Biogeographic venom variation in Russell's viper (Daboia russelii) and the preclinical inefficacy of antivenom therapy in snakebite hotspots

Pulmonary Thromboembolism following Russell's Viper Bites

Snakebite envenoming and its resulting complications are serious threats to the health of vulnerable people living in rural areas of developing countries. The knowledge of the heterogeneity of symptoms associated with snakebite envenoming and their management strategies is vital to treat such life-threatening complications to save lives. Russell's viper envenomation induces a diverse range of clinical manifestations from commonly recognised haemotoxic and local effects to several rare conditions that are often not reported. The lack of awareness about these unusual manifestations can affect prompt diagnosis, appropriate therapeutic approaches, and positive outcomes for patients. Here, we report pulmonary thromboembolism that developed in three patients following Russell's viper envenomation and demonstrate their common clinical features and diagnostic and therapeutic approaches used. All patients showed clinical signs of local (oedema) and systemic (blood coagulation disturbances) envenomation, which were treated using polyvalent antivenom. They exhibited elevated heart rates, breathlessness, and reduced oxygen saturation, which are non-specific but core parameters in the diagnosis of pulmonary embolism. The recognition of pulmonary embolism was also achieved by an electrocardiogram, which showed sinus tachycardia and computed tomography and echocardiogram scans further confirmed this condition. Anti-coagulant treatment using low-molecular-weight heparin offered clinical benefits in these patients. In summary, this report reinforces the broad spectrum of previously unreported consequences of Russell's viper envenomation. The constant updating of healthcare professionals and the dissemination of major lessons learned in the clinical management of snakebite envenoming through scientific documentation and educational programs are necessary to mitigate the adverse impacts of venomous snakebites in vulnerable communities.

Indian green pit vipers: A lesser-known snake group of north-east India

Green pit vipers are one of the most widely distributed group of venomous snakes in south-east Asia. In Indian, green pit vipers are found in the Northern and North-eastern states spreading across eastern and central India and one of the lesser studied venoms. High morphological similarity among them has been a long-established challenge for species identification, however, a total of six species of Indian green pit viper belonging to genus Trimeresurus, Popeia and Viridovipera has been reported from North-east India. Biochemical and biological studies have revealed that venom exhibits substantial variation in protein expression level along with functional variability. The symptoms of envenomation are painful swelling at bite site, bleeding, necrosis along with systemic toxicity such as prolonged coagulopathy. Clinical data of green pit viper envenomated patients from Demow community health centre, Assam advocated against the use of Indian polyvalent antivenom pressing the need for a suitable antivenom for the treatment of green pit viper envenomation. To design effective and specific antivenom for green pit vipers, unveiling the proteome profile of these snakes is needed. In this study, a comparative venomic of green pit vipers of Northern and North-eastern India, their clinical manifestation as well as treatment protocol has been reviewed.

Immunoreactivity and neutralization efficacy of Pakistani Viper Antivenom (PVAV) against venoms of Saw-scaled Vipers (Echis carinatus subspp.) and Western Russell's Vipers (Daboia russelii) from the Indian subcontinent

Snakebite envenoming (SBE) is a priority Neglected Tropical Disease listed by the World Health Organization. South Asia is heavily affected, and virtually all countries in the region import polyvalent antivenom products from India for clinical use. The imported antivenoms, however, have suboptimal effectiveness due to geographical venom variation. Recently, a domestic bivalent product, named Pakistani Viper Antivenom (PVAV) has been developed specifically for Pakistani vipers, Echis carinatus sochureki and Daboia russelii. As a bivalent viperid antivenom, it is unknown yet if PVAV exhibits higher immunological binding and neutralization activities against viper venoms from distant locales compared with polyvalent antivenoms manufactured in India. This study thus examined the preclinical efficacy of PVAV against venoms of Western Russell's Vipers and Saw-scaled Viper subspecies from selected locales in the Indian subcontinent. PVAV generally outperformed the commonly used VINS polyvalent antivenom (VPAV, manufactured in India) in binding toward venoms, and showed superior or comparable neutralization efficacy against the venom procoagulant and hemorrhagic effects of Saw-scaled Vipers as well as Russell's Vipers from Pakistan and Sri Lanka. Based on normalized potency values, PVAV is far more potent than VPAV in neutralizing the lethality of all viper venoms, except that of the Indian Russell's Viper. The study shows conserved antigenicity of toxins responsible for major toxicity across these viperid venoms, and suggests the feasible production of a viper-specific antivenom with higher potency and broader geographical utility for the region.

Systematic review and meta-analysis on the efficacy of Indian polyvalent antivenom against the Indian snakes of clinical significance

Snakebite in India is a severe problem as it causes a mortality rate of 58,000 and a disability rate of 140,000 every year which is the highest among any other country. Antivenom is the primary therapy for snakebite, and its manufacturing techniques have essentially stayed unaltered for over a century. Indian polyvalent antivenom, a scientifically validated medicine for treating the toxic effects of snakebites, is available against the venom of the so-called Big Four snakes namely Spectacled cobra (Naja naja), Saw-scaled viper (Echis carinatus), Russell's viper (Daboia russelli) and the Common krait (Bungarus caeruleus), responsible for majority of the deaths in India. India hosts many other species of snakes, including cobras, kraits, saw-scaled vipers, sea snakes, and pit vipers, responsible for clinically severe envenomation. Neutralization strategy has been applied to access the efficacy of antivenoms, crucial for reducing snake bite deaths and disabilities. This review aims to conduct a systematic review and meta-analysis on the neutralization efficiency of the Polyvalent Antivenom (PAV) and focus on the factors that may contribute to the poor recognition of the antivenom towards the venom toxins. Reports focusing on the investigation of antivenom efficacy were searched and collected from several databases. Preclinical studies that reported the neutralization efficacy of the commercial antivenom against the medically important snakes of India were included. The articles were screened based on the inclusion criteria and 8 studies were shortlisted for meta-analysis. Pooled proportion was calculated for the antivenom efficacy reported by the studies and was found to be statistically significant with a 95% confidence interval. The heterogenicity in the venom toxicity and neutralization potency of the antivenom was evident in the overall estimate (proportion) and individual data. We provide comprehensive evidence on antivenom efficacy against medically important snakes from various parts of India which may aid in identifying the gaps in snake envenomation therapy and the need for novel potentially improved treatment of snakebites.

