Antivenom treatment in arachnidism

Development and Efficacy of the Antivenom Specific to Severe Envenomations in Morocco and North Africa: Advancements in Scorpion Envenomation Management

Scorpion envenomation poses a global public health issue, with an estimated 1,500,000 cases worldwide annually resulting in 2600 deaths. North Africa, particularly Morocco, experiences severe envenomations, mainly attributed to Androctonus mauretanicus and Buthus occitanus in Morocco, and Buthus occitanus and Androctonus australis hector in Algeria and Tunisia, with case numbers often underestimated. Current treatment relies mainly on symptomatic approaches, except in Morocco, where management is limited to symptomatic treatment due to controversies regarding specific treatment. In Morocco, between 30,000 and 50,000 scorpion envenomation cases are reported annually, leading to hundreds of deaths, mainly among children. Controversies among clinicians persist regarding the appropriate course of action, often limiting treatments to symptomatic measures. The absence of a specific antivenom for the venoms of the most lethal scorpions further exacerbates the situation. This study aims to address this gap by developing a monovalent antivenom against the endemic and most dangerous scorpion, Androctonus mauretanicus. The antivenom was produced by immunizing albino rabbits with a mixture of Androctonus mauretanicus venom collected from high-risk areas in Morocco. Immunizations were performed by subcutaneous injections at multiple sites near the lymphatic system, following an immunization schedule. Production control of neutralizing antibody titers was conducted through immunodiffusion. Once a sufficient antibody titer was achieved, blood collection was performed, and the recovered plasma underwent affinity chromatography. The efficacy of purified IgG was evaluated by determining the ED50 in mice, complemented by histological and immunohistochemical studies on its ability to neutralize venom-induced tissue alterations and the neutralization of toxins bound to receptors in the studied organs. The monovalent antivenom demonstrated specificity against Androctonus mauretanicus venom and effective cross-protection against the venom of the scorpions Buthus occitanus and Androctonus australis hector, highly implicated in lethal envenomations in the Maghreb. This study shows that the developed monovalent antivenom exhibits notable efficacy against local scorpions and a surprising ability to neutralize the most lethal envenomations in North Africa. These results pave the way for a new, more specific, and promising therapeutic approach to countering severe scorpion envenomations, especially in Morocco, where specific treatment is lacking.

Clinical Evolution After Administering Antivenom in Patients With Loxoscelism

Spiders are the most numerous arthropods of the arachnid class. More than 45 thousand species of spiders have been identified, and only a few are dangerous to humans. Among them, the "violin spider" or "brown spider" of the genus Loxosceles (family Sicariidae) has a worldwide distribution, and its bite can cause loxoscelism. Initial treatment of a Loxosceles spider bite includes application of local cold, rest, elevation of the extremity if possible, and systemic pharmacotherapy with antihistamines, corticosteroids, antibiotics, polymorphonuclear inhibitors, and analgesics or nonsteroidal anti-inflammatory drugs. During cutaneous or systemic loxoscelism, administration of Loxosceles antivenom (immunoglobulin (Ig)G F(ab')2 fragments) may be indicated to prevent progression to severe systemic phases. In this manuscript, we present three cases of patients with loxoscelism treated with the fabotherapeutic Reclusmyn®, developed and manufactured in Mexico. Two patients had a satisfactory outcome without severe skin or systemic damage. Only one patient with loxoscelism, despite early initiation of antivenom, had extensive skin lesions that healed satisfactorily, leaving only a non-disabling scar. Due to the global presence of this clinical problem, further studies are needed to establish local and general guidelines for the treatment and prevention of loxoscelism. This will allow health professionals to provide more efficient and higher quality medical care and feel supported in their decisions.

Acute-on-Chronic Liver Failure Triggered by Cutaneous Loxoscelism

Acute-on-chronic liver failure is a syndrome associated with a high short-term mortality rate. Severe systemic inflammation and single- and multiple-organ failure are a hallmark of this syndrome, with pro-inflammatory precipitating events occurring in the liver or extrahepatic regions. We report a case of a 69-year-old man with a previous diagnosis of alcohol-induced liver cirrhosis who presented with a poorly defined, erythematous-purplish, and edematous plaque with multiple hemorrhagic blisters over the left leg, one day after receiving a spider bite. During the following hours, the skin lesion progressed, and the patient developed hepatic encephalopathy, respiratory failure, and arterial hypotension, requiring the administration of vasopressors; blood analysis revealed hypercreatininemia, an elevated international normalized ratio (INR) value, and hyperbilirubinemia. The patient was diagnosed with acute-on-chronic liver failure caused by cutaneous loxoscelism. There was no hemolytic anemia, rhabdomyolysis, or disseminated intravascular coagulation in the patient, thus excluding the possibility of visceral loxoscelism.

