Vulnerability to snakebite envenoming: a global mapping of hotspots

Assessing the practicalities of joint snakebite and dog rabies control programs: Commonalities and potential pitfalls

Both rabies and snakebite primarily affect underserved and impoverished communities globally, with an estimated 200,000 people dying from these diseases annually, and the greatest burden being in Africa and Asia. Both diseases have been neglected and have thus been denied appropriate prioritization, support, and interventions, and face many of the challenges common to all neglected tropical diseases (NTDs). In line with the call for integrated approaches between NTDs in the recent NTD Roadmap, we sought to build upon previous conceptualizations for an integrated approach by identifying the commonalities between snakebite and rabies to explore the feasibility of an integrated approach. While multiple areas for potential integration are identified, we highlight the potential pitfalls to integrating rabies and snakebite programs, considering the nuances that make each disease and its intervention program unique. We conclude that health system strengthening, and capacity building should be the focus of any integrated approach among NTDs, and that by strengthening overall health systems, both rabies and snakebite can advocate for further support from governments and stakeholders.

Access to antivenoms in the developing world: A multidisciplinary analysis

Access to safe, effective, quality-assured antivenom products that are tailored to endemic venomous snake species is a crucial component of recent coordinated efforts to reduce the global burden of snakebite envenoming. Multiple access barriers may affect the journey of antivenoms from manufacturers to the bedsides of patients. Our review describes the antivenom ecosystem at different levels and identifies solutions to overcome these challenges. At the global level, there is insufficient manufacturing output to meet clinical needs, notably for antivenoms intended for use in regions with a scarcity of producers. At national level, variable funding and deficient regulation of certain antivenom markets can lead to the procurement of substandard antivenom. This is particularly true when producers fail to seek registration of their products in the countries where they should be used, or where weak assessment frameworks allow registration without local clinical evaluation. Out-of-pocket expenses by snakebite victims are often the main source of financing antivenoms, which results in the underuse or under-dosing of antivenoms, and a preference for low-cost products regardless of efficacy. In resource-constrained rural areas, where the majority of victims are bitten, supply of antivenom in peripheral health facilities is often unreliable. Misconceptions about treatment of snakebite envenoming are common, further reducing demand for antivenom and exacerbating delays in reaching facilities equipped for antivenom use. Multifaceted interventions are needed to improve antivenom access in resource-limited settings. Particular attention should be paid to the comprehensive list of actions proposed within the WHO Strategy for Prevention and Control of Snakebite Envenoming.

Snakebite frequencies and envenomation case management in primary health centers of the Bobo-Dioulasso health district (Burkina Faso) from 2014 to 2018

Background

Snakebite envenomation is a significant public health problem in Burkina Faso. Our study describes the epidemiological and therapeutic aspects of snakebite cases at primary health centers in Houet Province, which is located in the western area of Burkina Faso.

Methods

We conducted a retrospective study of 664 snakebite cases occurring at 10 primary health centers in Houet Province from January 2014 to December 2018. Data were collected from the patient consultation recording database registry system.

Results

Affected individuals had a male/female ratio of 1.31. The lowest annual incidences (0.02 [95% CI –0.01 to 0.05] and 0.24 [95% CI 0.05 to 0.43]) were observed in the urban primary health centers of Bolomakoté and Sarfalao, respectively. Rural primary health centers in Nasso in 2016 and in Soumousso in 2014 had the highest annual incidence (13.80 [95% CI 7.59 to 20.00] and 3.92 [95% CI 2.99 to 4.86], respectively). Of the 664 registered snakebite victims, none received antivenom immunotherapy treatment.

Conclusion

Our study shows that snakebite envenomation incidents are common at the 10 primary health centers in Houet Province. Furthermore, despite the lack of antivenom and often inadequate treatment at these primary health centers, they remain the first point of care for snakebite victims.