Optimizing drug discovery for snakebite envenoming via a high-throughput phospholipase A2 screening platform

Snakebite envenoming is a neglected tropical disease that causes as many as 1.8 million envenomings and 140,000 deaths annually. To address treatment limitations that exist with current antivenoms, the search for small molecule drug-based inhibitors that can be administered as early interventions has recently gained traction. Snake venoms are complex mixtures of proteins, peptides and small molecules and their composition varies substantially between and within snake species. The phospholipases A2 (PLA2) are one of the main pathogenic toxin classes found in medically important viper and elapid snake venoms, yet varespladib, a drug originally developed for the treatment of acute coronary syndrome, remains the only PLA2 inhibitor shown to effectively neutralise venom toxicity in vitro and in vivo, resulting in an extremely limited drug portfolio. Here, we describe a high-throughput drug screen to identify novel PLA2 inhibitors for repurposing as snakebite treatments. We present method optimisation of a 384-well plate, colorimetric, high-throughput screening assay that allowed for a throughput of ∼2,800 drugs per day, and report on the screening of a ∼3,500 post-phase I repurposed drug library against the venom of the Russell's viper, Daboia russelii. We further explore the broad-spectrum inhibitory potential and efficacy of the resulting top hits against a range of medically important snake venoms and demonstrate the utility of our method in determining drug EC50s. Collectively, our findings support the future application of this method to fully explore the chemical space to discover novel PLA2-inhibiting drugs of value for preventing severe pathology caused by snakebite envenoming.

The Need for Next-Generation Antivenom for Snakebite Envenomation in India

The limitations posed by currently available antivenoms have emphasized the need for alternative treatments to counteract snakebite envenomation. Even though exact epidemiological data are lacking, reports have indicated that most global snakebite deaths are reported in India. Among the many problems associated with snakebite envenomation, issues related to the availability of safer and more efficient antivenoms are of primary concern. Since India has the highest number of global snakebite deaths, efforts should be made to reduce the burden associated with snakebite envenoming. Alternative methods, including aptamers, camel antivenoms, phage display techniques for generating high-affinity antibodies and antibody fragments, small-molecule inhibitors, and natural products, are currently being investigated for their effectiveness. These alternative methods have shown promise in vitro, but their in vivo effectiveness should also be evaluated. In this review, the issues associated with Indian polyvalent antivenoms in neutralizing venom components from geographically distant species are discussed in detail. In a nutshell, this review gives an overview of the current drawbacks of using animal-derived antivenoms and several alternative strategies that are currently being widely explored.

Identifying the geographic distribution pattern of venomous snakes and regions of high snakebite risk in Iran

We describe species richness patterns of venomous snakes in Iran in order to produce snakebite risk prediction maps and identify gaps in regional health care centers capable of managing snakebites. We digitized distribution maps from the literature, Global Biodiversity Information Facility (GBIF), and the results of our own field studies of 24 terrestrial venomous snake species (including 4 endemic to Iran). Species richness patterns were associated with eight environmental factors. The variables have been extracted from the WorldClim dataset (bio12 = annual precipitation, bio15 = precipitation seasonality, bio17 = precipitation of the driest quarter, bio2 = mean diurnal range, bio3 = isothermality (bio2/bio7), bio4 = temperature seasonality, bio9 = mean temperature of the driest quarter and slope). Based on spatial analyses, species richness in Iran is highly affected by three environmental variables (bio12, 15, and 17) associated with precipitation. The relationship patterns among these predictors and species richness were strong and linear. The hotspot regions for venomous snakes species are concentrated on the western to southwestern and north to northeastern regions of Iran, which is partially consistent with the known Irano-Anatolian biodiversity hotspot. Because of the high number of endemic species and climatic conditions on the Iranian Plateau, the venoms of snakes distributed in those areas may contain novel properties and components.

Fangs in the Ghats: Preclinical Insights into the Medical Importance of Pit Vipers from the Western Ghats

The socioeconomic impact of snakebites in India is largely attributed to a subset of snake species commonly known as the 'big four'. However, envenoming by a range of other clinically important yet neglected snakes, a.k.a. the 'neglected many', also adds to this burden. The current approach of treating bites from these snakes with the 'big four' polyvalent antivenom is ineffective. While the medical significance of various species of cobras, saw-scaled vipers, and kraits is well-established, the clinical impact of pit vipers from regions such as the Western Ghats, northeastern India, and the Andaman and Nicobar Islands remains poorly understood. Amongst the many species of snakes found in the Western Ghats, the hump-nosed (Hypnale hypnale), Malabar (Craspedocephalus malabaricus), and bamboo (Craspedocephalus gramineus) pit vipers can potentially inflict severe envenoming. To evaluate the severity of toxicity inflicted by these snakes, we characterised their venom composition, biochemical and pharmacological activities, and toxicity- and morbidity-inducing potentials, including their ability to damage kidneys. Our findings highlight the therapeutic inadequacies of the Indian and Sri Lankan polyvalent antivenoms in neutralising the local and systemic toxicity resulting from pit viper envenomings.

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.

Unraveling the Reaction Mechanism of Russell's Viper Venom Factor X Activator: A Paradigm for the Reactivity of Zinc Metalloproteinases?

Snake venom metalloproteinases (SVMPs) are important drug targets against snakebite envenoming, the neglected tropical disease with the highest mortality worldwide. Here, we focus on Russell's viper (Daboia russelii), one of the "big four" snakes of the Indian subcontinent that, together, are responsible for ca. 50,000 fatalities annually. The "Russell's viper venom factor X activator" (RVV-X), a highly toxic metalloproteinase, activates the blood coagulation factor X (FX), leading to the prey's abnormal blood clotting and death. Given its tremendous public health impact, the WHO recognized an urgent need to develop efficient, heat-stable, and affordable-for-all small-molecule inhibitors, for which a deep understanding of the mechanisms of action of snake's principal toxins is fundamental. In this study, we determine the catalytic mechanism of RVV-X by using a density functional theory/molecular mechanics (DFT:MM) methodology to calculate its free energy profile. The results showed that the catalytic process takes place via two steps. The first step involves a nucleophilic attack by an in situ generated hydroxide ion on the substrate carbonyl, yielding an activation barrier of 17.7 kcal·mol^-1, while the second step corresponds to protonation of the peptide nitrogen and peptide bond cleavage with an energy barrier of 23.1 kcal·mol^-1. Our study shows a unique role played by Zn²⁺ in catalysis by lowering the pK_a of the Zn²⁺-bound water molecule, enough to permit the swift formation of the hydroxide nucleophile through barrierless deprotonation by the formally much less basic Glu140. Without the Zn²⁺ cofactor, this step would be rate-limiting.