Seasonal variation, treatment outcome, and its associated factors among the snakebite patients in Somali region, Ethiopia

Background

Snakebite is a major cause of mortality and morbidity in many areas, particularly in the rural tropics, and is a major public health problem around the world. It also imposes significant economic burdens on snakebite victims due to treatment-related expenses and lost productivity.

Objective

The purpose of this study was to assess seasonal variation, treatment outcomes, and its associated factors among snakebite in Denan health center in the Somali region, Ethiopia.

Method

A facility-based cross-sectional study was conducted from 10 to 30 September 2020 in Denan health center, Somali region, Ethiopia. All snakebite cases in Denan health center from 1 September 2015 to 31 August 2020 were included. Data were collected using a pre-tested structured checklist from the patient cards. Data were entered into EpiData version 3.1 and analyzed using SPSS version 22 (IBM SPSS Statistics, 2013). The prevalence was reported by proportion with 95% confidence interval (CI) and summary measures. Predictors were assessed using a multivariable logistic regression analysis model and reported using an adjusted odds ratio with 95% CI. Statistical significance was declared at p-value < 0. 05.

Result

The overall prevalence of poor outcome of venomous snakebites was 31.4% (95% CI 26.3% 35.4%). Study participants with an age of less than 10 years old (AOR = 2.01; 95% CI 1.39, 4.05), age between 10 and 30 years old (AOR = 2.06; 95% CI 1.39, 9.30), arrival times greater than or equal to 6 hours (AOR = 2.37; 95% CI 1.39, 4.05), and timing of snakebite (AOR = 0.49; 95% CI 0.31-0.87) were factors found to be significantly associated with poor treatment outcome.

Conclusion

According to this study, about one in every three snakebite patients have a poor outcome. Patients with poor outcomes were those who did not improve as a result of treatment or died as a result of it. Designing appropriate engagement of public health education about snakebite prevention techniques, particularly during entry and exit of rainy seasons and establishment of appropriate case management protocol is strongly recommended, as well as increasing the accessibility or availability of antivenoms will undoubtedly have a significant impact on the reduction of mortality and disability related to that of the snakebites.

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.

Coexistence of Rhabdomyolysis, Myocarditis and Arrhythmia after Spider Bite: A Case Report

BACKGROUND

Rhabdomyolysis after spider bite has been reported in a small number of patients, and myocarditis in even fewer. However, arrhythmia associated with latrodectism in children has not been described in the literature to date.

CASE SUMMARY

A girl presented approximately 4.5 h after being bitten on the left ankle by a black spider. Two unifocal premature ventricular contractions (PVCs) were observed on the electrocardiogram. In laboratory tests, creatine kinase was elevated. On day 2, levels of troponin, pro-brain and natriuretic peptide were elevated. Electrocardiogram revealed inverted and biphasic T waves. Echocardiography revealed mild left ventricular dilation, mitral and aortic valve regurgitation. Holter electrocardiogram showed PVCs. Her laboratory and echocardiography findings completely normalized after discharge, and no arrhythmia was observed on the Holter electrocardiogram during outpatient follow-up.

CONCLUSION

Although spider bites are uncommon, they can cause serious systemic effects. These patients should be evaluated for arrhythmia, rhabdomyolysis and myocarditis.

Terrestrial venomous animals, the envenomings they cause, and treatment perspectives in the Middle East and North Africa

The Middle East and Northern Africa, collectively known as the MENA region, are inhabited by a plethora of venomous animals that cause up to 420,000 bites and stings each year. To understand the resultant health burden and the key variables affecting it, this review describes the epidemiology of snake, scorpion, and spider envenomings primarily based on heterogenous hospital data in the MENA region and the pathologies associated with their venoms. In addition, we discuss the venom composition and the key medically relevant toxins of these venomous animals, and, finally, the antivenoms that are currently in use to counteract them. Unlike Asia and sub-Saharan Africa, scorpion stings are significantly more common (approximately 350,000 cases/year) than snakebites (approximately 70,000 cases/year) and present the most significant contributor to the overall health burden of envenomings, with spider bites being negligible. However, this review also indicates that there is a substantial lack of high-quality envenoming data available for the MENA region, rendering many of these estimates speculative. Our understanding of the venoms and the toxins they contain is also incomplete, but already presents clear trends. For instance, the majority of snake venoms contain snake venom metalloproteinases, while sodium channel-binding toxins and potassium channel-binding toxins are the scorpion toxins that cause most health-related challenges. There also currently exist a plethora of antivenoms, yet only few are clinically validated, and their high cost and limited availability present a substantial health challenge. Yet, some of the insights presented in this review might help direct future research and policy efforts toward the appropriate prioritization of efforts and aid the development of future therapeutic solutions, such as next-generation antivenoms.

