Snakebite Envenoming a Challenging Diagnosis for the Forensic Pathologist: A Systematic Review

Therapeutic potency of kaempferol against Naja haje venom induced neurotoxicity, inflammation, biological activities, and antioxidant system damage: a pre-clinical antivenom evaluation

Naja haje envenoming manifests organ system disorders leading to severe fatalities due to the venom's toxins. The neutralizing capacity of kaempferol has been reported against some medically significant snake venoms with exception of N. haje venom (NhV). This current study assessed the neutralizing profile of kaempferol against toxicities induced by NhV using in vitro and in vivo methods. In in vitro, NhV induced wide spectrum of toxic biological activities with substantial increase in hemorrhagic, anticoagulating, and hemolytic effects. Likewise in the in vivo study, the venom caused hematological disorders by inducing acute anemia, thrombocytopenia, and leucopenia in envenomed rats. Also, the venom caused detrimental effect on the antioxidant defense system of the brain through significant (P < 0.05) elevation of malondialdehyde (MDA), nitrite (NIT), and suppression of reduce glutathione (GSH) antioxidant, superoxide dismutase (SOD), catalase (CAT), and glutathione transferase (GST) enzymes. Additionally, the levels of neurotoxicity biomarkers, monoamine oxidase (MAO) and acetylcholinesterase (AChE), and pro-inflammatory cytokines, tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6), were significantly (P < 0.0.5) enhanced by NhV in the brain of envenomed rats. Severe pathohistological effects were observed in brain tissues of the envenomed rats. However, kaempferol substantially (P < 0.05) inhibited the NhV-induced biological activities, normalized the hematological disorders, enhanced antioxidants system functions, and significantly (P < 0.05) suppressed the levels of neurotoxicity biomarkers and pro-inflammatory cytokines. Severe structural alterations observed in the brain tissues were ameliorated after kaempferol treatment. Further exploration of kaempferol could lead to the development of an alternative therapy for treatment of N. haje envenoming.

Dermatopathological findings of Bothrops atrox snakebites: A case series in the Brazilian Amazon

BACKGROUND

Bothrops venom consists primarily of metalloproteinase and phospholipase A2 toxins, which are responsible for the acute inflammatory, coagulant and hemorrhagic action following snakebite. The local effects of snakebite envenomation by Bothrops species are particularly prevalent yet poorly studied, but include pain, edema, erythema, blistering, bleeding, and ecchymosis.

METHODS AND FINDINGS

In this study, we describe the dermatopathological findings observed in a series of 22 patients diagnosed with Bothrops envenomation treated in a tertiary hospital of Manaus, in the Brazilian Amazon. Clinically, pain and edema were observed in all patients, followed by fang marks (63.6%), secondary infection (36.3%), ecchymosis (31.8%), erythema (22.7%), blister (13.6%), and necrosis (4.5%). Regarding histopathological findings, epidermal alterations such as spongiosis, acanthosis and hyperkeratosis were the most observed characteristics in our cases series, with isolated cases of hyperplasia, hemorrhagic intraepidermal blister and severe necrosis. Changes in dermis and hypodermis consisted mainly of hemorrhage, inflammatory infiltrate, edema, congestion, and vascular damage, whereas cases of collagen damage, necrosis, abscess, and signs of tissue repair, indicated by the presence of granulation tissue, were also observed, with a persistence of inflammatory and hemostatic alterations even days after antivenom administration. Therefore, the tissue damage resulting from Bothrops envenomation could be related to both direct venom activity as well as inflammatory response or presence of infectious process. The histopathological analysis of human skin injury can enlighten the pathological and endogenous effects of local envenomation and could underpin new strategies, including novel treatments, adjuvants or changes in clinical management, that lead to better outcomes in snakebite patients.