Peripheral Arterial Thrombosis following Russell's Viper Bites

Envenomings by Russell's viper ( Daboia russelii ), a species of high medical importance in India and other Asian countries, commonly result in hemorrhage, coagulopathies, necrosis, and acute kidney injury. Although bleeding complications are frequently reported following viper envenomings, thrombotic events occur rarely (reported only in coronary and carotid arteries) with serious consequences. For the first time, we report three serious cases of peripheral arterial thrombosis following Russell's viper bites and their diagnostic, clinical management, and mechanistic insights. These patients developed occlusive thrombi in their peripheral arteries and symptoms despite antivenom treatment. In addition to clinical features, computed tomography angiography was used to diagnose arterial thrombosis and ascertain its precise locations. They were treated using thrombectomy or amputation in one case that presented with gangrenous digits. Mechanistic insights into the pathology through investigations revealed the procoagulant actions of Russell's viper venom in standard clotting tests as well as in rotational thromboelastometry analysis. Notably, Russell's viper venom inhibited agonist-induced platelet activation. The procoagulant effects of Russell's viper venom were inhibited by a matrix metalloprotease inhibitor, marimastat, although a phospholipase A 2 inhibitor (varespladib) did not show any inhibitory effects. Russell's viper venom induced pulmonary thrombosis when injected intravenously in mice and thrombi in the microvasculature and affected skeletal muscle when administered locally. These data emphasize the significance of peripheral arterial thrombosis in snakebite victims and provide awareness, mechanisms, and robust strategies for clinicians to tackle this issue in patients.

Clinical aspects of snakebite envenoming and its treatment in low-resource settings

There is increasing recognition of the public health importance of snakebite envenoming. Worldwide annual incidence is likely to be 5 million bites, with mortality exceeding 150 000 deaths, and the resulting physical and psychological morbidity leads to substantial social and economic repercussions. Prevention through community education by trained health workers is the most effective and economically viable strategy for reducing risk of bites and envenoming. Clinical challenges to effective treatment are most substantial in rural areas of low-resource settings, where snakebites are most common. Classic skills of history taking, physical examination, and use of affordable point-of-care tests should be followed by monitoring of evolving local and systemic envenoming. Despite the profusion of new ideas for interventions, hyperimmune equine or ovine plasma-derived antivenoms remain the only specific treatment for snakebite envenoming. The enormous interspecies and intraspecies complexity and diversity of snake venoms, revealed by modern venomics, demands a radical redesign of many current antivenoms.

The Effectiveness of Antibiotics in Managing Bacterial Infections on Bite Sites following Snakebite Envenomation

Snakebite envenomation (SBE) is a life-threatening medical emergency with a high mortality rate. Common secondary complications following SBE, such as wound infections, are significant due to their impact on worsening local tissue damage and causing systemic infection. Antivenoms are not effective to treat wound infections following SBE. Moreover, in several rural clinical settings, broad-spectrum antibiotics are often used without clear guidelines or based on limited laboratory data, resulting in undesirable side effects and exacerbated treatment costs. Therefore, robust antibiotic strategies should be developed to tackle this critical issue. Currently, there is limited information available on the bacterial profiles of SBE-induced infections and antibiotic susceptibility. Hence, it is essential to improve the knowledge of bacterial profiles and their antibiotic sensitivity in SBE victims to develop better treatment strategies. This study aimed to address this issue by examining the bacterial profiles of SBE victims with a specific focus on Russell's viper envenomation. The most frequently found bacteria in the bites of SBE victims were Staphylococcus aureus, Klebsiella sp., Escherichia coli, and Pseudomonas aeruginosa. Linezolid, clindamycin, colistin, meropenem, and amikacin were some of the most effective antibiotics for commonly grown bacteria in SBE victims. Similarly, ciprofloxacin, ampicillin, amoxiclave, cefixime, and tetracyclin were the least effective antibiotics for common bacteria found in the wound swabs of SBE victims. These data provide robust guidance for infection management following SBE and offer useful insights to aid in designing effective treatment protocols for SBE with serious wound infections in rural areas where laboratory facilities may not be readily available.

Russell's viper envenomation induces rectus sheath haematoma

Snakebite envenomation causes systemic and local manifestations, which result from the individual or synergistic actions of multiple venom components. The pathological hallmarks of medically important venomous snakes such as the Indian Russell's viper (Daboia russelii) are well known. Envenomation by Russell's viper is typically characterised by coagulopathies, muscular damage, nephrotoxicity, and neurotoxicity. However, recent reports have revealed several unusual complications that provide a better understanding of Russell's viper envenomation effects. To further strengthen this, here, we report a case of Russell's viper bite that induced acute abdominal pain, which was intensified on day two and conservatively treated under medical supervision. Both Fothergill and Carnett signs were positive for this patient. An ultrasound imaging revealed a dissimilar dense mass, and the abdominal computed tomography scan confirmed rectus sheath haematoma. The clinical management involved the administration of polyvalent antivenom, packed red blood cells, fresh frozen plasma, and platelets. The patient recovered gradually and was discharged from the hospital eight days after the bite. Overall, this case presentation shares an uncommon experience and adds new insights into the complex series of rare pathological events associated with Russell's viper bites in India. The scientific documentation of relatively infrequent entities based on an ongoing living assessment of medical experiences, for example, this rectus sheath haematoma, constitutes valuable guidance for an adequate diagnosis and timely treatment. Essential awareness among clinicians and further research on understanding the molecular relationship between Russell's viper venom and rectus sheath haematoma will improve patient outcomes and understanding of this condition, respectively.

Children and Snakebite: Snake Venom Effects on Adult and Paediatric Plasma

Snakebite is a globally neglected tropical disease, with coagulation disturbances being the primary pathology of many deadly snake venoms. Age-related differences in human plasma have been abundantly reported, yet the effect that these differences pose regarding snakebite is largely unknown. We tested for differences in coagulotoxic effects (via clotting time) of multiple snake venoms upon healthy human adult (18+) and paediatric (median 3.3 years old) plasma in vivo and compared these effects to the time it takes the plasmas to clot without the addition of venom (the spontaneous clotting time). We tested venoms from 15 medically significant snake species (from 13 genera) from around the world with various mechanisms of coagulotoxic actions, across the three broad categories of procoagulant, pseudo-procoagulant, and anticoagulant, to identify any differences between the two plasmas in their relative pathophysiological vulnerability to snakebite. One procoagulant venom (Daboia russelii, Russell's Viper) produced significantly greater potency on paediatric plasma compared with adult plasma. In contrast, the two anticoagulant venoms (Pseudechis australis, Mulga Snake; and Bitis cornuta, Many-horned Adder) were significantly more potent on adult plasma. All other procoagulant venoms and all pseudo-procoagulant venoms displayed similar potency across both plasmas. Our preliminary results may inform future studies on the effect of snake venoms upon plasmas from different age demographics and hope to reduce the burden of snakebite upon society.