Widow spiders in the New World: a review on Latrodectus Walckenaer, 1805 (Theridiidae) and latrodectism in the Americas

Humankind has always been fascinated by venomous animals, as their toxic substances have transformed them into symbols of power and mystery. Over the centuries, researchers have been trying to understand animal venoms, unveiling intricate mixtures of molecules and their biological effects. Among venomous animals, Latrodectus Walckenaer, 1805 (widow spiders) have become feared in many cultures worldwide due to their extremely neurotoxic venom. The Latrodectus genus encompasses 32 species broadly spread around the globe, 14 of which occur in the Americas. Despite the high number of species found in the New World, the knowledge on these spiders is still scarce. This review covers the general knowledge on Latrodectus spp. from the Americas. We address widow spiders' taxonomy; geographical distribution and epidemiology; symptoms and treatments of envenomation (latrodectism); venom collection, experimental studies, proteome and transcriptome; and biotechnological studies on these Latrodectus spp. Moreover, we discuss the main challenges and limitations faced by researchers when trying to comprehend this neglected group of medically important spiders. We expect this review to help overcome the lack of information regarding widow spiders in the New World.

Scorpion Stings in Saudi Arabia: An Overview

Background and aim of the work:

Scorpion sting envenomation is an important cause of morbidity and mortality among incidents caused by envenomations, especially in children and elderly, worldwide. In Saudi Arabia, it is an important issue as the climate and the desert terrain are ideal for scorpions’ habitat. The aim of this review is to emphasize on the importance of scorpion stings in Saudi Arabia and provide updates regarding scorpion types and epidemiological aspects of scorpion stings in Saudi Arabia.

Methods:

Aliterature review of articles on scorpions and scorpion stings in Saudi Arabia.

Results:

In Saudi Arabia, at least 28 species of scorpions are identified. An estimated 14,500 scorpion stings are annually documented in various regions of Saudi Arabia. Most of the cases of scorpion envenomation recover completely with treatment in Saudi Arabia. People who live in the desert terrain, such as nomads or shepherds, are the population at highest risk for scorpion stings. The highest incidence of scorpion stings is reported during the summer season.

Conclusion:

Scorpions are found to inhabit all the regions of the country. The incidence of scorpion stings in Saudi Arabia seems to be significant. However, the mortality rate is low in Saudi Arabia. There are insufficient studies regarding this topic, and as such, it is clear that there is a lack of information regarding autopsy findings of scorpion sting deaths in Saudi Arabia. (www.actabiomedica.it)

Brown Spiders' Phospholipases-D with Potential Therapeutic Applications: Functional Assessment of Mutant Isoforms

Phospholipases-D (PLDs) found in Loxosceles spiders' venoms are responsible for the dermonecrosis triggered by envenomation. PLDs can also induce other local and systemic effects, such as massive inflammatory response, edema, and hemolysis. Recombinant PLDs reproduce all of the deleterious effects induced by Loxosceles whole venoms. Herein, wild type and mutant PLDs of two species involved in accidents-L. gaucho and L. laeta-were recombinantly expressed and characterized. The mutations are related to amino acid residues relevant for catalysis (H12-H47), magnesium ion coordination (E32-D34) and binding to phospholipid substrates (Y228 and Y228-Y229-W230). Circular dichroism and structural data demonstrated that the mutant isoforms did not undergo significant structural changes. Immunoassays showed that mutant PLDs exhibit conserved epitopes and kept their antigenic properties despite the mutations. Both in vitro (sphingomyelinase activity and hemolysis) and in vivo (capillary permeability, dermonecrotic activity, and histopathological analysis) assays showed that the PLDs with mutations H12-H47, E32-D34, and Y228-Y229-W230 displayed only residual activities. Results indicate that these mutant toxins are suitable for use as antigens to obtain neutralizing antisera with enhanced properties since they will be based on the most deleterious toxins in the venom and without causing severe harmful effects to the animals in which these sera are produced.

