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

Composition, pharmacology, and pathophysiology of the venom of monocled cobra (Naja kaouthia)- a medically crucial venomous snake of southeast Asia: An updated review

The Monocled Cobra (Naja kaouthia), a category one medically significant snake from the Elapidae family, inflicts severe envenomation in South and Southeast Asian countries. N. kaouthia is distributed throughout the eastern and northeastern parts of India, Nepal, Bangladesh, Myanmar, Thailand, Vietnam, Malaysia, and southwestern China. Envenomation by N. kaouthia is a medical emergency, and the primary clinical symptoms are neurotoxicity and localized tissue destruction. Unfortunately, data on the actual magnitude of N. kaouthia envenomation is scarce due to poor record keeping, lack of diagnostic kits, and region-wise well-coordinated epidemiological surveys. The present review highlights the diversity in the composition of N. Kaouthia venom (NKV) across various geographical regions, as revealed through biochemical and proteomic analyses. The qualitative and quantitative differences in the toxin isoforms result in differences in lethality and pathophysiological manifestation that may limit the effectiveness of antivenom therapy. Studies on commercial polyvalent antivenom (PAV) effectiveness against distinct NKV samples have revealed varying toxicity and enzymatic activity neutralization. Additionally, the identification of snake venom's poorly immunogenic toxins by mass spectrometry, quantification of venom-specific antibodies, and implications for antivenom therapy against snakebites are highlighted. Future directions involve clinical studies on NK envenomation where the snake is frequently encountered and the correlation of this data with NKV composition in that region. For more efficient and superior hospital management of NK envenomation, research should enhance the current immunization procedure to boost the development of antibodies against less immunogenic venom components of this snake.

Snakebite Management: The Need of Reassessment, International Relations, and Effective Economic Measures to Reduce the Considerable SBE Burden

The sole treatment for snakebite envenomation (SBE), the anti-snake venom (ASV), suffers from considerable drawbacks, including side effects and limited species specificity. Additionally, despite its existence for more than a century, uniform availability of good quality ASV does not yet exist. The present review describes the journey of a SBE victim and highlights the global crisis of SBE management. A detailed analysis of the current ASV market has also been presented along with the worldwide snake distribution. The current production of country specific licensed ASV throughout the globe along with their manufacturers has been examined at the snake species level. Furthermore, a detailed analysis of on-ground situation of SBE management in antivenom manufacturing countries has been done using the most recent literature. Additionally, the export and import of different ASVs have been discussed in terms of procurement policies of individual countries, their shortcomings, along with the possible solution at the species level. It is interesting to note that in most countries, the existence of ASV is really either neglected or overstated, implying that it is there but unsuitable for use, or that it is not present but can be obtained from other countries. This highlights the urgent need of significant reassessment and international collaborations not just for development and production, but also for procurement, distribution, availability, and awareness. A PROMISE (Practical ROutes for Managing Indigenous Snakebite Envenoming) approach has also been introduced, offering simple, economical, and easy to adopt steps to efficiently alleviate the worldwide SBE burden.

Evaluation of Neutralization Potential of Naja naja and Daboiarusselii Snake Venom by Root Extract of Cyanthillium cinereum

Aim

One of the main reasons for the death due to snake bites is the non-availability of antivenoms in the regions where they are needed. The use of medicinal plants and plant-based natural products as an alternative to antivenom will become a milestone in snake bite envenomation. The present study investigates the in vitro antivenom properties of Cyanthillium cinereum root extracts.

Materials and methods

The C. cinereum root's aqueous extract was prepared by the Soxhlet extraction method, and phytochemical screening was performed to detect the presence of various bioactive compounds. Thin-layer chromatography (TLC) and gas chromatography-mass spectrometry (GC-MS) analysis were performed for the detection and identification of phytochemical constituents. In this study, an in vitro model is used to assess the antivenom capability of aqueous extract. Venom toxicity and neutralization assays were as follows: An in vitro pharmacological evaluation was performed by direct hemolysis assay, indirect hemolytic assay, proteolytic activity, neutralization of procoagulant activity, and gelatin liquefaction method.

