recluse spider (Loxosceles Rufescens) bite is a dermatonecrotic lesion of the skin (skin loxoscelism). When the only manifestation of a spider bite is an ulcerated skin lesion, clinical suspicion and differential diagnosis strongly depend on its site. We present the case of an ulcerated wound of the breast, diagnosed as a Mediterranean recluse spider bite.

CASE PRESENTATION

A 79-year-old woman presented a 10cm-wide soft tissue ulceration of her left breast. At first, the diagnostic hypothesis of an ulcerated cancer was ruled out. Two family members revealed a recent history of Mediterranean recluse spider bite and the same clinical diagnosis was made for our patient. A wide excision was performed, with complete resolution of symptoms.

DISCUSSION

No specific diagnostic criteria for spider bites are available. Diagnosis is usually clinical. Skin loxoscelism could be easily mistaken for cellulitis, various types of skin infections, cutaneous anthrax, vasculitis, scorpion sting, pyoderma gangrenosum, erythema migrans of Lyme disease or prurigo nodularis. A thorough anamnestic interview is fundamental to raise the diagnostic hypothesis. When possible, a biopsy is recommended and it is extremely important when the ulcer can mimic a cancer, as is the case in breast tissue.

CONCLUSION

We recommend a wide excision of the wound after failure of conservative treatment, in order to obtain local control and to perform histological examination on a more representative specimen.

'Burning Violin': The Medically Important Spider Genus Loxosceles (Araneae: Sicariidae) in Iran, Turkmenistan, and Afghanistan, With Two New Species

The taxonomic status of the medically important spider genus Loxosceles Heineken et Lowe, 1832 (Sicariidae) in Iran, Turkmenistan, and Afghanistan is revised. Two species are described as new to science: Loxosceles coheni sp. n. (♂♀, southwestern Iran) and Loxosceles turanensis sp. n. (♂♀, southern Turkmenistan and eastern Iran). Additionally, Loxosceles alicea Gertsch, 1967 syn. n. (♀, Peru) is synonymized with Loxosceles rufescens (Dufour, 1820). The local distribution of all treated species is mapped (including several new records), and reported cases of loxoscelism from this region are briefly reviewed.

New faunistic and taxonomic notes on the Haplogyne and Cribellate spiders (Araneae: Dictynidae, Dysderidae, Eresidae, Filistatidae, Sicariidae) from three Balkan countries

In this paper, we report for the first time two spider species for Albania, four for Bulgaria and two for Greece: Altella lucida (Simon, 1874) (Bulgaria), Eresus moravicus Rezác, 2008 (Bulgaria and Greece), Filistata insidiatrix (Forsskål, 1775) (Albania), Harpactea samuili Lazarov, 2006 (Greece), Loxosceles rufescens (Dufour, 1820) (Albania), Pritha parva Legittimo, Simeon, Di Pompeo et Kulczycki, 2017 (Bulgaria) and Pritha vestita (Simon, 1873) (Bulgaria). The recently described species P. parva is the first report for the Balkan Peninsula, while P. vestita is the first record for mainland Europe. Their congener Pritha nana (Simon, 1868) is removed from the Bulgarian checklist of spiders (misidentification). As a result of our report, the number of spider species increases to 571, 1049 and 1183 in Albania, Bulgaria and Greece, respectively.

Spider bites of medical significance in the Mediterranean area: misdiagnosis, clinical features and management

Despite the disrepute spiders have had for centuries, their bite is a rare occurrence. In the Mediterranean area, only two of the numerous known species are considered of medical significance: Latrodectus tredecimguttatus and Loxosceles rufescens. Spider bites have no pathognomonic signs or symptoms, therefore most diagnoses are presumptive; a spider bite can only be diagnosed when a spider (seen at the time of the bite) is collected and identified by an expert, since most physicians and patients are unable to recognize a certain spider species or distinguish spiders from other arthropods. Skin lesions of uncertain etiology are too often attributed to spider bites. In most cases, these are actually skin and soft-tissue infections, allergic reactions, dermatoses etc. Misdiagnosing a wound as a spider bite can lead to delays in appropriate care, cause adverse or even fatal outcomes and have medical-legal implications. Concerningly, misinformation on spider bites also affects the medical literature and it appears there is lack of awareness on current therapeutic indications for verified bites.