Promoting co-existence between humans and venomous snakes through increasing the herpetological knowledge base

Snakebite incidence at least partly depends on the biology of the snakes involved. However, studies of snake biology have been largely neglected in favour of anthropic factors, with the exception of taxonomy, which has been recognised for some decades to affect the design of antivenoms. Despite this, within-species venom variation and the unpredictability of the correlation with antivenom cross-reactivity has continued to be problematic. Meanwhile, other aspects of snake biology, including behaviour, spatial ecology and activity patterns, distribution, and population demography, which can contribute to snakebite mitigation and prevention, remain underfunded and understudied. Here, we review the literature relevant to these aspects of snakebite and illustrate how demographic, spatial, and behavioural studies can improve our understanding of why snakebites occur and provide evidence for prevention strategies. We identify the large gaps that remain to be filled and urge that, in the future, data and relevant metadata be shared openly via public data repositories so that studies can be properly replicated and data used in future meta-analyses.

Snake Venom Identification via Fluorescent Discrimination

The identification and discrimination of snake venom are highly desired for timely clinical treatment. However, the complex components in snake venom make it a great challenge to achieve rapid and accurate identification. Inspired by the organism's taste sensing system, a fluorescent sensor array that could differentiate snake venoms was fabricated. The interaction of snake venoms with different fluorescent dyes in the sensor array gave rich information, based on which efficient detection of complex snake venom was achieved. The main six proteins of snake venom in the same concentration, different concentrations, and their mixtures were identified with 100% accuracy. Furthermore, seven snake venoms belonging to different snake families were discriminated in PBS buffer and human plasma. Interferents of bovine serum albumin (BSA), thrombin, and transferrin (TRF) demonstrated the practicability of the fluorescent sensor array. This strategy of a multiresponse sensor array provides an effective method for accurate and rapid venom toxicology analysis, benefiting early and timely clinical diagnosis and treatment.

Ethnozoology of snakebite victims in a risk area in Northeast Brazil

This study had the objectives to describe and analyze the perceptions and attitudes of snakebite victims in the semi-arid region of Northeast Brazil. A semi-structured questionnaire was applied as snakebite victims to identify the characteristics of the accident, their daily life, as well as positive and negative attitudes towards snake conservation and knowledge about species. Information about the possible uses of traditional treatment, allopathic care characteristics along with the symptoms and sequelae resulting from the accident were also recorded. The results obtained revealed that accidents mostly occurred during the development of their daily activities (i.e. during agricultural activities, in hunting activities in the mountains, in caring for farm animals, etc); most accidents are associated with Caatinga lancehead (Jararaca; Bothrops erythromelas); the bites usually affect the limbs, 75% (n = 46) feet, and the victims resort to medical assistance for specific treatment, although some seek this service after using or ingesting medicinal or popular/home-made therapeutic resources. The most relevant characteristics detected in these accidents were the strong influence of myths about traditional treatment (20%, n = 12) and the knowledge about identifying common snake species in the region (66%, n = 40). No perception was detected about the importance of these animals, but there were negative attitudes when finding a snake, fear/panic (34%, n = 21); kill the snake (23%, n = 14), thus constituting facts which may be related to the deficiency in the education level of this population which is interfering in environmental and public health issues. Work on improving the knowledge and local perception could subsidize actions and policies aimed to prevent accidents, demystify snakes and contribute to the conservation of the species.

Pain modulated by Bothrops snake venoms: Mechanisms of nociceptive signaling and therapeutic perspectives

Snake venoms are substances mostly composed by proteins and peptides with high biological activity. Local and systemic effects culminate in clinical manifestations induced by these substances. Pain is the most uncomfortable condition, but it has not been well investigated. This review discusses Bothrops snakebite-induced nociception, highlighting molecules involved in the mediation of this process and perspectives in treatment of pain induced by Bothrops snake venoms (B. alternatus, B. asper, B. atrox, B. insularis, B. jararaca, B. pirajai, B. jararacussu, B. lanceolatus, B. leucurus, B. mattogrossensis, B. moojeni). We highlight, the understanding of the nociceptive signaling, especially in snakebite, enables more efficient treatment approaches. Finally, future perspectives for pain treatment concerning snakebite patients are discussed.