The deep-rooted origin of disulfide-rich spider venom toxins

Spider venoms are a complex concoction of enzymes, polyamines, inorganic salts, and disulfide-rich peptides (DRPs). Although DRPs are widely distributed and abundant, their bevolutionary origin has remained elusive. This knowledge gap stems from the extensive molecular divergence of DRPs and a lack of sequence and structural data from diverse lineages. By evaluating DRPs under a comprehensive phylogenetic, structural and evolutionary framework, we have not only identified 78 novel spider toxin superfamilies but also provided the first evidence for their common origin. We trace the origin of these toxin superfamilies to a primordial knot - which we name 'Adi Shakti', after the creator of the Universe according to Hindu mythology - 375 MYA in the common ancestor of Araneomorphae and Mygalomorphae. As the lineages under evaluation constitute nearly 60% of extant spiders, our findings provide fascinating insights into the early evolution and diversification of the spider venom arsenal. Reliance on a single molecular toxin scaffold by nearly all spiders is in complete contrast to most other venomous animals that have recruited into their venoms diverse toxins with independent origins. By comparatively evaluating the molecular evolutionary histories of araneomorph and mygalomorph spider venom toxins, we highlight their contrasting evolutionary diversification rates. Our results also suggest that venom deployment (e.g. prey capture or self-defense) influences evolutionary diversification of DRP toxin superfamilies.

Epidemiological, clinical and hematobiochemical studies on hemotoxic snakebite in bovines

Snakebite is a conflict between venomous snakes and humans as well as livestock and considered as neglected tropical disease. The present study aimed to investigate the hospital prevalence, clinical and hemato-biochemical aspects of hemotoxic snakebite in bovines. The overall hospital prevalence of hemotoxic snakebite in bovines was found to be 0.93%. Highest prevalence of hemotoxic snakebite in bovines was observed in August month during monsoon season in female bovines with higher cases in buffaloes. The highest occurrence was reported in native Marathwadi buffalo, non-descript and Deoni cattle of > 4 years and 1-4 years age group in forelimbs and hindlimbs during morning and evening hours. Ascending swelling over limbs extending upward and lameness in case of bite on limbs while asymmetrical swelling in case of bite over face, occasional signs of bleeding like melena, hematuria, epistaxis and bleeding from the site of bite were the prominent clinical signs observed in hemotoxic snakebite affected bovines. Highly significant increase in heart rate and respiration rate, while decrease in rumen motility was observed in snakebite affected bovines. Hemato-biochemial analysis showed highly significant increase in leukocyte count, erythrocyte count and PCV, significant increase in granulocyte and monocyte count, highly significant decrease in platelet count while increase in capillary blood clotting time, bilirubin, blood urea nitrogen, creatinine, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase and creatine kinase levels compared to healthy bovines.

Highly Evolvable: Investigating Interspecific and Intraspecific Venom Variation in Taipans (Oxyuranus spp.) and Brown Snakes (Pseudonaja spp.)

Snake venoms are complex mixtures of toxins that differ on interspecific (between species) and intraspecific (within species) levels. Whether venom variation within a group of closely related species is explained by the presence, absence and/or relative abundances of venom toxins remains largely unknown. Taipans (Oxyuranus spp.) and brown snakes (Pseudonaja spp.) represent medically relevant species of snakes across the Australasian region and provide an excellent model clade for studying interspecific and intraspecific venom variation. Using liquid chromatography with ultraviolet and mass spectrometry detection, we analyzed a total of 31 venoms covering all species of this monophyletic clade, including widespread localities. Our results reveal major interspecific and intraspecific venom variation in Oxyuranus and Pseudonaja species, partially corresponding with their geographical regions and phylogenetic relationships. This extensive venom variability is generated by a combination of the absence/presence and differential abundance of venom toxins. Our study highlights that venom systems can be highly dynamical on the interspecific and intraspecific levels and underscores that the rapid toxin evolvability potentially causes major impacts on neglected tropical snakebites.

Commercial Antivenoms Exert Broad Paraspecific Immunological Binding and In Vitro Inhibition of Medically Important Bothrops Pit Viper Venoms

Snakebite envenoming is a life threatening neglected tropical disease that represents a considerable public health concern in the tropics. Viperid snakes of the genus Bothrops are among those of greatest medical importance in Latin America, and they frequently cause severe systemic haemotoxicity and local tissue destructive effects in human victims. Although snakebite antivenoms can be effective therapeutics, their efficacy is undermined by venom toxin variation among snake species. In this study we investigated the extent of paraspecific venom cross-reactivity exhibited by three distinct anti-Bothrops antivenoms (Soro antibotrópico-crotálico, BothroFav and PoliVal-ICP) against seven different Bothrops pit viper venoms from across Latin America. We applied a range of in vitro assays to assess the immunological binding and recognition of venom toxins by the antivenoms and their inhibitory activities against specific venom functionalities. Our findings demonstrated that, despite some variations, the monovalent antivenom BothroFav and the polyvalent antivenoms Soro antibotrópico-crotálico and PoliVap-ICP exhibited extensive immunological recognition of the distinct toxins found in the different Bothrops venoms, with Soro antibotrópico-crotálico generally outperformed by the other two products. In vitro functional assays revealed outcomes largely consistent with the immunological binding data, with PoliVap-ICP and BothroFav exhibiting the greatest inhibitory potencies against procoagulant and fibrinogen-depleting venom activities, though Soro antibotrópico-crotálico exhibited potent inhibition of venom metalloproteinase activities. Overall, our findings demonstrate broad levels of antivenom paraspecificity, with in vitro immunological binding and functional inhibition often highly comparable between venoms used to manufacture the antivenoms and those from related species, even in the case of the monovalent antivenom BothroFav. Our findings suggest that the current clinical utility of these antivenoms could possibly be expanded to other parts of Latin America that currently suffer from a lack of specific snakebite therapies.

Stings on wings: Proteotranscriptomic and biochemical profiling of the lesser banded hornet (Vespa affinis) venom

Distinct animal lineages have convergently recruited venoms as weaponry for prey capture, anti-predator defence, conspecific competition, or a combination thereof. Most studies, however, have been primarily confined to a narrow taxonomic breadth. The venoms of cone snails, snakes, spiders and scorpions remain particularly well-investigated. Much less explored are the venoms of wasps (Order: Hymenoptera) that are infamous for causing excruciating and throbbing pain, justifying their apex position on Schmidt's pain index, including some that are rated four on four. For example, the lesser banded wasp (V. affinis) is clinically important yet has only been the subject of a few studies, despite being commonly found across tropical and subtropical Asia. Stings from these wasps, especially from multiple individuals of a nest, often lead to clinically severe manifestations, including mastocytosis, myasthenia gravis, optic neuropathy, and life-threatening pathologies such as myocardial infarction and organ failure. However, their venom composition and activity remain unexplored in the Indian subcontinent. Here, we report the proteomic composition, transcriptomic profile, and biochemical and pharmacological activities of V. affinis venom from southern India. Our findings suggest that wasp venoms are rich in diverse toxins that facilitate antipredator defence. Biochemical and pharmacological assessments reveal that these toxins can exhibit significantly higher activities than their homologues in medically important snakes. Their ability to exert potent effects on diverse molecular targets makes them a treasure trove for discovering life-saving therapeutics. Fascinatingly, wasp venoms, being evolutionarily ancient, exhibit a greater degree of compositional and sequence conservation across very distant populations/species, which contrasts with the patterns of venom evolution observed in evolutionarily younger lineages, such as advanced snakes and cone snails.

