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

Kraits of Indian subcontinent: Natural history, risks, venom variation, lethality and treatment strategies - A comprehensive review

The World Health Organization (WHO) has re-classified "Snakebite" as a Neglected Tropical Disease in 2017, and estimated that as many as 5.4 million people suffer from snakebites every year. Out of this large number of snakebites, envenoming occurs in about 50 % of the cases, and the number of resulting deaths could be as high as 138,000. The genus Bungarus commonly known as kraits are medically important elapid snakes widely distributed in the Indian subcontinent, southern China and the Southeast Asian countries (except Philippines). The Indian subcontinent (India, Bangladesh, Bhutan, Nepal, Pakistan, Sri Lanka and Maldives) is home to 8-9 krait species, among which B. caeruleus and B. niger are highly venomous. This review presents the current state of knowledge on krait bites in the Indian subcontinent. The risk of envenomation by kraits, the venom lethality and krait bite management in the Indian subcontinent have been critically analyzed. Moreover, the issue of dry bites from kraits and their management has also been reviewed. Furthermore, critical aspects, such as knowledge of snakebite management among healthcare workers, clinical symptoms of snakebite patients, and treatment in healthcare facilities including antivenom administration and their clinical efficacy, have helped us in identifying the critical knowledge gaps. Proposed preventive measures will help to reduce krait bite associated mortality and morbidity. Moreover, development and accessibility to affordable treatment options may help in the effective management of krait bites.

Snakebite envenoming in India: it is time we look beyond the concept of the Big Four species

India faces substantial challenges from snakebite envenoming secondary to the high morbidity, mortality and financial burden, particularly in rural communities. While concentrated on the 'Big Four' venomous species, recent research indicates a necessity to expand the focus to encompass additional medically relevant species. This review emphasizes the geographic heterogeneity in venom among these snakes, which impacts antivenom effectiveness and necessitating region-specific formulations. This analysis highlights the shortcomings of current antivenoms and identifies non-Big Four species involved in snakebite envenoming, advocating for an urgent shift to inclusive antivenom strategies that integrate local venom profiles to enhance treatment effectiveness and thereby reduce snakebite-related morbidity and mortality. Improved training for healthcare providers and enhancements in anti-snake venom quality are essential for meeting the World Health Organization's 2030 Sustainable Development Goal objective of halving snakebite-related fatalities and disabilities. Incorporating snakebite management into national health programs and conducting epidemiological research systematically are crucial to mitigating this preventable health concern.

Diagnosis of Indian Big Four and monocled Cobra snakebites in envenomed plasma using smartphone-based digital imaging colourimetry method

BACKGROUND

Venomous or dry bites can result from snake envenomation. Therefore, developing a detection test for venomous snakebites in envenomed patients can prevent from unnecessary antivenom therapy for dry bites, thereby, saving them from adverse effects and cost of antivenom therapy.

METHODOLOGY

This study demonstrates a method for the diagnosis of medically significant 'Big Four' Indian snake venoms (Naja naja, Bungarus caeruleus, Daboia russelii, Echis carinatus) in the plasma of experimentally envenomed animals (envenomed under laboratory conditions). Rabbit polyclonal antibodies (PAbs) were produced by generating modified bespoke peptides identified by computational analysis from the antigenic sites of the main toxins found in the proteome of India's 'Big Four' venomous snakes. The polyclonal antibody formulation (FPAb) prepared by mixing the five representative PAbs in the ratio of 1:1:1:1:1 demonstrated synergistic immune recognition of the 'Big Four' snakes and Naja kaouthia venoms. The recognition for these venoms under in vitro and in vivo conditions by FPAb was significantly higher (p<0.05) than commercial polyvalent antivenom produced against native venom toxins. The FPAb was tested to detect the venoms in subcutaneously envenomed rat plasmas until 240 minutes post-injection. Fourier-transform infrared spectroscopy, zeta potential, transmission electron microscopy, and atomic force microscopy characterised gold nanoparticles (AuNP) conjugated with FPAb. The FPAb-conjugated AuNP demonstrated aggregation upon interaction with venom toxins, changing the colour from red through burgundy to blue, monitored using a smartphone. From the digital image colourimetry analysis of the images, calibration curves for venoms were obtained, and each venom in the envenomed plasma at different time intervals was quantified using these curves.

CONCLUSION

A method for detection of venomous snakebites has been reported. The formulation of polyclonal antibodies generated against toxins of 'Big Four' venomous snakes of India immune-recognise venoms of 'Big Four' venomous snakes of India and N. kaouthia venoms under both in vitro and in vivo conditions. The antibody formulation conjugated to AuNP detected the venoms in envenomed plasma. This method of detection has potential to be useful for snakebite management in clinical settings.