Results

Qualitative analysis of phytochemicals by the standard method showed the presence of various phytochemical constituents. Also, GC-MS analysis showed the presence of three major compounds that possess antivenom activity from the obtained 60 bioactive compounds, and their chemical structures were also determined. Venom protein profiling was performed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis. The plant extract was able to neutralize the Naja naja (N. naja) and Daboia russelii (D. russelii) venom induced hemolysis and it was reduced below 50 and 40%, respectively and the extract was also able to reduce the hemolytic halo produced by venoms. Procoagulant activity and gelatin liquefaction assay showed that venom-induced clotting was neutralized by increasing the root extract concentration sufficiently.

Conclusion

The aqueous extract of the root of C. cinereum showed potent in vitro venom-neutralizing activity, and it can be used as a formidable therapeutic agent against N. naja and D. russelii envenomation.

How to cite this article

Suji S, Dinesh MD, Keerthi KU, Anagha KP, Arya J, Anju KV. Evaluation of Neutralization Potential of Naja naja and Daboia russelii Snake Venom by Root Extract of Cyanthillium cinereum. Indian J Crit Care Med 2023;27(11):821-829.

A Novel Therapeutic Formulation for the Improved Treatment of Indian Red Scorpion (Mesobuthus tamulus) Venom-Induced Toxicity-Tested in Caenorhabditis elegans and Rodent Models

Indian Red Scorpion (Mesobuthus tamulus) stings are a neglected public health problem in tropical and sub-tropical countries, including India. The drawbacks of conventional therapies using commercial anti-scorpion antivenom (ASA) and α1-adrenoreceptor antagonists (AAA) have prompted us to search for an adequate formulation to improve treatment against M. tamulus stings. Novel therapeutic drug formulations (TDF) of low doses of commercial ASA, AAA, and ascorbic acid have remarkably improved in neutralising the in vivo toxic effects of M. tamulus venom (MTV) tested in Caenorhabditis elegans and Wistar strain albino rats in vivo models. The neutralisation of MTV-induced production of free radicals, alteration of the mitochondrial transmembrane potential, and upregulated expression of genes involved in apoptosis, detoxification, and stress response in C. elegans by TDF surpassed the same effect shown by individual components of the TDF. Further, TDF efficiently neutralized the MTV-induced increase in blood glucose level within 30 to 60 min post-treatment, organ tissue damage, necrosis, and pulmonary oedema in Wistar rats, indicating its clinical application for effecting treating M. tamulus envenomation. This study demonstrates for the first time that C. elegans can be a model organism for screening the neutralization potency of the drug molecules against a neurotoxic scorpion venom.

A retrospective analysis of epidemiology, clinical features of envenomation, and in-patient management of snakebites in a model secondary hospital of Assam, North-east India

Assam, a Northeastern State of India, is inhabited by several venomous snake species causing substantial morbidity and mortality. The data on the epidemiology of snakebites and their management is underreported in this region. Hence, a secondary health-based retrospective study was carried out at Demow Model Hospital, Sivasagar, Assam, to evaluate the clinical and epidemiological profile of snakebite cases reported in this rural hospital and their management. Snakebites occurring between April 2018 to August 2022 were reviewed based on socio-demographic details of the patient, clinical symptoms, and treatment using a standard questionnaire. Out of the 1011 registered snakebite cases, 139 patients (13.7%) counted for venomous bites, among which 92 patients (66.19%) accounted for viper bites (green pit viper and Salazar's pit viper), and 30 patients (21.5%) were bitten by elapid snakes (Indian monocled Cobra, banded krait, and greater/lesser black krait). A maximum number of snakebite cases (80.5%) were reported from the interior rural villages and documented from July to September (51.3%). Elapid snake envenomed patients, except one, were successfully treated with commercial antivenom, neostigmine, and glycopyrrolate. Because commercial polyvalent antivenom against "Big Four" venomous snakes of India showed poor neutralization of pit-vipers envenomation; therefore, pit-viper bite patients were treated with repurposed drugs magnesium sulfate and glycerin compression dressing. Adverse serum reactions were reported only in 3 (11.1%) cases. The preventive measures and facilities adopted at the Demow Model Hospital significantly reduce snakebite death and morbidity; therefore, they can be s practised across various states in India as a prototype.