The Middle Eastern Cousin: Comparative Venomics of Daboia palaestinae and Daboia russelii

Among the medically most important snakes in the world, the species belonging to the genus Daboia have been attributed to the highest number of human envenomings, deaths and disabilities. Given their significant clinical relevance, the venoms of Russell's vipers (D. russelii and D. siamensis) have been the primary focus of research. In contrast, the composition, activity, ecology and evolution of venom of its congener, the Palestine viper (D. palaestinae), have remained largely understudied. Therefore, to unravel the factors responsible for the enhanced medical relevance of D. russelii in comparison to D. palaestinae, we comparatively evaluated their venom proteomes, biochemical activities, and mortality and morbidity inflicting potentials. Furthermore, the synthesis and regulation of venom in snakes have also remained underinvestigated, and the relative contribution of each venom gland remains unclear. We address this knowledge gap by sequencing the tissue transcriptomes of both venom glands of D. palaestinae, and comparatively evaluating their contribution to the secreted venom concoction. Our findings highlight the disparity in the venom composition, function and toxicities of the two Daboia species. We also show that toxin production is not partitioned between the two venom glands of D. palaestinae.

Capillary leak syndrome due to Russell's viper envenomation-A doomy presage for treating clinician

Russell's viper envenomation is a major challenge to physicians providing intensive care due to diverse presentations and dismal outcomes. The venom can cause idiopathic systemic capillary leak syndrome manifesting with bilateral parotid swelling, hemoconcentration, and refractory shock. Physicians' awareness about this presentation is lacking. Delayed recognition of this syndrome leads to fatalities despite providing the best possible care. We hereby report a fatal case of Daboia russelii bite presenting as capillary leak syndrome. The aim is to create awareness among tropical physicians who are primary caregivers to these victims.

In Vitro Toxicity of Chinese Russell’s Viper (Daboia siamensis) Venom and Neutralisation by Antivenoms

Daboia siamensis (Russell’s viper) is a highly venomous and medically important snake in China, as well as much of Asia. There is minimal information on the pharmacological activity of the venom of the Chinese species, and currently no commercially available specific antivenom in China. This has led to the use of non-specific antivenoms to treat D. siamensis envenomation. In this study, the in vitro neurotoxicity and myotoxicity of D. siamensis venom was examined and the efficacy of four antivenoms was investigated, including the recently developed Chinese D. siamensis monovalent antivenom (C-DsMAV) and three commercially available antivenoms (Thai D. siamensis (Thai-DsMAV) monovalent antivenom, Deinagkistrodon acutus monovalent antivenom (DaAV), and Gloydius brevicaudus monovalent antivenom (GbAV). D. siamensis venom (10–30 µg/mL) caused the concentration-dependent inhibition of indirect twitches in the chick biventer cervicis nerve muscle preparation, without abolishing contractile responses to exogenous agonists ACh or CCh, indicating pre-synaptic neurotoxicity. Myotoxicity was also evident at these concentrations with inhibition of direct twitches, an increase in baseline tension, and the partial inhibition of ACh, CCh, and KCl responses. The prior addition of C-DsMAV or Thai-DsMAV prevented the neurotoxic and myotoxic activity of D. siamensis venom (10 µg/mL). The addition of non-specific antivenoms (GbAV and DaAV) partially prevented the neurotoxic activity of venom (10 µg/mL) but failed to neutralize the myotoxic effects. We have shown that D. siamensis venom exhibits in vitro weak presynaptic neurotoxicity and myotoxicity, which can be prevented by the pre-addition of the Chinese and Thai Russell’s viper antivenoms. Non-specific antivenoms were poorly efficacious. There should be further development of a monospecific antivenom against D. siamensis envenomation in China.

Evaluating Antivenom Efficacy against Echis carinatus Venoms—Screening for In Vitro Alternatives

In India, polyvalent antivenom is the mainstay treatment for snakebite envenoming. Due to batch-to-batch variation in antivenom production, manufacturers have to estimate its efficacy at each stage of IgG purification using the median effective dose which involves 100–120 mice for each batch. There is an urgent need to replace the excessive use of animals in snake antivenom production using in vitro alternatives. We tested the efficacy of a single batch of polyvalent antivenom from VINS bioproducts limited on Echis carinatus venom collected from three different locations—Tamil Nadu (ECVTN), Goa (ECVGO) and Rajasthan (ECVRAJ)—using different in vitro assays. Firstly, size-exclusion chromatography (SEC-HPLC) was used to quantify antivenom–venom complexes to assess the binding efficiency of the antivenom. Secondly, clotting, proteolytic and PLA2 activity assays were performed to quantify the ability of the antivenom to neutralize venom effects. The use of both binding and functional assays allowed us to measure the efficacy of the antivenom, as they represent multiple impacts of snake envenomation. The response from the assays was recorded for different antivenom–venom ratios and the dose–response curves were plotted. Based on the parameters that explained the curves, the efficacy scores (ES) of antivenom were computed. The binding assay revealed that ECVTN had more antivenom–venom complexes formed compared to the other venoms. The capacity of antivenom to neutralize proteolytic and PLA2 effects was lowest against ECVRAJ. The mean efficacy score of antivenom against ECVTN was the greatest, which was expected, as ECVTN is mainly used by antivenom manufacturers. These findings pave a way for the development of in vitro alternatives in antivenom efficacy assessment.

A comparative cross-reactivity and paraspecific neutralization study on Hypnale hypnale, Echis carinatus, and Daboia russelii monovalent and therapeutic polyvalent anti-venoms

Envenoming by the hump-nosed pit viper (Hypnale hypnale) raises concern as it inflicts significant debilitation and death in the Western Ghats of India and in the adjacent island nation of Sri Lanka. In India, its medical significance was realized only during 2007 due to its misidentification as Echis carinatus and sometimes as Daboia russelii. Of late, several case reports have underlined the ineptness of the existing polyvalent anti-venom therapy against H. hypnale envenoming. Currently, H. hypnale bite has remained dreadful in India due to the lack of neutralizing anti-venom therapy. Hence, this study was undertaken to establish a systematic comparative, biochemical, pathological, and immunological properties of Sri Lankan H. hypnale venom alongside Indian E. carinatus, and D. russelii venoms. All three venoms differed markedly in the extent of biochemical activities including proteolytic, deoxyribonuclease, L-amino acid oxidase, 5'-nucleotidase, hyaluronidase, and indirect hemolytic activities. The venoms also differed markedly in their pathological properties such as edema, hemorrhage, myotoxic, cardiotoxic, and coagulant activities. The venoms showed stark differences in their protein banding pattern. Strikingly, the affinity-purified rabbit monovalent anti-venoms prepared against H. hypnale, E. carinatus, and D. russelii venoms readily reacted and neutralized the biochemical and pathological properties of their respective venoms, but they insignificantly cross-reacted with, and thus failed to show paraspecific neutralization of any of the effects of the other two venoms, demonstrating the large degree of variations between these venoms. Further, the Indian therapeutic polyvalent anti-venoms from VINS Bioproducts, and Bharath Serums and Vaccines failed to protect H. hypnale venom-induced lethal effects in mice.