Computational insight into the peptide-based inhibition of α-cobratoxin

Snakebite envenoming results in the death of thousands of people each year and has been classified as a neglected tropical disease by the World Health Organization (WHO). The toxins released into the bloodstream of the victim bind to the nicotinic acetylcholine receptor and restrict transmission of nerve impulses leading to paralysis and cardiac arrest. Conventional antibody-based treatments often have adverse side effects or are difficult to perform. Hence, efforts are underway to devise alternative forms of treatment that address these therapeutic shortcomings. Peptide-based inhibitors have recently gained attention due to their high specificity and ease of preparation. Here, we explore the mechanism of a peptide inhibitor of α-cobratoxin using all-atom molecular dynamics (MD) simulations. We also quantify the energetics of the toxin-peptide dissociation process using the non-equilibrium steered MD technique. Our study reveals that the inhibitor migrates close to Loop-II of α-cobratoxin and alters its dimerization tendency. From energy studies, we found that the peptide first binds to one unit of α-cobratoxin in a particular orientation, followed by the binding of a second toxin molecule, which effectively masks the residues that interact with the nicotinic acetylcholine receptor. Our work provides atomic-level insight into the inhibition process that can be utilized in the future design of inhibitors with superior binding capabilities.

Deciphering toxico-proteomics of Asiatic medically significant venomous snake species: A systematic review and interactive data dashboard

Snakebite envenomation (SBE) is a neglected tropical disease (NTD) with an approximate 1.8 million cases annually. The tremendous figure is concerning, and the currently available treatment for snakebite envenomation is antivenom. However, the current antivenom has limited cross-neutralisation activity due to the variations in snake venom composition across species and geographical locations. The proteomics of medically important venomous species is essential as they study the venom compositions within and among different species. The advancement of sophisticated proteomic approaches allows intensive investigation of snake venoms. Nevertheless, there is a need to consolidate the venom proteomics profiles and distribution analysis to examine their variability patterns. This review systematically analysed the proteomics and toxicity profiles of medically important venomous species from Asia across different geographical locations. An interactive dashboard - Asiatic Proteomics Interactive Datasets was curated to consolidate the distribution patterns of the venom compositions, serve as a comprehensive directory for large-scale comparative meta-analyses. The population proteomics demonstrate higher diversities in the predominant venom toxins. Besides, inter-regional differences were also observed in Bungarus sp., Naja sp., Calliophis sp., and Ophiophagus hannah venoms. The elapid venoms are predominated with three-finger toxins (3FTXs) and phospholipase A2 (PLA2). Intra-regional variation is only significantly observed in Naja naja venoms. Proteomics diversity is more prominent in viper venoms, with widespread dominance observed in snake venom metalloproteinase (SVMP) and snake venom serine protease (SVSP). Correlations exist between the proteomics profiles and the toxicity (LD50) of the medically important venomous species. Additionally, the predominant toxins, alongside their pathophysiological effects, were highlighted and discussed as well. The insights of interactive toxico-proteomics datasets provide comprehensive frameworks of venom dynamics and contribute to developing antivenoms for snakebite envenomation. This could reduce misdiagnosis of SBE and accelerate the researchers' data mining process.

Unravelling the enigma: Autopsy challenges in alleged snakebite deaths

Snakebites account for a substantial public health burden in India, contributing to 80 % of global snakebite fatalities. This case series explores the intricacies of two alleged neurotoxic snakebite deaths, delving into the complexities of diagnosing neurotoxic snakebite deaths in India through meticulous medico-legal autopsies. Despite initial suspicions and circumstantial evidence suggesting snakebite involvement, the autopsies revealed surprising causes of death. The article discusses challenges in accurately attributing deaths to snakebites, and the potential for false claims, and underscores the crucial role of Forensic pathologists in dispelling enigmas. Forensic pathologists are urged to maintain an unbiased approach, allowing postmortem findings to guide conclusions amidst deliberate attempts to mislead. The cases described highlight that ruling out snake bites in cases with positive history is as challenging as opining a case of neurotoxic snake bite as they are mainly the diagnosis of exclusion in autopsy.