A multidiversity approach to investigate the impact of mining exploitation on spider diversity in the abandoned mine district of Montevecchio-Ingurtosu (Sardinia, Italy)

The impact of mining activities on spider (Araneae) diversity and assemblages was studied in two abandoned mine sites in Sardinia (Italy), where mining activities started in the middle of the nineteenth century and closed down over a century later. Spider community composition was analysed in dumps, undisturbed forests and scrublands which represent the natural chronosequence following the abandonment of the mining district. The identification of spiders was performed at the lowest taxonomic level possible and differences in abundance, species richness (SR), and functional diversity (FD) were analysed. Nonmetric multidimensional scaling (NMDS) and a permutated multivariate analysis of variance (PERMANOVA) routine were conducted to evaluate the relationships of spider assemblages with land cover, and the indicator species analysis was performed to identify the typifying species. During the entire sampling period, 2312 spiders were captured, and approximately 80% of the total were identified at the species level (79 spider species belonging to 28 different families). No differences in abundance and SR were found, whereas FD, which showed the highest values in forests, significantly differed among sites. A distinct separation among assemblages and a significant effect of the land use on spider assemblages were found (PERMANOVA, R² = 0.59, p < 0.001). Twelve species were selected as indicator species. Our results underlined the possibility to consider ground-dwelling spiders as a valuable target group for biomonitoring programmes supporting projects of near-natural restoration and/or technical reclamation of mining sites.

Local Dermonecrosis with Generalized Urticaria Probably Due to Loxosceles rufescens Bite

BACKGROUND: The spiders of the Loxosceles genus, commonly denoted as “brown spiders” or “Mediterranean recluse” or “brown recluse,” belong to the spider family Sicariidae, suborder Labidognatha, order Araneida, class Arachnida, and phylum Arthropoda. This spider is widespread in Africa and South/Central America, but it is also distributed in North America, in the West Indies, in the Mediterranean Europe, and in China. CASE REPORT: Here, we report the case of a severe dermonecrotic loxoscelism identified in Southern Italy, probably due to the bite of Loxosceles rufescens. The patient was a women admitted at hospital ER because of a little skin erythema that evolved toward a severe necrosis and ulceration within 20 days. After clinical and laboratory data excluded other local and systemic diseases, she was treated with a systemic and local therapy using corticosteroids and antibiotics with the diagnosis of loxoscelism. The healing from the local skin lesion occurred within 2 months, but the local pain, weakness, and discomfort lasted for a long time. CONCLUSION: It is the fisrt time that a possible case of systemic loxoscelism with skin generalized urticaria is reported in Italy.

Biotechnological potential of Phospholipase D for Loxosceles antivenom development

Loxoscelism is one of the most important forms of araneism in South America. The Health Authorities from countries with the highest incidence and longer history in registering loxoscelism cases indicate that specific antivenom should be administered during the first hours after the accident, especially in the presence or at risk of the most severe clinical outcome. Current antivenoms are based on immunoglobulins or their fragments, obtained from plasma of hyperimmunized horses. Antivenom has been produced using the same traditional techniques for more than 120 years. Although the whole composition of the spider venom remains unknown, the discovery and biotechnological production of the phospholipase D enzymes represented a milestone for the knowledge of the physiopathology of envenomation and for the introduction of new innovative tools in antivenom production. The fact that this protein is a principal toxin of the venom opens the possibility of replacing the use of whole venom as an immunogen, an attractive alternative considering the laborious techniques and low yields associated with venom extraction. This challenge warrants technological innovation to facilitate production and obtain more effective antidotes. In this review, we compile the reported studies, examining the advances in the expression and application of phospholipase D as a new immunogen and how the new biotechnological tools have introduced some degree of innovation in this field.