The Preclinical Evaluation of a Second-Generation Antivenom for Treating Snake Envenoming in India

Snake envenoming afflicts the Indian subcontinent with the highest rates of mortality (47,000) and morbidity globally. The only effective treatment for snakebites is the administration of antivenom, which is produced by the hyperimmunisation of equines. Commercial Indian antivenoms, however, have been shown to exhibit a poor preclinical performance in neutralising venom, as a result of inter- and intrapopulation snake venom variation. Additionally, their poor dose effectiveness necessitates the administration of larger volumes of antivenom for treatment, leading to several harmful side effects in snakebite victims, including serum sickness and fatal anaphylaxis. In this study, we employed chromatographic purification to enhance the dose efficacy of commercial Indian antivenoms. The efficacy of this ‘second-generation’ antivenom was comparatively evaluated against six other marketed antivenoms using a number of in vitro and in vivo preclinical assays, which revealed its superior venom recognition capability. Enhanced purity also resulted in significant improvements in dose effectiveness, as the ‘second-generation’ antivenom exhibited a 3 to 4.5 times increased venom neutralisation potential. Furthermore, preclinical assays revealed the increased effectiveness of the ‘second-generation’ antivenom in countering morbid effects inflicted by the ‘big four’ Indian snakes. Thus, we demonstrate the role of simpler purification steps in significantly enhancing the effectiveness of snakebite therapy in regions that are most affected by snakebites.

A paper microfluidic device based colorimetric sensor for the detection and discrimination of elapid versus viper envenomation

Snake bites are a neglected tropical disease, causing mortality and severe damage to various vital organs like the nervous system, kidneys and heart. There is increasing interest in designing new antivenom treatments that are more specific to particular groups (either taxonomic or regional) of species, given the increasing evidence that current polyvalent Indian antivenom is ineffective in many situations. Under these circumstances, being able to detect the species, or a group of species, responsible for the envenomation becomes important. Unfortunately, no such diagnostic tool is available in the Indian market. Such a tool will need to be rapid, sensitive and affordable. To address this need, we have combined the power of nanotechnology and paper microfluidics and herein report a device that has the ability to detect and differentiate viper venom from elapid and scorpion venom. In principle, this assay is based on the release of the dye from the stimuli-responsive glutaraldehyde cross-linked methylene blue-loaded gelatin (GMG) nanoparticles in the presence of snake venom metalloproteases and serine proteases. The developed equipment-free assay can detect and discriminate viper venom from that of elapids and scorpions. The low-end detection limit of the sensor is ∼3.0 ng for the saw-scaled viper Echis carinatus, while the same for Russell's viper Daboia russelii is ∼6.0 ng. The performance of the sensor remains unaltered for different batches of GMG nanoparticles. Altogether, this finding establishes the role of nanotechnology and paper microfluidics in the rapid and accurate detection of viper venom.

A simple mortality risk prediction score for viper envenoming in India (VENOMS): A model development and validation study

BACKGROUND

Snakebite is a neglected problem with a high mortality in India. There are no simple clinical prognostic tools which can predict mortality in viper envenomings. We aimed to develop and validate a mortality-risk prediction score for patients of viper envenoming from Southern India.

METHODS

We used clinical predictors from a prospective cohort of 248 patients with syndromic diagnosis of viper envenoming and had a positive 20-minute whole blood clotting test (WBCT 20) from a tertiary-care hospital in Puducherry, India. We applied multivariable logistic regression with backward elimination approach. External validation of this score was done among 140 patients from the same centre and its performance was assessed with concordance statistic and calibration plots.

FINDINGS

The final model termed VENOMS from the term "Viper ENvenOming Mortality Score included 7 admission clinical parameters (recorded in the first 48 hours after bite): presence of overt bleeding manifestations, presence of capillary leak syndrome, haemoglobin <10 g/dL, bite to antivenom administration time > 6.5 h, systolic blood pressure < 100 mm Hg, urine output <20 mL/h in 24 h and female gender. The lowest possible VENOMS score of 0 predicted an in-hospital mortality risk of 0.06% while highest score of 12 predicted a mortality of 99.1%. The model had a concordance statistic of 0·86 (95% CI 0·79-0·94) in the validation cohort. Calibration plots indicated good agreement of predicted and observed outcomes.

CONCLUSIONS

The VENOMS score is a good predictor of the mortality in viper envenoming in southern India where Russell's viper envenoming burden is high. The score may have potential applications in triaging patients and guiding management after further validation.

Taxon-selective venom variation in adult and neonate Daboia russelii (Russell's Viper), and antivenom efficacy

Major variations in venom composition can occur between juvenile and adult venomous snakes. However, due to logistical constraints, antivenoms are produced using adult venoms in immunising mixtures, possibly resulting in limited neutralisation of juvenile snake venoms. Daboia russelii is one of the leading causes of snakebite death across South Asia. Its venom is potently procoagulant, causing stroke in prey animals but causing in humans consumptive coagulopathy-a net anticoagulant state-and sometimes death resulting from hemorrhage. In this in vitro study, we compared the venom activity of-and antivenom efficacy against-six 2-week-old D. russelii relative to that of their parents. Using a coagulation analyser, we quantified the relative coagulotoxicity of these venoms in human, avian, and amphibian plasma. The overall potency on human plasma was similar across all adult and neonate venoms, and SII (Serum Institute of India) antivenom was equipotent in neutralising these coagulotoxic effects. In addition, all venoms were also similar in their action upon avian plasma. In contrast, the neonate venoms were more potent on amphibian plasma, suggesting amphibians make up a larger proportion of neonate diet than adult diet. A similar venom potency in human and avian plasmas but varying selectivity for amphibian plasma suggests ontogenetic differences in toxin isoforms within the factor X or factor V activating classes, thereby providing a testable hypothesis for future transcriptomics work. By providing insights into the functional venom differences between adult and neonate D. russelii venoms, we hope to inform clinical treatment of patients envenomated by this deadly species and to shed new light on the natural history of these extremely medically important snakes.