Exploring the inhibitory potential of phytochemicals from Vernonia glaberrima leaves against snake venom toxins through computational simulation and experimental validation

Phospholipase A2 (PLA2) is an enzyme present in appreciable quantity in snake venoms which catalyze the hydrolysis of glycerophospholipids at sn-2 position and promote the release of lysophospholipids and fatty acids. 5-methylcoumarin-4-β-glucoside (5MC4BG) and lupeol were previously isolated from the leaves of V. glaberrima. The aim of this research was to evaluate effect of these compounds as potential inhibitors of snake venom toxins of Naja nigricollis using an in vitro and in silico studies. Antisnake venom studies was conducted using acidimetry while the molecular docking analysis against PLA2 enzyme from N. nigricollis was performed using Auto Dock Vina and ADME-Tox analysis was evaluated using swissADME and ProTox-II online servers. The two compounds (5MC4BG and Lupeol) were able to inhibit the hydrolytic actions of PLA2 enzyme with percentage inhibition ranging from 23.99 to 72.36 % and 21.97-24.82 % at 0.0625-1.00 mg/mL respectively while the standard ASV had 82.63 % at 1.00 mg/mL after 10 min incubation at 37 °C. Similar effects were observed after 30 min incubation, although there was significant increase in percentage inhibition of 5MC4BG and lupeol ranging from 66.51 to 83.73 % and 54.87-59.60 % at similar concentrations. Furthermore, the compounds were able to bind to the active site of PLA2 enzyme with high affinity (-7.7 to -6.3 kcal/mol); the standard ligand, Varespladib had a docking score of -6.9 kcal/mol and they exhibited favorable drug-likeness and pharmacokinetic properties and according to toxicity predictions, the two compounds are toxic. In conclusion, the leaf of V. glaberrima contains phytoconstituents with antisnake activity and thus, validates the hypothesis that, the phytoconstituents of V. glaberrima leaves has antisnake venom activity against N. nigricollis venom and thus, should be studied further for the development as antisnake venom agents.

Acute ischaemic stroke and deep vein thrombosis following snakebite

Snakebite envenomation remains a neglected tropical public health issue claiming thousands of lives every year. It is a common medical emergency and a threat to the impoverished populations of low-income and middle-income countries including India. A combination of ischaemic stroke and deep vein thrombosis is a devastating duo complication of snake bite, with no literature report to date. Here, the authors report an unusual case of a young woman developing ischaemic stroke and deep vein thrombosis following snakebite even after the use of antivenom. MRI brain showed right thalamic infarct with haemorrhagic transformation and, ultrasound Doppler revealed right lower limb deep vein thrombosis. The pathophysiology of deep vein thrombosis and ischaemic stroke is complex. It is believed that the activation of the coagulation cascade, complement system together with endothelial injury and immune activation leads to inflammation, thrombosis and occlusion of smaller and even larger vessels.

Evaluation of venom diversity and antivenom quality from the venom of long-term captive vs recently wild captured Pseudocerastes persicus snake: An In vitro and In vivo study

Snakebite envenomation is a life-threatening condition and antivenoms are used as the most effective treatment. Venom obtained from snakes in long-term captivity showed some variations in comparison to the venom of the wild snakes. The objective of this study is to compare the venom of the Pseudocerastes persicus under long-term captivity and wild conditions as well as the antivenom obtained from these venoms. We have analyzed venom samples and produced trivalent antivenoms using the venom of long-term captive (LTC) or recently wild-captured (RWC) Pseudocerastes persicus, and RWC Macrovipera lebetina, and Echis carinatus. The HPLC analysis revealed that the RWC snakes' venom had three peaks that were not present in the LTC snake's venom. Further analysis using MALDI-TOF and MS/MS showed that the fraction with a retention time (RT) of 14 min contained a toxin from the Kunitz-type serine protease inhibitor (KUT) class, while the fraction with RT 21 a peptide identified within the snake venom metalloproteinase (SVMP) class. The third peak was identified as a sphingolipid. Interestingly, the in vivo preclinical tests showed no significant differences in the effectiveness of the antivenoms. which could be due to the cross-immunogenicity or cross-reactivity between different toxins in the venom. According to our results, small variations in the venom composition of a species do not lead to a decrease in the efficacy of the polyvalent antivenom.