Prospects and Challenges of Developing Plant-Derived Snake Antivenin Natural Products: A Focus on West Africa

Snakebite envenomation (SBE) is an important public health issue that is now receiving renewed attention following its reclassification as a Neglected Tropical Disease (NTD). Most incidences occur in rural areas of resource-limited countries, as such, timely and appropriate medical care for SBE is often inaccessible. The administration of anti-snake venom serum (ASV) is the only effective definitive treatment of SBE, but treatment failure to available ASVs is not uncommon. Emerging evidence highlights the potential of small-molecule compounds as inhibitors against toxins of snake venom. This presents an encouraging prospect to develop an alternative therapeutic option for the treatment SBE, that may be amenable for use at the point of care in resource-constraint settings. In view of the pivotal role of natural products in modern drug discovery programmes, there is considerable interest in ethno-pharmacological mining of medicinal plants and plant-derived medicinal compounds toward developing novel snake venom-neutralising therapeutics. In this review, we compile a collection of medicinal plants used in the treatment of SBE in West Africa and highlight their promise as potential botanical drugs or as sources of novel small-molecule compounds for the treatment of SBE. The challenges that must be surmounted to bring this to fruition including the need for (sub) regional collaboration have been discussed.

Surgical Management of Patients with Snakebite-Related Musculoskeletal Complication-A Single Institution Experience in Cambodia

BACKGROUND

Snakebite-related injury is a serious public health issue. In Cambodia, it is estimated that up to 21,500 cases of envenoming occurs from snakebites annually. Musculoskeletal disability is a major long-term complication associated with the injury. In this study, we aim to describe surgical management and rehabilitation in snakebite-related musculoskeletal injuries at Children's Surgical Centre, Phnom Penh, Cambodia.

METHODS

We conducted a retrospective case series analysis of patients with snakebite-related injury who were treated between January 1, 2002 and December 31, 2018. Surgical patients were divided into the early and late presenting groups (= < one year vs. > one year, respectively) based on their time interval from snake bite to time of presentation.

RESULTS

There were 88 patients who presented with snakebite-related musculoskeletal injury during the cohort study period. Majority of them were male (n = 62, 71%) and had a median age of 24 years old (IQR 17-44). The injuries were all in the upper and lower limbs though lower limb injury was more common in female patients (81% vs. 48%, Fisher's test p = 0.005). The median time interval from snakebite to time of treatment was 3 years (IQR 3 months-11 years). In this study, 65 patients received surgical interventions. An ulcerated wound was the most common symptom among the early presenting group (78% vs. 24%), while scar contracture was most common among the late group (76% vs. 22%) (Fisher's test p < 0.0001). For management, surgical debridement was the most common primary intervention for the early group (52% vs. 19%), and contracture release was the most common for patients in the late group (62% vs. 15%) (Fisher's test p = 0.0004). Overall, the postoperative complication rate was highest in the late presenting group (34% vs. 3%, Fisher's test p = 0.005).

CONCLUSION

More than half of the patients presented with musculoskeletal injury require surgical correction. Our study demonstrated that scar contracture is the most common complaint among the late presenting group and is associated with high postoperative complication rate.