A Genus-Wide Bioactivity Analysis of Daboia (Viperinae: Viperidae) Viper Venoms Reveals Widespread Variation in Haemotoxic Properties

The snake genus Daboia (Viperidae: Viperinae; Oppel, 1811) contains five species: D. deserti, D. mauritanica, and D. palaestinae, found in Afro-Arabia, and the Russell's vipers D. russelii and D. siamensis, found in Asia. Russell's vipers are responsible for a major proportion of the medically important snakebites that occur in the regions they inhabit, and their venoms are notorious for their coagulopathic effects. While widely documented, the extent of venom variation within the Russell's vipers is poorly characterised, as is the venom activity of other species within the genus. In this study we investigated variation in the haemotoxic activity of Daboia using twelve venoms from all five species, including multiple variants of D. russelii, D. siamensis, and D. palaestinae. We tested the venoms on human plasma using thromboelastography, dose-response coagulometry analyses, and calibrated automated thrombography, and on human fibrinogen by thromboelastography and fibrinogen gels. We assessed activation of blood factors X and prothrombin by the venoms using fluorometry. Variation in venom activity was evident in all experiments. The Asian species D. russelii and D. siamensis and the African species D. mauritanica possessed procoagulant venom, while D. deserti and D. palaestinae were net-anticoagulant. Of the Russell's vipers, the venom of D. siamensis from Myanmar was most toxic and D. russelli of Sri Lanka the least. Activation of both factor X and prothrombin was evident by all venoms, though at differential levels. Fibrinogenolytic activity varied extensively throughout the genus and followed no phylogenetic trends. This venom variability underpins one of the many challenges facing treatment of Daboia snakebite envenoming. Comprehensive analyses of available antivenoms in neutralising these variable venom activities are therefore of utmost importance.

A Strategy for Efficient Preparation of Genus-Specific Diagnostic Antibodies for Snakebites

As said by former United Nations Secretary-General Kofi Annan, "Snakebite is the most important tropical disease you've never heard of." Listed as a priority neglected tropical disease by the World Health Organization, snakebite envenoming (SBE) kills in excess of 125,000 people per year. However, due to the complexity and overlap of snake venom compositions, few reliable venom diagnostic methods for genus-/species-specific identification, which is crucial for successful SBE therapy, are available. Here, we develop a strategy to select and prepare genus-specific snake venom antibodies, which allows rapid and efficient clinical diagnosis of snakebite. Multi-omics approaches are used to choose candidate antigens from snake venoms and identify genus-specific antigenic epitope peptide fragments (GSAEPs) with ideal immunogenicity, specificity, and spatial accessibility. Double-antibody sandwich ELISA kit was established by matching a polyclonal antibody against a natural antigen and a monoclonal antibody that was prepared by natural protein as antigen and can specifically target the GSAEPs. The kit shows the ability to accurately identify venoms from similar genera of Trimeresurus and Protobothrops with a detection limit of 6.25 ng/ml on the snake venoms and a little cross-reaction, thus proving high feasibility and applicability.

Venomics of the Enigmatic Andaman Cobra (Naja sagittifera) and the Preclinical Failure of Indian Antivenoms in Andaman and Nicobar Islands

The Andaman and Nicobar Islands are an abode to a diversity of flora and fauna, including the many endemic species of snakes, such as the elusive Andaman cobra (Naja sagittifera). However, the ecology and evolution of venomous snakes inhabiting these islands have remained entirely uninvestigated. This study aims to bridge this knowledge gap by investigating the evolutionary history of N. sagittifera and its venom proteomic, biochemical and toxicity profile. Phylogenetic reconstructions confirmed the close relationship between N. sagittifera and the Southeast Asian monocellate cobra (N. kaouthia). Overlooking this evolutionary history, a polyvalent antivenom manufactured using the venom of the spectacled cobra (N. naja) from mainland India is used for treating N. sagittifera envenomations. Comparative evaluation of venoms of these congeners revealed significant differences in their composition, functions and potencies. Given the close phylogenetic relatedness between N. sagittifera and N. kaouthia, we further assessed the cross-neutralising efficacy of Thai monovalent N. kaouthia antivenom against N. sagittifera venoms. Our findings revealed the inadequate preclinical performance of the Indian polyvalent and Thai monovalent antivenoms in neutralising N. sagittifera venoms. Moreover, the poor efficacy of the polyvalent antivenom against N. naja venom from southern India further revealed the critical need to manufacture region-specific Indian antivenoms.

Potential para-specific and geographical utility of Thai Green Pit Viper (Trimeresurus albolabris) Monovalent Antivenom: Neutralization of procoagulant and hemorrhagic activities of diverse Trimeresurus pit viper venoms

The Trimeresurus complex consists of diverse medically important venomous pit vipers that cause snakebite envenomation. Antivenoms, however, are in limited supply, and are specific to only two out of the many species across Asia. This study thus investigated the immunoreactivities of regional pit viper antivenoms toward selected Trimeresurus pit viper venoms, and examined the neutralization of their hemotoxic activities. Trimeresurus albolabris Monovalent Antivenom (TaMAV, Thailand) exhibited a higher immunoreactivity than Hemato Bivalent Antivenom (HBAV, raised against Trimeresurus stejnegeri and Protobothrops mucrosquamatus, Taiwan) and Gloydius brevicaudus Monovalent Antivenom (GbMAV, China), attributed to its monovalent nature and conserved antigens in the Trimeresurus pit viper venoms. The venoms showed moderate-to-strong in vitro procoagulant and in vivo hemorrhagic effects consistent with hemotoxic envenomation, except for the Sri Lankan Trimeresurus trigonocephalus venom which lacked hemorrhagic activity. TaMAV was able to differentially neutralize both in vitro and in vivo hemotoxic effects of the venoms, with the lowest efficacy shown against the procoagulant effect of T. trigonocephalus venom. The findings suggest that TaMAV is a potentially useful treatment for envenomation caused by hetero-specific Trimeresurus pit vipers, in particular those in Southeast Asia and East Asia. Clinical study is warranted to establish its spectrum of para-specific effectiveness, and dosages need be tailored to the different species in respective regions.

King or royal family? Testing for species boundaries in the King Cobra, Ophiophagus hannah (Cantor, 1836), using morphology and multilocus DNA analyses

In widespread species, the diverse ecological conditions in which the populations occur, and the presence of many potential geographical barriers through their range are expected to have created ample opportunities for the evolution of distinct, often cryptic lineages. In this work, we tested for species boundaries in one such widespread species, the king cobra, Ophiophagus hannah (Cantor, 1836), a largely tropical elapid snake distributed across the Oriental realm. Based on extensive geographical sampling across most of the range of the species, we initially tested for candidate species (CS) using Maximum-Likelihood analysis of mitochondrial genes. We then tested the resulting CS using both morphological data and sequences of three single-copy nuclear genes. We used snapclust to determine the optimal number of clusters in the nuclear dataset, and Bayesian Phylogenetics and Phylogeography (BPP) to test for likely species status. We used non-metric multidimensional scaling (nMDS) analysis for discerning morphological separation. We recovered four independently evolving, geographically separated lineages that we consider Confirmed Candidate Species: (1) Western Ghats lineage; (2) Indo-Chinese lineage (3) Indo-Malayan lineage; (4) Luzon Island lineage, in the Philippine Archipelago. We discuss patterns of lineage divergence, particularly in the context of low morphological divergence, and the conservation implications of recognizing several endemic king cobra lineages.