CTXP, The Major Cobra Toxin Peptide from Naja Naja Oxiana Venom; A Promising Target for Antivenom Agent Development

BACKGROUND AND OBJECTIVE

Snakebite envenoming is a serious public health issue causing more than 135,000 annual deaths worldwide. Naja Naja Oxiana is one of the most clinically important venomous snakes in Iran and Central Asia. Conventional animal-derived polyclonal antibodies are the major treatment of snakebite envenoming. Characterization of venom components helps to pinpoint the toxic protein responsible for clinical manifestations in victims, which aids us in developing efficient antivenoms with minimal side effects. Therefore, the present study aimed to identify the major lethal protein of Naja Naja Oxiana by top-down proteomics.

METHODS

Venom proteomic profiling was performed using gel filtration (GF), reversed-phase (RP) chromatography, and intact mass spectrometry. The toxicity of GF-, and RP-eluted fractions was analyzed in BALB/c mice. The rabbit polyclonal antisera were produced against crude venom, GF fraction V (FV), and RP peak 1 (CTXP) and applied in neutralization assays.

RESULTS

Toxicity studies in BALB/c identified FV as the major toxic fraction of venom. Subsequently, RP separation of FV resulted in eight peaks, of which peak 1, referred to as "CTXP" (cobra toxin peptide), was identified as the major lethal protein. In vivo neutralization assays using rabbit antisera showed that polyclonal antibodies raised against FV and CTXP are capable of neutralizing at least 2-LD50s of crude venom, FV, and CTXP in all tested mice.

CONCLUSION

Surprisingly, the Anti-CTXP antibody could neutralize 8-LD50 of the CTXP peptide. These results identified CTXP (a 7 kDa peptide) as a potential target for the development of novel efficient antivenom agents.

Unraveling snake venom phospholipase A2: an overview of its structure, pharmacology, and inhibitors

Snake bite is a neglected disease that affects millions of people worldwide. WHO reported approximately 5 million people are bitten by various species of snakes each year, resulting in nearly 1 million deaths and an additional three times cases of permanent disability. Snakes utilize the venom mainly for immobilization and digestion of their prey. Snake venom is a composition of proteins and enzymes which is responsible for its diverse pharmacological action. Snake venom phospholipase A2 (SvPLA2) is an enzyme that is present in every snake species in different quantities and is known to produce remarkable functional diversity and pharmacological action like inflammation, necrosis, myonecrosis, hemorrhage, etc. Arachidonic acid, a precursor to eicosanoids, such as prostaglandins and leukotrienes, is released when SvPLA2 catalyzes the hydrolysis of the sn-2 positions of membrane glycerophospholipids, which is responsible for its actions. Polyvalent antivenom produced from horses or lambs is the standard treatment for snake envenomation, although it has many drawbacks. Traditional medical practitioners treat snake bites using plants and other remedies as a sustainable alternative. More than 500 plant species from more than 100 families reported having venom-neutralizing abilities. Plant-derived secondary metabolites have the ability to reduce the venom's adverse consequences. Numerous studies have documented the ability of plant chemicals to inhibit the enzymes found in snake venom. Research in recent years has shown that various small molecules, such as varespladib and methyl varespladib, effectively inhibit the PLA2 toxin. In the present article, we have overviewed the knowledge of snake venom phospholipase A2, its classification, and the mechanism involved in the pathophysiology of cytotoxicity, myonecrosis, anticoagulation, and inflammation clinical application and inhibitors of SvPLA2, along with the list of studies carried out to evaluate the potency of small molecules like varespladib and secondary metabolites from the traditional medicine for their anti-PLA2 effect.

The concept of Big Four: Road map from snakebite epidemiology to antivenom efficacy

Snake envenomation is a life-threatening disease caused by the injection of venom toxins from the venomous snake bite. Snakebite is often defined as the occupational or domestic hazard mostly affecting the rural population. India experiences a high number of envenoming cases and fatality due to the nation's diversity in inhabiting venomous snakes. The Indian Big Four snakes namely Russell's viper (Daboia russelii), spectacled cobra (Naja naja), common krait (Bungarus caeruleus), and saw-scaled viper (Echis carinatus) are responsible for majority of the snake envenoming cases and death. The demographic characteristics including occupation, stringent snake habitat management, poor healthcare facilities and ignorance of the rural victims are the primary influencers of high mortality. Biogeographic venom variation greatly influences the clinical pathologies of snake envenomation. The current antivenoms against the Big Four snakes are found to be less immunogenic against the venom toxins emphasizing the necessity of alternative approaches for antivenom generation. This review summarizes the burden of snake envenomation in India by the Big Four snakes including the geographic distribution of snake species and biogeographic venom variation. We have provided comprehensive information on snake venom proteomics that has aided the better understanding of venom induced pathological features, summarized the impact of current polyvalent antivenom therapy highlighting the need for potential antivenom treatment for the effective management of snakebites.