Challenges in Snakebite Management in India: Insights from a Physician Survey with Special Focus on Kerala and treatment of bites by Hump-nosed Pit Vipers (Hypnale spp.)

BACKGROUND

India has a high incidence of snakebite-related mortality, making effective snakebite management crucial. This study aimed to explore current practices, challenges, and opportunities for improvement in snakebite management across India.

METHODS

A cross-sectional survey was conducted among physicians in India covering aspects such as scope of practice, snake identification, first aid measures, institutional management, and specific management practices for hump-nosed pit viper (Hypnale hypnale) bites. The survey included 37 questions across 5 sections, with data collected via emails, professional networks, and online platforms. Statistical analysis was performed using SPSS Statistics 23 (IBM Corp, Armonk, NY), and manual thematic analysis was applied to open-ended responses.

RESULTS

The survey revealed a discrepancy between physicians' confidence and accuracy in snake identification, with some still reporting outdated first aid and treatment practices. Despite recognizing the importance of snake species identification, a significant portion of respondents incorrectly identified the snakes. The study highlighted variability in institutional practices for snakebite management, such as administering prophylactic antibiotics and tetanus prophylaxis and monitoring periods for asymptomatic patients. In managing H hypnale viper bites, a demand for specific guidelines and a monovalent antivenom was evident because the current polyvalent antivenom is ineffective for this species.

CONCLUSIONS

The survey emphasizes the need for improved training in snake identification, standardized treatment protocols, and the development of region-specific antivenoms. It emphasizes the necessity of updating guidelines to address the unique challenges of snakebite management in India, particularly for species not covered by existing antivenoms.

Epidemiological models to estimate the burden of snakebite envenoming: A systematic review

BACKGROUND

Epidemiological modelling studies in snakebite envenoming research are evolving. Their techniques can be essential in filling the knowledge gap needed to attain the World Health Organization's (WHO) goal of halving the burden of snakebite envenoming by complementing the current data scarcity. Hence, there is a need for a systematic review to summarise epidemiological models used in estimating the burden of snakebite envenoming.

METHODS

We conducted a systematic review by searching PubMed, EMBASE, and Scopus to identify articles reporting epidemiological models in snakebite envenoming from database inception to 31st December 2023. A narrative synthesis was performed to summarise types of models, methodologies, input parameters, model outputs, and associating factors.

RESULTS

Thirty-nine modelling studies were included from 2426 retrieved articles, comprising statistical models (76.9%) and mathematical models (23.1%). Most of the studies were conducted in South Asia, (35.9%) and Latin America (35.9%), and only a few (5.1%) were a global burden estimation. The eligible studies constructed 42 epidemiological models, of which 33 were statistical models that included regression, (60.6%) geostatistical (21.2%), and time series, (18.2%) while 9 mathematical models comprised compartmental, (44.4%) agent-based, (22.2%) transmission dynamics, (11.1%) network, (11.1%) and a simple mathematical model (11.1%). The outputs of the models varied across the study objectives. Statistical models analysed the relationship between incidence, (83.3%) mortality, (33.3%) morbidity (16.7%) and prevalence (10.0%) and their associating factors (environmental, [80%] socio-demographic [33.3%] and therapeutic [10.0%]). Mathematical models estimated incidence, (100%) mortality (33.3%), and morbidity (22.2%). Five mathematical modelling studies considered associating factors, including environmental (60%) and socio-demographic factors (40%).

CONCLUSION

Mathematical and statistical models are crucial for estimating the burden of snakebite envenoming, offering insights into risk prediction and resource allocation. Current challenges include low-quality data and methodological heterogeneity. Modelling studies are needed, and their continued improvement is vital for meeting WHO goals. Future research should emphasise standardised methodologies, high-quality community data, and stakeholder engagement to create accurate, applicable models for prevention and resource optimization in high-burden regions, including Africa and Asia.

Antivenom ineffectiveness in Echis carinatus sochureki envenoming: a five-year, single-centre experience from India

BACKGROUND

Snakebite is a neglected tropical disease that causes significant morbidity and mortality in India. In this study, we describe the clinical characteristics and outcomes of Echis carinatus sochureki envenoming from Western Rajasthan. We document the clinical ineffectiveness of the currently available Indian polyvalent antivenom in managing E. c. sochureki envenoming.

METHODS

In this ambispective study, conducted from 14 April 2019 to 15 April 2024, we enrolled all patients presenting to our emergency department at a tertiary care centre in Jodhpur, Rajasthan, with a history of snakebite. After they provided informed consent, the demographic details, bite geo-location, bite-to-antivenom time, antivenom dose, coagulation profile, mortality and duration of hospital stay of those patients with E. c. sochureki envenoming were recorded.