Addressing the global snakebite crisis with geo-spatial analyses - Recent advances and future direction

Venomous snakebite is a neglected tropical disease that annually leads to hundreds of thousands of deaths or long-term physical and mental ailments across the developing world. Insufficient data on spatial variation in snakebite risk, incidence, human vulnerability, and accessibility of medical treatment contribute substantially to ineffective on-ground management. There is an urgent need to collect data, fill knowledge gaps and address on-ground management problems. The use of novel, and transdisciplinary approaches that take advantage of recent advances in spatio-temporal models, 'big data', high performance computing, and fine-scale spatial information can add value to snakebite management by strategically improving our understanding and mitigation capacity of snakebite. We review the background and recent advances on the topic of snakebite related geospatial analyses and suggest avenues for priority research that will have practical on-ground applications for snakebite management and mitigation. These include streamlined, targeted data collection on snake distributions, snakebites, envenomings, venom composition, health infrastructure, and antivenom accessibility along with fine-scale models of spatio-temporal variation in snakebite risk and incidence, intraspecific venom variation, and environmental change modifying human exposure. These measures could improve and 'future-proof' antivenom production methods, antivenom distribution and stockpiling systems, and human-wildlife conflict management practices, while simultaneously feeding into research on venom evolution, snake taxonomy, ecology, biogeography, and conservation.

Prevention and improvement of clinical management of snakebite in Southern Asian countries: A proposed road map

In the Southern Asian countries, snakebite takes a substantial toll in terms of human life, inflicts acute morbidity and long term disability both physical and psychological, and therefore represents a neglected socio-economic problem and severe health issue that requires immediate medical attention. The 'Big Four' venomous snakes, viz. Daboia russelii, Naja naja, Bungarus caeruleus and Echis carinatus, are prominent, medically important species and are the most dangerous snakes of this region; therefore, the commercial polyvalent antivenom (PAV) contains antibodies against the venoms of these snakes. However, envenomations by species other than the 'Big Four' snakes are grossly neglected, and PAV is only partially effective in neutralizing the venom of these snakes. Many issues confounding effective treatment of snakebite are discussed in this review, and these hurdles preventing successful treatment of snakebite must be addressed. However, in South Asian countries, the pre-hospital treatment and appropriate first aid are equally important to mitigate the problem of snakebite and therefore, these issues are also highlighted here. Further, this review suggests a roadmap and guidelines for the prevention of snakebite and improvement of hospital management of snakebite in these Southern Asian countries.

Elucidating the Venom Diversity in Sri Lankan Spectacled Cobra (Naja naja) through De Novo Venom Gland Transcriptomics, Venom Proteomics and Toxicity Neutralization

Inadequate effectiveness of Indian antivenoms in treating envenomation caused by the Spectacled Cobra/Indian Cobra (Naja naja) in Sri Lanka has been attributed to geographical variations in the venom composition. This study investigated the de novo venom-gland transcriptomics and venom proteomics of the Sri Lankan N. naja (NN-SL) to elucidate its toxin gene diversity and venom variability. The neutralization efficacy of a commonly used Indian antivenom product in Sri Lanka was examined against the lethality induced by NN-SL venom in mice. The transcriptomic study revealed high expression of 22 toxin genes families in NN-SL, constituting 46.55% of total transcript abundance. Three-finger toxins (3FTX) were the most diversely and abundantly expressed (87.54% of toxin gene expression), consistent with the dominance of 3FTX in the venom proteome (72.19% of total venom proteins). The 3FTX were predominantly S-type cytotoxins/cardiotoxins (CTX) and α-neurotoxins of long-chain or short-chain subtypes (α-NTX). CTX and α-NTX are implicated in local tissue necrosis and fatal neuromuscular paralysis, respectively, in envenomation caused by NN-SL. Intra-species variations in the toxin gene sequences and expression levels were apparent between NN-SL and other geographical specimens of N. naja, suggesting potential antigenic diversity that impacts antivenom effectiveness. This was demonstrated by limited potency (0.74 mg venom/ml antivenom) of the Indian polyvalent antivenom (VPAV) in neutralizing the NN-SL venom. A pan-regional antivenom with improved efficacy to treat N. naja envenomation is needed.

Remarkable intrapopulation venom variability in the monocellate cobra (Naja kaouthia) unveils neglected aspects of India's snakebite problem

Interpopulation venom variation has been widely documented in snakes across large geographical distances. This variability is known to markedly influence the effectiveness of snakebite therapy, as antivenoms manufactured against one population may not be effective against others. In contrast, the extent of intrapopulation venom variability, especially at finer geographical scales, remains largely uninvestigated. Moreover, given the historical focus on the 'big four' Indian snakes, our understanding of venom variation in medically important yet neglected snakes, such as the monocellate cobra (Naja kaouthia), remains unclear. To address this shortcoming, we investigated N. kaouthia venoms sampled across a small spatial scale (<50 km) in Eastern India. An interdisciplinary approach employed in this study unveiled considerable intrapopulation differences in the venom proteomic composition, pharmacological and biochemical activities, and toxicity profiles. Documentation of stark differences in venoms at such a finer geographical scale, despite the influence of similar ecological and environmental conditions, is intriguing. Furthermore, evaluation of in vitro and in vivo venom recognition and neutralisation potential of Indian polyvalent 'big four' antivenoms and Thai monovalent N. kaouthia antivenom revealed concerning deficiencies. These results highlight the negative impact of phylogenetic divergence and intrapopulation snake venom variation on the effectiveness of conventional antivenom therapy. SIGNIFICANCE: In contrast to our understanding of snake venom variation across large distances, which is theorised to be shaped by disparities in ecology and environment, intrapopulation variation at finer geographic scales remains scarcely investigated. Assessment of intrapopulation venom variability in Naja kaouthia at a small spatial scale (<50 km) in Eastern India unravelled considerable differences in venom compositions, activities and potencies. While the influence of subtle differences in prey preference and local adaptations cannot be ruled out, these findings, perhaps, also emphasise the role of accelerated molecular evolutionary regimes that rapidly introduce variations in evolutionarily younger lineages, such as advanced snakes. The inability of 'big four' Indian antivenoms and Thai N. kaouthia monovalent antivenom in countering these variations highlights the importance of phylogenetic considerations for the development of efficacious snakebite therapy. Thus, we provide valuable insights into the venoms of one of the most medically important yet neglected Indian snakes.