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.

Latrodectism in Italy: First report of successful treatment of L. tredecimguttatus envenomation using L. mactans antivenom from North America

INTRODUCTION

Latrodectism is a rare, but potentially severe, clinical syndrome caused by spider of the genus Latrodectus. L. tredecimguttatus is widespread in Italy and its bite cause the injection of α-latrotoxin that cause depletion of acetylcholine at motor nerve endings and release of catecholamines at adrenergic nerve endings. We describe the first clinical case of L. tredecimguttatus poisoning successfully treated with L. mactans antivenom from North America.

CASE REPORT

A healthy 60-year-old patient was admitted to the emergency department after unknown insect sting or arachnid/snake bite. In the early morning, the patient was working in the countryside when he felt a sting-like pain in the medial area of the right lower leg, associated with an intense burning sensation. An hour later he developed agitation, hoarseness, sweating, abdominal distress and intense pain in his right leg. In the emergency room vital signs showed a hypertensive crisis, tachycardia and peripheral oxygen desaturation. ECG was normal and ABE showed mixed acid-base disorder. Blood tests showed leukocytosis with neutrophilia, high levels of myoglobin, with normal coagulation and normal plasmatic cholinesterase. Neck, thorax and abdomen CT scan, with and without contrast medium, was negative. Four hours after admission hypertension worsened with board like rigid abdomen and onset of fasciculations, tremors, miosis and intense regional sweating. The definitive diagnosis of poisoning by L tredecimguttatus was based on the clinical picture. Within short time the antidote was provided by the Poison Centre and administered. A marked improvement of the symptomatology was noted after 30 minutes, and 1 hour later all symptoms were under control. The patient was discharged after 2 days.

CONCLUSIONS

The clinical presentation of a patient suffering from latrodectism places the clinician in front of a challenging differential diagnosis. Following the suspicion, the first-line doctor is invited to discuss the case with a toxicologist, in order to confirm or exclude the diagnosis and implement all therapeutic measures. In our clinical case, the absence of organic lesions, laboratory tests not suggestive for other causes, and the presence of typical clinical feature suggested the diagnosis of L tredecimguttatus poisoning. This hypothesis was then supported by the close temporal relation between antivenom administration and symptoms improvement. With this case, we report the first use of L mactans antivenom from North America to treat L.tredecimguttatus poisoning and we confirm its effectiveness in counteracting latrodectism caused by this spider.

Low-dose ketamine provides poor analgesia for pain in redback spider envenoming

Redback spider envenoming causes severe pain lasting several days. A recent clinical trial found that antivenom is not effective. We investigated ketamine for pain in redback spider envenoming. Ten adult patients with severe pain from redback spider envenoming were administered 15 mg intravenous ketamine after standard analgesia, then up to 4 oral doses of ketamine 25- 50 mg. Three patients had a clinically significant improvement in pain compared to baseline after intravenous ketamine. Five patients had a minimal decrease in pain and 2 had no improvement. Eight patients received oral ketamine: 4 doses in 5 and 2 doses in 3. At 24 h, 3/6 patients assessed had clinically significant improvement in pain and 4/5 patients assessed at 48 h, had clinically significant improvement in pain. Six patients reported side effects, including dissociation (4) and hallucinations (2). Five patients required rescue opioids and 2 were readmitted to hospital. We found that ketamine provided no additional pain relief in redback spider envenoming, compared to standard analgesia, and resulted in unacceptable adverse effects.

Treatments for Latrodectism-A Systematic Review on Their Clinical Effectiveness

Latrodectism or envenomation by widow-spiders is common and clinically significant worldwide. Alpha-latrotoxin is the mammalian-specific toxin in the venom that results in toxic effects observed in humans. Symptoms may be incapacitating and include severe pain that can persist for days. The management of mild to moderate latrodectism is primarily supportive while severe cases have variously been treated with intravenous calcium, muscle relaxants, widow-spider antivenom and analgesic opioids. The object of this systematic review is to examine the literature on the clinical effectiveness of past and current treatments for latrodectism. MEDLINE, EMBASE and Google Scholar were searched from 1946 to December 2016 to identify clinical studies on the treatment of latrodectism. Studies older than 40 years and not in English were not reviewed. There were only two full-publications and one abstract of placebo-controlled randomised trials on antivenom use for latrodectism. Another two randomised comparative trials compared the route of administration of antivenom for latrodectism. There were fourteen case series (including two abstracts), fourteen case reports and one letter investigating drug treatments for latrodectism with the majority of these also including antivenom for severe latrodectism. Antivenom with opioid analgesia is often the major treatment reported for latrodectism however; recent high quality evidence has cast doubt on the clinical effectiveness of this combination and suggests that other treatments need to be investigated.