Climate change and the increase of human population will threaten conservation of Asian cobras

Asian cobras (genus Naja) are venomous snakes distributed from the Middle East to Southeast Asia. Because cobras often live near humans settlements, they are responsible for a large part of snakebite incidents and as such pose a challenge for public health systems. In the light of growing human populations, correctly mapping the present and future ranges of Asian cobras is therefore important for both biological conservation and public health management. Here, we mapped the potential climatic niches of ten Asian cobra species for both the present and the future, with the aim to quantify changes in climate and human population densities relative to their current and future ranges. Our analyses reveal that cobras that are adapted to dry climates and inhabit islands have narrow climatic niches, while those of mainland species with larger geographic ranges are much wider. We also found a higher degree of fragmentation of future cobra distributions; within the next 50 years, Asian cobras will lose an average of around 60% of their current suitable climatic range. In the near future, Naja mandalayensis, N. sputatrix, N. samarensis, and N. philippinensis are likely to have no accessible suitable climate space left. Besides, a further increase of human populations in this region may also exponentially accelerate the effects of anthropogenic impacts. Solutions for conservation may involve awareness and appropriate use of law to overcome the rate of habitat degradation and the increase of animal trade of Asian cobras, while promoting investment on health systems to avoid snakebite fatalities.

Snakebites in Rural Areas of Brazil by Race: Indigenous the Most Exposed Group

Animal stings are environmental hazards that threaten millions annually and cause a significant socioeconomic impact. Snakebite envenoming affects 2.7 million people globally every year, mostly the poorest and rural communities, with approximately 27,000 annual cases in Brazil. This study’s objective is to identify the most exposed racial group for snakebites in rural areas of Brazil and analyze possible differences in the outcome of an accident. A retrospective epidemiological study was conducted using a database of rural snakebite cases from Brazil’s Ministry of Health (2017). Descriptive analysis and a regression model were performed to examine the association of bad outcomes after a snakebite with several covariables. While mixed-race individuals presented the highest number of cases (61.79%), indigenous and white populations were the racial groups with the highest and lowest exposure rates (194.3 and 34.1 per 100,000 population, respectively). The fatality rate was 3.5 times higher in the indigenous population compared to the white population. In the multivariable model, the number of hours between the accident and health care received and the case classification suggested an association with a bad outcome. Snakebite is prominent in Brazil, particularly among indigenous groups. Antivenom is available in the Brazilian Health System; however, efforts need to be made for decentralization.

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.

Neurotoxic snake bite in pregnancy

Neurotoxic snake bites may cause paralysis within 1-8 h. Appropriate management includes early and adequate volumes of antivenom as well as ventilatory support. This case study describes the management of a pregnant woman who was bitten on a farm in rural South Africa and transferred to an academic hospital, 300 km away. An approach to the management of snake bites in pregnancy is discussed as well as a review of the current known literature of venomous snakes and the use of antivenom in pregnancy. This report aims to encourage further reporting of snake bites in pregnancy.

Burden of disease among the world's poorest billion people: An expert-informed secondary analysis of Global Burden of Disease estimates

Background

The health of populations living in extreme poverty has been a long-standing focus of global development efforts, and continues to be a priority during the Sustainable Development Goal era. However, there has not been a systematic attempt to quantify the magnitude and causes of the burden in this specific population for almost two decades. We estimated disease rates by cause for the world’s poorest billion and compared these rates to those in high-income populations.

Methods

We defined the population in extreme poverty using a multidimensional poverty index. We used national-level disease burden estimates from the 2017 Global Burden of Disease Study and adjusted these to account for within-country variation in rates. To adjust for within-country variation, we looked to the relationship between rates of extreme poverty and disease rates across countries. In our main modeling approach, we used these relationships when there was consistency with expert opinion from a survey we conducted of disease experts regarding the associations between household poverty and the incidence and fatality of conditions. Otherwise, no within-country variation was assumed. We compared results across multiple approaches for estimating the burden in the poorest billion, including aggregating national-level burden from the countries with the highest poverty rates. We examined the composition of the estimated disease burden among the poorest billion and made comparisons with estimates for high-income countries.