Current Insights in the Mechanisms of Cobra Venom Cytotoxins and Their Complexes in Inducing Toxicity: Implications in Antivenom Therapy

Cytotoxins (CTXs), an essential class of the non-enzymatic three-finger toxin family, are ubiquitously present in cobra venoms. These low-molecular-mass toxins, contributing to about 40 to 60% of the cobra venom proteome, play a significant role in cobra venom-induced toxicity, more prominently in dermonecrosis. Structurally, CTXs contain the conserved three-finger hydrophobic loops; however, they also exhibit a certain degree of structural diversity that dictates their biological activities. In their mechanism, CTXs mediate toxicity by affecting cell membrane structures and membrane-bound proteins and activating apoptotic and necrotic cell death pathways. Notably, some CTXs are also responsible for depolarizing neurons and heart muscle membranes, thereby contributing to the cardiac failure frequently observed in cobra-envenomed victims. Consequently, they are also known as cardiotoxins (CdTx). Studies have shown that cobra venom CTXs form cognate complexes with other components that potentiate the toxic effects of the venom's individual component. This review focuses on the pharmacological mechanism of cobra venom CTXs and their complexes, highlighting their significance in cobra venom-induced pathophysiology and toxicity. Furthermore, the potency of commercial antivenoms in reversing the adverse effects of cobra venom CTXs and their complexes in envenomed victims has also been discussed.

Equatorial Spitting Cobra (Naja sumatrana) from Malaysia (Negeri Sembilan and Penang), Southern Thailand, and Sumatra: Comparative Venom Proteomics, Immunoreactivity and Cross-Neutralization by Antivenom

The Equatorial Spitting Cobra (Naja sumatrana) is a medically important venomous snake species in Southeast Asia. Its wide geographical distribution implies potential intra-specific venom variation, while there is no species-specific antivenom available to treat its envenoming. Applying a protein-decomplexing proteomic approach, the study showed that three-finger toxins (3FTX), followed by phospholipases A₂ (PLA₂), were the major proteins well-conserved across N. sumatrana venoms of different locales. Variations were noted in the subtypes and relative abundances of venom proteins. Of note, alpha-neurotoxins (belonging to 3FTX) are the least in the Penang specimen (Ns-PG, 5.41% of total venom proteins), compared with geographical specimens from Negeri Sembilan (Ns-NS, 14.84%), southern Thailand (Ns-TH, 16.05%) and Sumatra (Ns-SU, 10.81%). The alpha-neurotoxin abundance, in general, correlates with the venom’s lethal potency. The Thai Naja kaouthia Monovalent Antivenom (NkMAV) was found to be immunoreactive toward the N. sumatrana venoms and is capable of cross-neutralizing N. sumatrana venom lethality to varying degrees (potency = 0.49–0.92 mg/mL, interpreted as the amount of venom completely neutralized per milliliter of antivenom). The potency was lowest against NS-SU venom, implying variable antigenicity of its lethal alpha-neurotoxins. Together, the findings suggest the para-specific and geographical utility of NkMAV as treatment for N. sumatrana envenoming in Southeast Asia.

Australian Sea Snake Envenoming Causes Myotoxicity and Non-Specific Systemic Symptoms - Australian Snakebite Project (ASP-24)

Background: Sea snakes are venomous snakes found in the warm parts of the Indo-Pacific, including around Australia. Most sea snake envenoming causes myotoxicity, but previous Australian case reports describe neurotoxicity. We aimed to describe the epidemiology and clinical presentation of Australian sea snake envenoming and the effectiveness of antivenom.