Clinical aspects, diagnosis and management of Loxosceles spider envenomation: literature and case review

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.

Under an integrative taxonomic approach: the description of a new species of the genus Loxosceles (Araneae, Sicariidae) from Mexico City

A new species of the spider genus Loxosceles Heineken & Lowe, 1832, Loxosceles tenochtitlan Valdez-Mondragón & Navarro-Rodríguez, sp. nov., is described based on adult male and female specimens from the states of Mexico City, Estado de Mexico and Tlaxcala. Integrative taxonomy including traditional morphology, geometric and lineal morphology, and molecules (DNA barcodes of cytochrome c oxidase subunit 1 (CO1) and internal transcribed spacer 2 (ITS2)), were used as evidence to delimit the new species. Four methods were used for molecular analyses and species delimitation: 1) corrected p-distances under neighbor joining (NJ), 2) automatic barcode gap discovery (ABGD), 3) general mixed yule coalescent model (GMYC), and 4) poisson tree processes (bPTP). All molecular methods, traditional, geometric and lineal morphology were consistent in delimiting and recognizing the new species. Loxosceles tenochtitlan sp. nov. is closely related to L. misteca based on molecular data. Although both species are morphologically similar, the average p-distance from CO1 data was 13.8% and 4.2% for ITS2 data. The molecular species delimitation methods recovered well-supported monophyletic clusters for samples of L. tenochtitlan sp. nov. from Mexico City + Tlaxcala and for samples of L. misteca from Guerrero. Loxosceles tenochtitlan sp. nov. is considered a unique species for three reasons: (1) it can be distinguished by morphological characters (genitalic and somatic); (2) the four different molecular species delimitation methods were congruent to separate both species; and (3) there is variation in leg I length of males between both species, with the males of L. misteca having longer legs than males of L. tenochtitlan sp. nov., also morphometrically, the shape of tibiae of the palp between males of both species is different.

[Spider bite or infection caused by Panton Valentine leucocidin-producing Staphylococcusaureus?]

INTRODUCTION

Spiders, especially those of the genus Loxoceles such as L. rufescens, endemic in Mediterranean regions, are frequently reported as causes of venom poisoning in humans in the south of France. The most common signs consist of cutaneous necrosis presenting initially as inflammatory cellulitis and progressing towards the emergence of a necrotic centre.

PATIENTS AND METHODS

We report 4 cases, initially considered as spider bites due to their sudden occurrence and pain. Rigorous clinical examination coupled with collection of samples for laboratory analysis ultimately enabled the diagnosis to be corrected to one of suppurative skin infection caused by Staphylococcusaureus producing the cytotoxin Panton Valentine leucocidin.

DISCUSSION

These observations highlight the potential for confusion between spider bites and infections with PVL-producing S. aureus.

Brown recluse (L. rufescens) can bite in Northern Italy, too: first case report and review of the literature

The brown recluse, or fiddleback (violin) spider, is a poisonous spider of the Loxosceles genus that resides in warmer regions and old structures making the warm Mediterranean climate a natural habitat for the European species, L. rufescens Even in infested households, however, bites are rare, as they are nocturnal and unaggressive. In 2015, the first supposed death by L. rufescens occurred in Italy, but before and even after such bite, the literature on these spiders has been under-represented. This case report documents a confirmed bite by a violin spider on a medical student in Pavia, Italy. The presentation in this case was initially with general systemic, flu-like symptoms, then as cellulitis with lymphangitis that persisted for nearly 2 weeks until resolving without prolonged or complicated pathology. We present the first documented case of a L. rufescens bite in Northern Italy, to the best of our knowledge.