Catalytically Active Snake Venom PLA2 Enzymes: An Overview of Its Elusive Mechanisms of Reaction

Snake venom-secreted phospholipase A₂ (svPLA₂) enzymes, both catalytically active and inactive, are a central component in envenoming. These are responsible for disrupting the cell membrane's integrity, inducing a wide range of pharmacological effects, such as the necrosis of the bitten limb, cardiorespiratory arrest, edema, and anticoagulation. Although extensively characterized, the reaction mechanisms of enzymatic svPLA₂ are still to be thoroughly understood. This review presents and analyses the most plausible reaction mechanisms for svPLA_2, such as the "single-water mechanism" or the "assisted-water mechanism" initially proposed for the homologous human PLA₂. All of the mechanistic possibilities are characterized by a highly conserved Asp/His/water triad and a Ca²⁺ cofactor. The extraordinary increase in activity induced by binding to a lipid-water interface, known as "interfacial activation," critical for the PLA₂s activity, is also discussed. Finally, a potential catalytic mechanism for the postulated noncatalytic PLA₂-like proteins is anticipated.

Perspectives on snakebite envenoming care needs across different sociocultural contexts and health systems: A comparative qualitative analysis among US and Brazilian health providers

With the advancements in therapeutics and available treatment options, almost all deaths and permanent disabilities from snakebite envenoming (SBE) are preventable. The challenge lies in implementing these evidence-based treatments and practices across different settings and populations. This study aims to compare data on provider perceptions of SBE care across health systems and cultural contexts to inform potential implementation science approaches. We hypothesize different health systems and cultural contexts will influence specific perceived needs to provide adequate snakebite care within central tenets of care delivery (e.g., cost, access, human resources). We previously conducted exploratory descriptive studies in the US and Brazil in order to understand the experience, knowledge, and perceptions of health professionals treating SBE. In the US, in-depth interviews were performed with emergency physicians from January 2020 to March 2020. In BR, focus group discussions were conducted with health professionals from community health centers at the end of June 2021. The focus group discussions (BR) were originally analyzed through an inductive thematic analysis approach. We conducted a secondary qualitative analysis in which this codebook was then applied to the interviews (US) in a deductive content analysis. The analysis concluded in August 2022. Brazil participants were physicians (n=5) or nurses (n=20) from three municipalities in the State of Amazonas with an average of three years of professional experience. US participants were emergency physicians (n=16) with an average of 15 years of professional experience. Four main themes emerged: 1) barriers to adequate care on the patient and/or community side and 2) on the health system side, 3) perceived considerations for how to address SBE, and 4) identified needs for improving care. There were 25 subthemes within the four themes. These subthemes were largely the same across the Brazil and US data, but the rationale and content within each shared subtheme varied significantly. For example, the subtheme "role of health professionals in improving care" extended across Brazil and the US. Brazil emphasized the need for task-shifting and -sharing amongst health care disciplines, whereas the US suggested specialized approaches geared toward increasing access to toxicologists and other referral resources. Despite similar core barriers to adequate snakebite envenoming care and factors to consider when trying to improve care delivery, health professionals in different health systems and sociocultural contexts identified different needs. Accounting for, and understanding, these differences is crucial to the success of initiatives intended to strengthen snakebite envenoming care. Implementation science efforts, with explicit health professional input, should be applied to develop new and/or adapt existing evidence-based treatments and practices for SBE.