Methods: Patients were recruited to the Australian Snakebite Project (ASP), an Australia-wide prospective observational study recruiting all patients with suspected or confirmed snakebite >2 years. Information about demographics, bite circumstances, species involved, clinical and laboratory features of envenoming, and treatment is collected and entered into a purpose-built database.

Results: Between January 2002 and August 2020, 13 patients with suspected sea snake bite were recruited to ASP, 11 were male; median age was 30 years. Bites occurred in Queensland and Western Australia. All patients were in or around, coastal waters at the time of bite. The species involved was identified in two cases (both Hydrophis zweifeli). Local effects occurred in 9 patients: pain (5), swelling (5), bleeding (2), bruising (1). Envenoming occurred in eight patients and was characterised by non-specific systemic features (6) and myotoxicity (2). Myotoxicity was severe (peak CK 28200 and 48100 U/L) and rapid in onset (time to peak CK 13.5 and 15.1 h) in these two patients. Non-specific systemic features included nausea (6), headache (6), abdominal pain (3), and diaphoresis (2). Leukocytosis, neutrophilia, and lymphopenia occurred in both patients with myotoxicity and was evident on the first blood test. No patients developed neurotoxicity or coagulopathy. Early Seqirus antivenom therapy was associated with a lower peak creatine kinase.

Conclusion: While relatively rare, sea snake envenoming is associated with significant morbidity and risk of mortality. Early antivenom appears to have a role in preventing severe myotoxicity and should be a goal of therapy.

Splenic rupture and subsequent splenectomy in a young healthy victim following Russell's viper bite

Splenic rupture and/or splenectomy is/are not uncommon in clinical arena. Here we present this case of extensive haemorrhage-induced splenic rupture which resulted in splenectomy in a young healthy male (who did not have any previous medical conditions) following a Russell's viper bite. He developed upper abdominal and shoulder pain on his left side along with hypotension and reduced level of haemoglobin on the third day following bite despite antivenom treatment. Following confirmation of splenic rupture and haemoperitoneum by ultrasound and computed tomography scans, an emergency splenectomy was performed using laparotomy. Although Russell's viper bites are known to induce bleeding complications, splenic rupture due to haemorrhage in spleen has not been previously reported. Russell's viper venom toxins such as metalloproteases, serine proteases and phospholipase A2 might have affected the vascular permeability resulting in excessive bleeding and increased pressure in the spleen leading to rupture. Further investigations are required to underpin the impact of snake venom toxins on the architecture and functions of spleen. However, the clinicians who treat snakebites should be aware of this type of rare complications so as to provide appropriate management for such victims.

De Novo Venom-Gland Transcriptomics of Spine-Bellied Sea Snake (Hydrophis curtus) from Penang, Malaysia-Next-Generation Sequencing, Functional Annotation and Toxinological Correlation

Envenomation resulted from sea snake bite is a highly lethal health hazard in Southeast Asia. Although commonly caused by sea snakes of Hydrophiinae, each species is evolutionarily distinct and thus, unveiling the toxin gene diversity within individual species is important. Applying next-generation sequencing, this study investigated the venom-gland transcriptome of Hydrophis curtus (spine-bellied sea snake) from Penang, West Malaysia. The transcriptome was de novo assembled, followed by gene annotation and sequence analyses. Transcripts with toxin annotation were only 96 in number but highly expressed, constituting 48.18% of total FPKM in the overall transcriptome. Of the 21 toxin families, three-finger toxins (3FTX) were the most abundantly expressed and functionally diverse, followed by phospholipases A₂. Lh_FTX001 (short neurotoxin) and Lh_FTX013 (long neurotoxin) were the most dominant 3FTXs expressed, consistent with the pathophysiology of envenomation. Lh_FTX001 and Lh_FTX013 were variable in amino acid compositions and predicted epitopes, while Lh_FTX001 showed high sequence similarity with the short neurotoxin from Hydrophis schistosus, supporting cross-neutralization effect of Sea Snake Antivenom. Other toxins of low gene expression, for example, snake venom metalloproteinases and L-amino acid oxidases not commonly studied in sea snake venom were also identified, enriching the knowledgebase of sea snake toxins for future study.