Lymphangitis From Scolopendra heros Envenomation: The Texas Redheaded Centipede

Envenomation by Scolopendra heros, the Texas redheaded centipede, can present variably. Although transient pain and erythema are often treated conservatively, complications may include cellulitis, necrosis, myocardial infarction, and rhabdomyolysis. We present a case of an elderly man who came to the emergency department with lymphangitis and dermatitis secondary to a centipede sting that awoke him from sleep. It is important to recognize the potential of centipede envenomation to have severe local and systemic manifestations.

Lethality and histopathological alterations caused by Phoneutria nigriventer spider venom from Argentina: Neutralization of lethality by experimental and therapeutic antivenoms

Although the spiders of the genus Phoneutria cause envenomation and their presence has been described in several provinces of the north of Argentina, they are not as common as other spiders of sanitary importance. In the present work, we studied the toxicity of samples of venom of Phoneutria spiders from the provinces of Misiones (where severe envenomation and deaths by Phoneutria have been recorded) and Jujuy (where no deaths have been recorded and severe envenomations are not frequent). To this end, we assessed the lethal potency in mice and guinea pigs and the histopathological alterations caused by both venoms, as well as the neutralization by the commonly used therapeutic antivenom produced by the Butantan Institute in Brazil and by an experimental antivenom developed with venom of P. nigriventer from Misiones. There were no differences in the lethality of the venoms of spiders from both regions. Post mortem examination showed that the heart and lungs were the most affected organs, while important pulmonary edema was seen macroscopically. Histological analysis showed edema, atelectasis, emphysema and cardiac lesion in both experimental models. The antivenoms assayed showed good neutralization of the venoms in the two experimental models. Despite the different geographic origins, the venoms showed similar toxicity and both the experimental antivenom and therapeutic antivenmos were able to neutralize the venoms of Argentinean P. nigriventer.

Low Health System Performance, Indigenous Status and Antivenom Underdosage Correlate with Spider Envenoming Severity in the Remote Brazilian Amazon

Background

A better knowledge of the burden and risk factors associated with severity due to spider bites would lead to improved management with a reduction of sequelae usually seen for this neglected health problem, and would ensure proper use of antivenoms in remote localities in the Brazilian Amazon. The aim of this study was to analyze the profile of spider bites reported in the state of Amazonas in the Western Brazilian Amazon, and to investigate potential risk factors associated with severity of envenomation.

Methodology/Principal Findings

We used a case-control study in order to identify factors associated with spider bite severity in the Western Brazilian Amazon from 2007 to 2014. Patients evolving to any severity criteria were considered cases and those with non-severe bites were included in the control group. All variables were retrieved from the official Brazilian reporting systems. Socioeconomical and environmental components were also included in a multivariable analysis in order to identify ecological determinants of incidence and severity. A total of 1,181 spider bites were recorded, resulting in an incidence of 4 cases per 100,000 person/year. Most of the spider bites occurred in males (65.8%). Bites mostly occurred in rural areas (59.5%). The most affected age group was between 16 and 45 years old (50.9%). A proportion of 39.7% of the bites were related to work activities. Antivenom was prescribed to 39% of the patients. Envenomings recorded from urban areas [Odds ratio (OR) = 0.40 (95%CI = 0.30–0.71; p<0.001)] and living in a municipality with a mean health system performance index (MHSPI >median [OR = 0.64 (95%CI = 0.39–0.75; p<0.001)] were independently associated with decreased risk of severity. Work related accidents [OR = 2.09 (95%CI = 1.49–2.94; p<0.001)], Indigenous status [OR = 2.15 (95%CI = 1.19–3.86; p = 0.011)] and living in a municipality located >300 km away from the state capital Manaus [OR = 1.90 (95%CI = 1.28–2.40; p<0.001)] were independently associated with a risk of severity. Living in a municipality located >300 km away from the state capital Manaus [OR = 1.53 (95%CI = 1.15–2.02; p = 0.003)] and living in a municipality with a MHSPI <median [OR = 1.91 (95%CI = 1.28–2.47; p = 0.002)] increased the odds of antivenom underdosage.