The kiss of (cell) death: can venom-induced immune response contribute to dermal necrosis following arthropod envenomations?

Introduction: Snakes, insects, arachnids and myriapods have been linked to necrosis following envenomation. However, the pathways involved in arthropod venom-induced necrosis remain a highly controversial topic among toxinologists, clinicians and the public. On the one hand, clinicians report on alleged envenomations based on symptoms and the victims' information. On the other hand, toxinologists and zoologists argue that symptoms are incompatible with the known venom activity of target species. This review draws from the literature on arthropod envenomations, snakebite, and inflammatory processes to suggest that envenomation by a range of organisms might trigger an intense inflammatory cascade that ultimately lead to necrosis. If confirmed, these processes would have important implications for the treatment of venom-induced necrosis. Objectives: To describe two inflammatory pathways of regulated necrosis, tumour necrosis factor (necroptosis) and Neutrophil Extracellular Traps (NETosis); to discuss existing knowledge about snake venom and arachnid-induced necrosis demonstrating the involvement of tumour necrosis factor and neutrophils in the development of tissue necrosis following envenomation and to contribute to the understanding of venom-induced necrosis by arthropods and provide clinicians with an insight into little known inflammatory processes which may occur post envenomation. Methods: ISI Web of Science databases were searched using the terms "spider bite necrosis", "arthropod envenomation necrosis", "venom necrosis", "venom immune response", "loxoscelism", "arachnidism", "necroptosis venom", "necroptosis dermatitis", "tumour necrosis factor TNF venom", "scorpionism", "scolopendrism", "centipede necrosis", "NETosis venom", "NETosis necrosis". Searches produced 1737 non-duplicate citations of which 74 were considered relevant to this manuscript. Non-peer-reviewed sources or absence of voucher material identifying the organism were excluded. What is necrosis? Necrosis is the breakdown of cell membrane integrity followed by inflowing extracellular fluid, organelle swelling and the release of proteolytic enzymes into the cytosol. Necrosis was historically considered an unregulated process; however, recent studies demonstrate that necrosis can also be a programmed event resulting from a controlled immune response (necroptosis). Tumour necrosis factor and the necroptosis pathway: Tumour necrosis factor is a pro-inflammatory cytokine involved in regulating immune response, inflammation and cell death/survival. The pro-inflammatory cytokine TNF-α participates in the development of necrosis after envenomation by vipers. Treatment with TNF-α-antibodies may significantly reduce the manifestation of necrosis. Neutrophil Extracellular Traps and the NETosis pathway: The process by which neutrophils discharge a mesh of DNA strands in the extracellular matrix to entangle ("trap") pathogens, preventing them from disseminating. Neutrophil Extracellular Traps have been recently described as important in venom-induced necrosis. Trapped venom accumulates at the bite site, resulting in significant localized necrosis. Arthropod venom driving necrosis: Insects, myriapods and arachnids can induce necrosis following envenomation. So far, the processes involved have only been investigated in two arachnids: Loxosceles spp. (recluse spiders) and Hemiscorpius lepturus (scorpion). Loxosceles venom contains phospholipases D which hydrolyse sphingomyelin, resulting in lysis of muscle fibers. Subsequently liberated ceramides act as intermediaries that regulate TNF-α and recruit neutrophils. Experiments show that immune-deficient mice injected with Loxosceles venom experience less venom-induced inflammatory response and survive longer than control mice. Necrosis following Hemiscorpius lepturus stings correlates with elevated concentrations of TNF-α. These observations suggest that necrosis may be indirectly triggered or worsened by pathways of regulated necrosis in addition to necrotic venom compounds. Conclusions: Envenomation often induce an intense inflammatory cascade, which under certain circumstances may produce necrotic lesions independently from direct venom activity. This could explain the inconsistent and circumstantial occurrence of necrosis following envenomation by a range of organisms. Future research should focus on identifying pathways to regulated necrosis following envenomation and determining more efficient ways to manage inflammation. We suggest that clinicians should consider the victim's immune response as an integral part of the envenomation syndrome.