Results

The composition of disease burden among the poorest billion, as measured by disability-adjusted life years (DALYs), was 65% communicable, maternal, neonatal, and nutritional (CMNN) diseases, 29% non-communicable diseases (NCDs), and 6% injuries. Age-standardized DALY rates from NCDs were 44% higher in the poorest billion (23,583 DALYs per 100,000) compared to high-income regions (16,344 DALYs per 100,000). Age-standardized DALY rates were 2,147% higher for CMNN conditions (32,334 DALYs per 100,000) and 86% higher for injuries (4,182 DALYs per 100,000) in the poorest billion, compared to high-income regions.

Conclusion

The disease burden among the poorest people globally compared to that in high income countries is highly influenced by demographics as well as large disparities in burden from many conditions. The comparisons show that the largest disparities remain in communicable, maternal, neonatal, and nutritional diseases, though NCDs and injuries are an important part of the “unfinished agenda” of poor health among those living in extreme poverty.

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.

Perceptions, awareness on snakebite envenoming among the tribal community and health care providers of Dahanu block, Palghar District in Maharashtra, India

INTRODUCTION

India has remarkably the highest number of snakebite cases contributing to nearly 50% of the global snakebite deaths. Despite this fact, there is limited knowledge and awareness regarding the management practices for snakebite in the Indian population. The study aimed to explore the knowledge, awareness, and perception of snakes and snakebites, first aid, and treatment amongst the community and the frontline health workers in a tribal block of Dahanu, Maharashtra, India.

METHODS

A cross-sectional study was carried out from June 2016 to October 2018 in the Dahanu Block, Maharashtra. Perceptions, knowledge, awareness, and first-aid practices on the snakebites among the community were studied through focus group discussions (FGDs). Semi-structured questionnaires were used to assess the knowledge, awareness, and experience of the traditional faith healers, snake rescuers, frontline health workers on the snakebites and their management. A facility check survey was conducted using pre-tested questionnaires for different levels of the government health care facilities.

RESULTS

Most of the tribal community was aware of the commonly found snakes and their hiding places. However, there was inadequate knowledge on the identification and classification of venomous snakes. Belief in a snake god, the perception that snakes will not come out during thunderstorms, change in taste sensation, the ability of tamarind seeds or magnet to reduce the venom effect were some of the superstitions reported by the tribal community. The application of a harmful method (Tourniquet) as the first aid for snakebite was practiced by the tribal community. They preferred herbal medicines and visiting the traditional faith healers before shifting the patient to the government health facility. The knowledge on the ability to identify venomous snakebites and anti-venom was significantly higher amongst nurses and accredited social health activists (ASHAs) than auxiliary nurse midwives (ANMs) and multi-purpose workers (MPWs) (p < 0.05). None of the traditional faith healers; but nearly 60% of snake rescuers were aware of anti-venom. Fifty percent of the medical officers in Dahanu block did not have correct knowledge about the Krait bite symptoms, and renal complications due to the Russell viper bite.

CONCLUSIONS

Inappropriate perception, inadequate awareness, and knowledge about snakes and snakebites may predispose the tribal community to increased risks of venomous snakebites. Unproven and harmful methods for snakebite treatment practiced by the community and traditional faith healers could be dangerous leading to high mortality. Therefore, a multi-sectoral approach of community awareness, mapping of vulnerable populations, capacity building of health care facility, empowerment of health care workers (HCWs) could be useful for reducing the mortality and morbidity due to snakebite envenoming in India.

Integrating lay knowledge and practice into snakebite prevention and care in central Africa, a hotspot for envenomation

The WHO has identified the goal of halving deaths and disability from snakebite envenomation (SBE) by 2030 through a four-pillar program that promotes accessible and affordable treatments, strengthens health systems, promotes community and multi-level engagement, and mobilizes partnerships, coordination and resources to advocate for global action. This initiative could accelerate multi-disciplinary research and action in central Africa, a “hotspot” for SBE, but it offers little specific guidance about anthropological research to be conducted. This commentary develops that research agenda. It surveys anthropological, ethnohistorical investigations in the central African forest to elaborate the socio-cultural and historical significance and practices around snakes and snakebites. It draws from south and southeast Asian and Latin American literatures to illustrate anthropological contributions to SBE research. It then outlines a Central African research agenda employing ethnobiological investigation of snake ecologies, participatory evaluations of humans-snake contacts, and interviews and participant-observation of local prevention and treatment practices and knowledge. This research will co-develop policies and practices with forest communities and leaders and regional and national authorities to reduce the burden of SBE.