Conclusions

Spider bites is prevalent across the study region with a higher incidence in the rainy season in rural areas. Spider bites can be painful and lead to local manifestations but rarely result in life-threatening envenoming. Major local complications were dermonecrosis and secondary infection in cases diagnosed as Loxosceles bites. Based on the correlations shown here, envenomings occurring in remote rural areas, Indigenous status and living in a municipality located >300 km away from the state capital Manaus could be contributing factors to higher severity of spider envenomings in this area, as well as to antivenom underdosage.

Antibacterial activity of the venom of Heterometrus xanthopus

Heterometrus xanthopus (Scorpion) is one of the most venomous and ancient arthropods. Its venom contains anti-microbial peptides like hadrurin, scorpine, Pandinin 1, and Pandinin 2 that are able to effectively kill multidrug-resistant pathogens. The present study was conducted to evaluate the anti-bacterial activity of H. xanthopus venom. Six Gram-positive and Gram-negative bacterial strains were tested against 1/100, 1/10, and 1/1 fractions of distilled water diluted and crude venom. 1/100 and 1/10 dilutions were not successful in any of the six bacterial strains studied while the 1/1 dilution was effective on Bacillus subtilis ATCC 6633, Salmonella typhimurium ATCC 14028, and Pseudomonas aeruginosa ATCC 27853 with highest zone of inhibition were obtained on B. subtilis. Crude venom was effective against Enterococcus faecalis ATCC 14506, B. subtilis, S. typhimurium, and P. aeruginosa. The most effective results were observed on B. subtilis.

Neurotoxic emergencies

This article is intended for clinicians treating neurotoxic emergencies. Presented are causative agents of neurotoxic emergencies, many of which are easily mistaken for acute psychiatric disorders. Understanding the wide variety of agents responsible for neurotoxic emergencies and the neurotransmitter interactions involved will help the psychiatrist identify and treat this challenging population.

A clinical and epidemiological study on spider bites in Turkey

OBJECTIVE

To classify and characterize spider bites among inquiries to the National Poison Information Center (NPIC) between 1995 and 2004, in terms of the epidemiology and clinical symptomatology.

METHODS

Clinical and epidemiological data were obtained from the NPIC's patient records. The following information was recorded for each spider bite: demographics, circumstances of the bite, and local and systemic effects.

RESULTS

A total of 82 cases were reported. The accidents were mostly seen during August. The gender distribution was 59.76% male, 37.20% female, and 2.44% unknown and the 20-29 age group presented more spider bites. Most of the cases were in the Central Anatolia, Marmara, Mediterranean, and Black Sea regions. Local symptoms were observed in 60.87% of the cases, including local pain, edema, redness, itching, debris, burning, and numbness. Systemic symptoms were observed such as nausea, vomiting, abdominal pain, lethargy, anxiety, weakness, somnolence, dyspnea, hypertension, hypotension, and hyperthermia.

CONCLUSIONS

In conclusion, these findings emphasize the presence of medically important spider species in Turkey. All patients and especially pediatric patients should be admitted to the hospital. Identification of spider species may be considered a useful clinical and epidemiological tool in determining the incidence and risk of spider bites.

Spider bite

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

A US Perspective of Symptomatic Latrodectus spp. Envenomation and Treatment: A National Poison Data System Review

Background:

Black widow spider (Latrodectus spp.) envenomation remains the most clinically significant spider envenomation in the US. The syndrome is characterized by painful muscle rigidity and autonomic disturbances. Treatment has ranged from symptomatic care to administration of specific antivenom. Declining antivenom availability and, possibly, the fear of hypersensitivity allergic reactions, has limited antivenom use in the US.

Objective:

To describe Latrodectus spp. exposures and the subsequent treatment reported to US poison centers; the secondary objective was to Identify factors associated with shorter duration of symptoms (<24 hours).

Methods:

All Latrodectus spp. exposures reported to the National Poison Data System (NPDS) between January 1, 2000, and December 31, 2008, were reviewed. Cases with at least minor clinical effects due to Latrodectus spp. exposure were extracted. Descriptive statistics were generated. The probability that symptom duration was less than 24 hours was modeled, using logistic regression.