RESULTS

Of 210 patients screened, 105 had E. c. sochureki envenoming, 103 venom-induced consumption coagulopathy, 36 (34.3%) local bleeding and 55 (52.3%) systemic bleeding. The median bite-to-antivenom time was 2 (IQR: 1.13-4.0) h. The median antivenom dose was 22 (IQR: 10-30) vials. Of 92 patients who received antivenom, 63 (68.4%) were unresponsive. Total antivenom dose and geographical location (West zone) were significant predictors of antivenom unresponsiveness. Fifty-three of 70 patients (75.7%) had delayed hypofibrinogenaemia. The mean hospital stay was 8.3±7.1 d with nine (8.6%) mortalities.

CONCLUSIONS

Our study highlights the alarming finding of poor antivenom response to E. c. sochureki envenoming, with significant clinical bleeding and delayed coagulopathy. There is an urgent need for region-specific antivenom in Western India.

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.

Protobothrops jerdonii (Jerdon's pit viper) and Protobothrops himalayanus (Himalayan lance-headed pit viper) bites: Clinical report on envenomings from North-East India, managed through remote consultation by a national-level Poison control center

Members of the genus Protobothrops are amongst the more than twenty-eight range-restricted Indian pit viper species. Their bites and envenomings are rarely documented from India. Pit viper envenomings can be challenging to treat in the Indian setting, since available antivenoms do not satisfactorily neutralize their venoms. Herein, we present the first Indian reports on bites and envenoming by Protobothrops jerdonii and Protobothrops himalayanus resulting in local effects, coagulopathy and acute kidney injury in the case of the former and possible mild, isolated coagulopathy in the case of the latter; and discuss management-related challenges in the context of absent specific antivenoms.

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.

Isolation and Functional Characterization of Erythrofibrase: An Alfa-Fibrinogenase Enzyme from Trimeresurus erythrurus Venom of North-East India

Green pit viper bites induce mild toxicity with painful local swelling, blistering, cellulitis, necrosis, ecchymosis and consumptive coagulopathy. Several bite cases of green pit vipers have been reported in several south-east Asian countries including the north-eastern region of India. The present study describes isolation and characterization of a haemostatically active protein from Trimeresurus erythrurus venom responsible for coagulopathy. Using a two-step chromatographic method, a snake venom serine protease erythrofibrase was purified to homogeneity. SDS-PAGE of erythrofibrase showed a single band of ~30 kDa in both reducing and non-reducing conditions. The primary structure of erythrofibrase was determined by ESI LC-MS/MS, and the partial sequence obtained showed 77% sequence similarity with other snake venom thrombin-like enzymes (SVTLEs). The partial sequence obtained had the typical 12 conserved cysteine residues, as well as the active site residues (His57, Asp102 and Ser195). Functionally, erythrofibrase showed direct fibrinogenolytic activity by degrading the Aα chain of bovine fibrinogen at a slow rate, which might be responsible for causing hypofibrinogenemia and incoagulable blood for several days in envenomated patients. Moreover, the inability of Indian polyvalent antivenom (manufactured by Premium Serum Pvt. Ltd., Maharashtra, India) to neutralize the thrombin-like and plasmin-like activity of erythrofibrase can be correlated with the clinical inefficacy of antivenom therapy. This is the first study reporting an α-fibrinogenase enzyme erythrofibrase from T. erythrurus venom, which is crucial for the pathophysiological manifestations observed in envenomated victims.

Identification of poorly immunodepleted phospholipase A2 (PLA2) proteins of Bungarus fasciatus venom from Assam, India and evaluation of Indian polyvalent antivenom using third-generation antivenomics

Bungarus fasciatus also referred to as the Banded krait is a snake which possesses venom and belongs to the Elapidae family. It is widely distributed across the Indian subcontinent and South East Asian countries and is responsible for numerous snakebites in the population. B. fasciatus possesses a neurotoxic venom and envenomation by the snake results in significant morbidity and occasional morbidity in the victim if not treated appropriately. In this study, the efficacy of Indian polyvalent antivenom (Premium Serums polyvalent antivenom) was evaluated against the venom of B. fasciatus from Guwahati, Assam (India) employing the Third-generation antivenomics technique followed by identification of venom proteins from three poorly immunodepleted peaks (P5, P6 and P7) using LC-MS/MS analysis. Seven proteins were identified from the three peaks and all these venom proteins belonged to the phospholipase A2 (PLA2) superfamily. The identified PLA2 proteins were corroborated by the in vitro enzymatic activities (PLA2 and Anticoagulant activity) exhibited by the three peaks and previous reports of pathological manifestation in the envenomated victims. Neutralization of enzymatic activities by Premium Serums polyvalent antivenom was also assessed in vitro for crude venom, P5, P6 and P7 which revealed moderate to poor inhibition. Inclusion of venom proteins/peptides, which are non-immunodepleted or poorly immunodepleted, into the immunization mixture of venom used for antivenom production may help in enhancing the efficacy of the polyvalent antivenom.