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Central African forests are a hotspot for snakebite envenomation.

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SBE research in central Africa has not mobilized anthropological literatures or methodologies.

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Policies to reduce SBE burden in central Africa should build on participatory research.

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Policies to reduce SBE burden should be co-developed with local and national stakeholders.

The Burden of Snakebite in Rural Communities in Kenya: A Household Survey

Annually, about 2.7 million snakebite envenomings occur worldwide, primarily affecting those living in rural regions. Effective treatment exists but is scarce, and traditional treatments are commonly used. To inform context-specific policies in Kenya, this study aimed to determine the health-seeking behavior and the health, social, and economic burden of snakebites in rural communities. Nonprobability sampling was used to survey 382 respondents from four snakebite-endemic counties, from February to August 2020, using a structured questionnaire. Descriptive statistics, Fisher's exact tests, binary logistic regressions, and Mantel-Haenszel tests were used for analysis. Life-time experience with snakebites included 13.1% of respondents who reported being personally bitten and 37.4% who reported knowing of a community member being bitten. Respondents reported death after a snakebite in 9.1% of bitten community members and in 14.6% of bitten family members. Risk of snakebite was not significantly associated with sex, educational level, or occupation. Snakebite victims were most often walking (38%) or farming (24%) when bitten. Of those bitten, 58% went to a health facility, 30% sought traditional treatment, and 12% first went to a traditional healer before visiting a facility. Significant differences existed in perceptions on the financial consequences of snakebites among those who had been personally bitten and those who had observed a snakebite. Most commonly mentioned preventive measures were wearing shoes and carrying a light in the dark. Community engagement, including engagement with traditional healers, is needed to reduce snakebites. This should be done through education and sensitization to improve used preventive measures and effective health-seeking behavior.

Snakebite incidents, prevention and care during COVID-19: Global key-informant experiences

Snakebite envenoming is a long-neglected disease causing significant morbidity and mortality in snakebite endemic low- and middle-income countries (LMICs). Global awareness on snakebite was increasing steadily up to 2020, and an increasing number of countries began to acknowledge the issue, when coronavirus disease 2019 (COVID-19) started to have an unprecedented impact on societies and health systems. To better understand how snakebite incidents, prevention and care are being affected during this global emergency, we collected perspectives of snakebite community- and health system stakeholders in a qualitative key-informant study. An open-ended survey and semi-structured interviews were conducted to gather information on changes in snakebite occurrence and circumstances, community responses, access to care and health outcomes in LMICs since the COVID-19 pandemic. Forty-three informants from 21 countries participated in the study. Based on informants' experiences, in spite of COVID-19 lockdowns, exposure to snakes did not change in many rural agrarian communities, where incidences are usually highest. However, we did find several access to care issues relating to avoidance of formal care, transport barriers, overburdened healthcare systems and -providers, and antivenom manufacturing and supply disruptions, which were unique per context. On a brighter note, ventilator availability had increased in several countries, although not automatically benefitting snakebite patients directly. In conclusion, we found apparent effects of the COVID-19 pandemic on snakebite prevention and care, although its severity was highly context- and time-dependent. Interactions between the pandemic effects and snakebite incidents most severely impact remote rural communities, showing the need to invest in community-based prevention and care.

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The COVID-19 pandemic has impacted snakebite prevention and care in LMICs.

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Healthcare avoidance and transport barriers have resulted in additional morbidity and mortality.