Results:

From 2000 through 2006, a total of 23,409 Latrodectus spp. exposures were reported in 47 states; 9872 cases had at least minor clinical effects and were included in the subsequent analysis. Exposures peaked in September and fell to a nadir in January and February. Fifty-eight percent of the cases involved males, and the mean (SD) age was 31.5 (17.4) years. Sixty-five percent of the patients had minor clinical effects, 33.5% had moderate effects, 1.4% had major effects, and there were no deaths. Antivenom use was associated with symptom duration of less than 24 hours in moderate and major outcome groups. There was no evidence of shorter symptom duration in patients who received benzodiazepines or calcium. Adverse drug reactions were more common in patients receiving benzodiazepines and antivenom.

Conclusions:

In the US, most symptomatic Latrodectus spp. exposures reported to the NPDS are minor. Few patients receive antivenom, although antivenom is associated with shorter symptom duration among moderate and major outcomes.

Exploiting cross-reactivity to neutralize two different scorpion venoms with one single chain antibody fragment

We report the optimization of a family of human single chain antibody fragments (scFv) for neutralizing two scorpion venoms. The parental scFv 3F recognizes the main toxins of Centruroides noxius Hoffmann (Cn2) and Centruroides suffusus suffusus (Css2), albeit with low affinity. This scFv was subjected to independent processes of directed evolution to improve its recognition toward Cn2 (Riaño-Umbarila, L., Juárez-González, V. R., Olamendi-Portugal, T., Ortíz-León, M., Possani, L. D., and Becerril, B. (2005) FEBS J. 272, 2591-2601) and Css2 (this work). Each evolved variant showed strong cross-reactivity against several toxins, and was capable of neutralizing Cn2 and Css2. Furthermore, each variant neutralized the whole venoms of the above species. As far as we know, this is the first report of antibodies with such characteristics. Maturation processes revealed key residue changes to attain expression, stability, and affinity improvements as compared with the parental scFv. Combination of these changes resulted in the scFv LR, which is capable of rescuing mice from severe envenomation by 3 LD(50) of freshly prepared whole venom of C. noxius (7.5 μg/20 g of mouse) and C. suffusus (26.25 μg/20 g of mouse), with surviving rates between 90 and 100%. Our research is leading to the formulation of an antivenom consisting of a discrete number of human scFvs endowed with strong cross-reactivity and low immunogenicity.

Molecular diversity of spider venom

Spider venom, a factor that has played a decisive role in the evolution of one of the most successful groups of living organisms, is reviewed. Unique molecular diversity of venom components including substances of variable structure (from simple low molecular weight compounds to large multidomain proteins) with different functions is considered. Special attention is given to the structure, properties, and biosynthesis of toxins of polypeptide nature.

Latrodectism in New Caledonia: first report of presumed redback spider (Latrodectus hasselti) envenomation

We describe a recent case of presumed redback spider (Latrodectus hasselti) envenomation observed near Noumea in New Caledonia. This is the first local reported case in this archipelago, where L. hasselti is currently considered a native species. We highlight the challenge of providing appropriate analgesia in this situation and believe that the use of specific redback spider antivenom should be considered in New Caledonia.

Spider bite (latrodectism) in Mashhad, Iran

Background: Spider (Latrodectus tredecimguttatus) bites are relatively common in North East Iran. They induce morbidity and rarely mortality. We aimed to investigate clinical, electrocardiographic and para-clinical changes in patients with this bite. Methods: All consecutive patients admitted with suspected spider bites between September 2005 and September 2006 were studied prospectively. Results: Spider bites accounted for 56 cases (0.5% of all poisoning, 21% of all admitted envenomated). The patients’ mean (SD) age was 32 (16) years. The most common findings were pain (90%) mainly in their back (45%), stomach (35%), lower limbs (33%), upper limbs (19%) and chest (14%). Other clinical findings included were sweating (55%), chills (29%), dyspnea (25%), flushing (14%), spasm (12%), headache (12%), nausea (12%) and vertigo (12%). On electrocardiograph (ECG); ST segments were depressed in 25% of cases in at least two of the pre-cordial leads. Laboratory findings were in normal ranges. All the patients recovered following supportive and symptomatic treatment (no anti-toxin available in Iran), with a mean hospitalization period of 1.9 (1.3) days. Conclusions: Spider (L. Tredecimguttatus) bite is relatively common in Mashhad, which induces latrodectism with relatively different findings and cardiac toxicity. ECG monitoring should be considered, particularly when specific anti-toxin is not available.