Effect of Several Naja atra Antivenom Injection Methods on the Rabbit Model of Naja naja atra Bite Poisoning

Snakebite is a global public health concern, which often occurs in tropical and subtropical underdeveloped areas, but it is often neglected. In the southern China, Naja naja atra (Chinese cobra) is a common venomous snake that causes swelling and necrosis of local tissues, even amputation and death. Currently, the main therapy is the administration of Naja atra antivenom, which greatly reduces mortality. However, the antivenom is not particularly effective in the improvement of local tissue necrosis. Clinically, antivenom is mainly administered intravenously. We speculated that the method of injection influences the efficacy of antivenom. In this study, the rabbit model was used to explore the effects of different antivenom injection methods on systemic and local poisoning symptoms. If topical injection of antivenom contributes to ameliorate tissue necrosis, then we need to reconsider the use of Naja atra antivenom.

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.

Pharmacological re-assessment of traditional medicinal plants-derived inhibitors as antidotes against snakebite envenoming: A critical review

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional healers have used medicinal plants to treat snakebite envenomation worldwide; however, mostly without scientific validation. There have been many studies on the therapeutic potential of the natural products against snake envenomation.

AIM OF THE STUDY

This review has highlighted snake venom inhibitory activity of bioactive compounds and peptides from plants that have found a traditional use in treating snakebite envenomation. We have systematically reviewed the scenario of different phases of natural snake venom inhibitors characterization covering a period from 1994 until the present and critically analysed the lacuna of the studies if any, and further scope for their translation from bench to bedside.

MATERIALS AND METHODS

The medicinal plant-derived compounds used against snakebite therapy were reviewed from the available literature in public databases (Scopus, MEDLINE) from 1994 till 2020. The search words used were 'natural inhibitors against snakebite,' 'natural products as therapeutics against snakebite,' 'natural products as antidote against snake envenomation,' ' snake venom toxin natural inhibitors,' 'snake venom herbal inhibitors'. However, the scope of this review does not include computational (in silico) predictions without any wet laboratory validation and snake venom inhibitory activity of the crude plant extracts. In addition, we have also predicted the ADMET properties of the identified snake venom inhibitors to highlight their valuable pharmacokinetics for future clinical studies.

RESULTS

The therapeutic application of plant-derived natural inhibitors to treat snakebite envenomation as an auxiliary to antivenom therapy has been gaining significant momentum. Pharmacological reassessment of the natural compounds derived from traditional medicinal plants has demonstrated inhibition of the principal toxic enzymes of snake venoms at various extents to curb the lethal and/or deleterious effects of venomous snakebite. Nevertheless, such molecules are yet to be commercialized for clinical application in the treatment of snakebite. There are many obstacles in the marketability of the plant-derived natural products as snake envenomation antidote and strategies must be explored for the translation of these compounds from drug candidates to their clinical application.

CONCLUSION

In order to minimize the adverse implications of snake envenomation, strategies must be developed for the smooth transition of these plant-derived small molecule inhibitors from bench to bedside. In this article we have presented an inclusive review and have critically analysed natural products for their therapeutic potential against snake envenomation, and have proposed a road map for use of natural products as antidote against snakebite.

Venom production and secretion in reptiles

The venom glands of reptiles, particularly those of front-fanged advanced snakes, must satisfy conflicting biological demands: rapid synthesis of potentially labile and highly toxic proteins, storage in the gland lumen for long periods, stabilization of the stored secretions, immediate activation of toxins upon deployment and protection of the animal from the toxic effects of its own venom. This dynamic system could serve as a model for the study of a variety of different phenomena involving exocrine gland activation, protein synthesis, stabilization of protein products and secretory mechanisms. However, these studies have been hampered by a lack of a long-term model that can be propagated in the lab (as opposed to whole-animal studies). Numerous attempts have been made to extend the lifetime of venom gland secretory cells, but only recently has an organoid model been shown to have the requisite qualities of recapitulation of the native system, self-propagation and long-term viability (>1 year). A tractable model is now available for myriad cell- and molecular-level studies of venom glands, protein synthesis and secretion. However, venom glands of reptiles are not identical, and many differ very extensively in overall architecture, microanatomy and protein products produced. This Review summarizes the similarities among and differences between venom glands of helodermatid lizards and of rear-fanged and front-fanged snakes, highlighting those areas that are well understood and identifying areas where future studies can fill in significant gaps in knowledge of these ancient, yet fascinating systems.