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Increased ventilator availability could have a positive effect on snakebite care in specific settings.

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Treatment of snakebites at primary level health facilities can significantly reduce snakebite morbidity and mortality.

Distance to available services for newborns at facilities in Malawi: A secondary analysis of survey and health facility data

Background

Malawi has halved the neonatal mortality rate between 1990–2018, however, is not on track to achieve the Sustainable Development Goal 12 per 1,000 live births. Despite a high facility birth rate (91%), mother-newborn dyads may not remain in facilities long enough to receive recommended care and quality of care improvements are needed to reach global targets. Physical access and distance to health facilities remain barriers to quality postnatal care.

Methods

Using data We used individual data from the 2015–16 Malawi Demographic and Health Survey and facility data from the 2013–14 Malawi Service Provision Assessment, linking households to all health facilities within specified distances and travel times. We calculated service readiness scores for facilities to measure their capacity to provide birth/newborn care services. We fitted multi-level regression models to evaluate the association between the service readiness and appropriate newborn care (receiving at least five of six interventions).

Results

Households with recent births (n = 6010) linked to a median of two birth facilities within 5–10 km and one facility within a two-hour walk. The maximum service environment scores for linked facilities median was 77.5 for facilities within 5–10 km and 75.5 for facilities within a two-hour walk. While linking to one or more facilities within 5-10km or a two-hour walk was not associated with appropriate newborn care, higher levels of service readiness in nearby facilities was associated with an increased risk of appropriate newborn care.

Conclusions

Women’s choice of nearby facilities and quality facilities is limited. High quality newborn care is sub-optimal despite high coverage of facility birth and some newborn care interventions. While we did not find proximity to more facilities was associated with increased risk of appropriate care, high levels of service readiness was, showing facility birth and improved access to well-prepared facilities are important for improving newborn care.

Mutual enlightenment: A toolbox of concepts and methods for integrating evolutionary and clinical toxinology via snake venomics and the contextual stance

Snakebite envenoming is a neglected tropical disease that may claim over 100,000 human lives annually worldwide. Snakebite occurs as the result of an interaction between a human and a snake that elicits either a defensive response from the snake or, more rarely, a feeding response as the result of mistaken identity. Snakebite envenoming is therefore a biological and, more specifically, an ecological problem. Snake venom itself is often described as a "cocktail", as it is a heterogenous mixture of molecules including the toxins (which are typically proteinaceous) responsible for the pathophysiological consequences of envenoming. The primary function of venom in snake ecology is pre-subjugation, with defensive deployment of the secretion typically considered a secondary function. The particular composition of any given venom cocktail is shaped by evolutionary forces that include phylogenetic constraints associated with the snake's lineage and adaptive responses to the snake's ecological context, including the taxa it preys upon and by which it is predated upon. In the present article, we describe how conceptual frameworks from ecology and evolutionary biology can enter into a mutually enlightening relationship with clinical toxinology by enabling the consideration of snakebite envenoming from an "ecological stance". We detail the insights that may emerge from such a perspective and highlight the ways in which the high-fidelity descriptive knowledge emerging from applications of -omics era technologies - "venomics" and "antivenomics" - can combine with evolutionary explanations to deliver a detailed understanding of this multifactorial health crisis.

Citizen science and online data: Opportunities and challenges for snake ecology and action against snakebite