The Mediterranean as a melting pot: Phylogeography of Loxosceles rufescens (Sicariidae) in the Mediterranean Basin

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.

A new species of Loxosceles Heineken & Lowe (Araneae, Sicariidae), with updated distribution records and biogeographical comments for the species from Mexico, including a new record of Loxoscelesrufescens (Dufour)

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.

Matching global and regional distribution models of the recluse spider Loxosceles rufescens: to what extent do these reflect niche conservatism?

The Mediterranean recluse spider, Loxosceles rufescens (Dufour, 1820) (Araneae: Sicariidae) is a cosmopolitan spider that has been introduced in many parts of the world. Its bite can be dangerous to humans. However, the potential distribution of this alien species, which is able to spread fairly quickly with human aid, is completely unknown. Using a combination of global and regional niche models, it is possible to analyse the spread of this species in relation to environmental conditions. This analysis found that the successful spreading of this species varies according to the region invaded. The majority of populations in Asia are stable and show niche conservatism, whereas in North America this spider is expected to be less successful in occupying niches that differ from those in its native region and that do not support its synanthropic way of living.

Probable cutaneous loxoscelism with mild systemic symptoms: A case report from Spain

We present a case from Valencia, Spain, of a 25-year-old woman who presented with a painful erythematous skin lesion, initially diagnosed as cellulitis. The lesion was unresponsive to antibiotic treatments and progressed into a hemorrhagic blister with necrotic ulcer formation. Posterior collection of a spider from the patient's home and expert identification of the spider as Loxosceles rufescens was achieved, establishing the diagnosis of probable cutaneous loxoscelism. Symptomatic treatment, general wound care and ultimately surgery, resulted in complete recovery with minor residual scarring. This case illustrates some of the difficulties encountered in the diagnosis and treatment of loxoscelism and adds to the increasing reports of loxoscelism in the Mediterranean Basin.

[What's new in clinical dermatology?]

In addition to continuous medical education, medical journals offer to dermatologists a huge variety of news that differ by their content, validity, originality and clinical relevance. I collected here various articles relative to clinical dermatology that have been published between September, 2016 and September, 2017. These papers have been chosen in the aim of reflecting such diversity. I just excluded, as far as possible, articles dealing with other issues that the reader will find further in this booklet (such as research, pediatric, instrumental, oncologic or therapeutic dermatology, or dermatology and internal medicine). Space restriction required to skip some commentaries while keeping the references to the selected papers, which the reader will be able to read carefully in its original form.

Dangerous arachnids-Fake news or reality?

The public perception of spiders and scorpions is skewed towards the potential harm they can inflict in humans, despite recent scientific evidence that arachnid venom components might be useful as bioinsecticides or even human therapeutics. Nevertheless, arachnids are becoming more popular as pets in Europe, America and Asia, raising the question for regulatory agencies in these regions as to whether they need to take measurements to protect their citizens. In order to decide upon the necessary regulatory steps, they first need to determine which arachnids are actually dangerous to humans. This review therefore provides an overview of the current literature on verified bites and stings from spiders and scorpions with the aim of assessing their potential danger for human health. As a guideline, we also provide a list of those arachnid genera that we consider as potentially dangerous, which includes 10 spider and 11 scorpion genera. The arachnid genera classified as dangerous comprise less than a quarter of all extant scorpion species and only 0.5% of all spiders species, with the actual number most likely being much lower than that, as not all species in those genera might turn out to pose an actual threat for humans. In conclusion, we found that only a small percentage of scorpions and a minute percentage of all spiders can be considered as potentially dangerous to humans. While in some countries of origin the high incidence of envenomations by dangerous arachnids can result in a serious problem to the health system, we assessed the risk that the same species pose when kept as pets under controlled maintenance conditions as significantly lower.