Antivenom efficacy or effectiveness: the Australian experience

Despite widespread use of antivenoms, many questions remain about their effectiveness in the clinical setting. The almost universal acceptance of their value is based mainly on in vitro studies, animal studies and human observational studies. Numerous examples exist where they demonstrate clear benefit, such as consumption coagulopathy in viper envenoming, prevention of neurotoxicity in Australasian elapid bites, systemic effects in scorpion and funnel-web spider envenoming. There are also concerns about the quality and efficacy of some antivenoms. However, it is important not to confuse the efficacy of antivenom, defined as its ability to bind and neutralise venom-mediated effects under ideal conditions, and the effectiveness of antivenom, defined as its ability to reverse or prevent envenoming in human cases. There are numerous potential reasons for antivenom failure in human envenoming, of which antivenom inefficacy is only one. Other important reasons include venom-mediated effects being irreversible, antivenom being unable to reach the site of toxin-mediated injury, or the rapidity of onset of venom-mediated effects. A number of recent studies in Australia bring into question the effectiveness of some antivenoms, including snake antivenom for coagulopathy, redback spider and box jellyfish antivenoms. Despite brown snake antivenom being able to neutralise venom induced clotting in vitro, use of the antivenom in human envenoming does not appear to change the time course of coagulopathy. However, it is important that apparent antivenom ineffectiveness in specific cases is correctly interpreted and does not lead to a universal belief that antivenom is ineffective. It should rather encourage further studies to investigate the underlying pathophysiology of envenoming, the pharmacokinetics of venoms and antivenoms, and ultimately the effectiveness of antivenom based on snake type, clinical effects and timing of administration.

A randomised controlled trial of intramuscular vs. intravenous antivenom for latrodectism--the RAVE study

BACKGROUND

Widow spider-bite causes latrodectism and is associated with significant morbidity worldwide. Antivenom is given by both the intravenous (IV) and intramuscular (IM) routes and it is unclear which is more effective.

AIM

To compare the effectiveness of IV vs. IM redback spider antivenom.

DESIGN

Randomized controlled trial.

METHODS

Patients with latrodectism were given either IV or IM antivenom according to a randomized double-dummy, double-blind protocol. The first antivenom treatment was followed by another identical treatment after two hours if required. The primary outcome was a clinically significant reduction in pain two hours after the last treatment. A fully Bayesian analysis was used to estimate the probability of the desired treatment effect, predetermined as an absolute difference of 20%.

RESULTS

We randomly allocated 126 patients to receive antivenom IV (64) and IM (62). After antivenom treatment pain improved in 40/64(62%) in the IV group vs. 33/62(53%) in the IM group (+9%; 95% Credible Interval [CrI]: -8% to +26%). The probability of a difference greater than zero (IV superior) was 85% but the probability of a difference >20% was only 10%. In 55 patients with systemic effects, these improved in 58% after IV antivenom vs. 65% after IM antivenom (-8%; 95% CrI: -32% to +17%). Twenty-four hours after antivenom pain had improved in 84% in the IV group vs. 71% in the IM group (+13%; 95% CrI: -2% to +27%). A meta-analysis including data from a previous trial found no difference in the primary outcome between IV and IM administration.

DISCUSSION

The difference between IV and IM routes of administration of widow spider antivenom is, at best, small and does not justify routinely choosing one route over the other. Furthermore, antivenom may provide no benefit over placebo.

Medical aspects of spider bites

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

Toxicity of two North American Loxosceles (brown recluse spiders) venoms and their neutralization by antivenoms

The toxic, biochemical, and immunological characteristics of L. boneti and L. reclusa venoms and its neutralization by anti-L. boneti and anti-L. reclusa antivenoms were studied. The electrophoretic profile showed very similar patterns and the toxic activities were very close. Immunological studies showed cross-reactivity among L. boneti and L. reclusa venoms, with L. boneti and L. reclusa experimental antivenoms, and anti-L. gaucho and anti-L. laeta antivenoms. The venom of L. laeta showed low immunological reactivity with the North American Loxosceles antivenoms. Experimental anti-North American Loxosceles antivenoms protected mice of the systemic toxicity and were able to prevent necrosis in rabbit skin after the injection of the venom. Both antivenoms displayed cross neutralization. The results showed that both Loxosceles venoms have very close toxic, biochemical, and immunological characteristics, and that either monospecific antivenoms or an antivenom raised with L. boneti and L. reclusa venoms as immunogens could be useful for treating bites by North American Loxosceles spiders.