The secretive behavior and life history of snakes makes studying their biology, distribution, and the epidemiology of venomous snakebite challenging. One of the most useful, most versatile, and easiest to collect types of biological data are photographs, particularly those that are connected with geographic location and date-time metadata. Photos verify occurrence records, provide data on phenotypes and ecology, and are often used to illustrate new species descriptions, field guides and identification keys, as well as in training humans and computer vision algorithms to identify snakes. We scoured eleven online and two offline sources of snake photos in an attempt to collect as many photos of as many snake species as possible, and attempt to explain some of the inter-species variation in photograph quantity among global regions and taxonomic groups, and with regard to medical importance, human population density, and range size. We collected a total of 725,565 photos-between 1 and 48,696 photos of 3098 of the world's 3879 snake species (79.9%), leaving 781 "most wanted" species with no photos (20.1% of all currently-described species as of the December 2020 release of The Reptile Database). We provide a list of most wanted species sortable by family, continent, authority, and medical importance, and encourage snake photographers worldwide to submit photos and associated metadata, particularly of "missing" species, to the most permanent and useful online archives: The Reptile Database, iNaturalist, and HerpMapper.

Dealing with snakebite in rural Cameroon: A qualitative investigation among victims and traditional healers

BACKGROUND

Snakebite is a neglected tropical disease (NTD) affecting rural and remote populations globally, who are additionally burdened by poverty and the lack of effective healthcare systems. Delayed healthcare and use of traditional treatments are very frequent. The purpose of our study was to explore perceptions of snakes, impact of snakebite, and knowledge and opinions of different snakebite treatments with the aim of identifying opportunities for improving snakebite management.

METHODS

This is a qualitative descriptive study based on semi-structured interviews with 21 snakebite victims and 4 traditional healers in 4 villages of Akonolinga health district, Center Region, Cameroon. Analysis focused on describing participants' perceptions of snakes, the impact of snakebite on the victims' lives, and their opinions of different treatment options.

RESULTS

Respondents were fearful of snakes and knowledgeable about envenoming symptoms and treatments. The experience of snakebite led to increased vigilance and avoidance behaviours, which sometimes resulted in financial loss for the victims. A range of traditional treatments were described, including tourniquets, black-stone application and medicinal plant decoctions. However, opinions were ambivalent regarding their efficacy, depending especially on previous personal experiences. Still, traditional treatments were said to be more available and cheaper than hospital care, and in particular, than antivenom. Nevertheless, most victims preferred hospital treatment if the financial and transportation barriers were lifted. Both snakebite victims and traditional healers were of the opinion that collaboration between health services and traditional healers could help to improve snakebite management and outcomes.

CONCLUSION

Our study shows that snakebite victims are in favour of using antivenom for the treatment of snakebite and would welcome better access to it. However, its current unavailability and high cost pushes them to turn to traditional treatments. On the other hand, traditional healers are in favour of collaborating with health facilities. These results are very encouraging for the improvement of snakebite management in Cameroon along the lines of the WHO Snakebite Envenoming Strategy for Prevention and Control: ensuring access to safe and effective treatment, and increasing partnership and coordination between communities, traditional healers, and conventional caregivers.

Erythrocyte haemotoxicity profiling of snake venom toxins after nanofractionation

Snakebite is classified as a priority Neglected Tropical Disease by the World Health Organization. Understanding the pathology of individual snake venom toxins is of great importance when developing more effective snakebite therapies. Snake venoms may induce a range of pathologies, including haemolytic activity. Although snake venom-induced erythrocyte lysis is not the primary cause of mortality, haemolytic activity can greatly debilitate victims and contributes to systemic haemotoxicity. Current assays designed for studying haemolytic activity are not suitable for rapid screening of large numbers of toxic compounds. Consequently, in this study, a high-throughput haemolytic assay was developed that allows profiling of erythrocyte lysis, and was validated using venom from a number of medically important snake species (Calloselasma rhodostoma, Daboia russelii, Naja mossambica, Naja nigricollis and Naja pallida). The assay was developed in a format enabling direct integration into nanofractionation analytics, which involves liquid chromatographic separation of venom followed by high-resolution fractionation and subsequent bioassaying (and optional proteomics analysis), and parallel mass spectrometric detection. Analysis of the five snake venoms via this nanofractionation approach involving haemolytic assaying provided venom-cytotoxicity profiles and enabled identification of the toxins responsible for haemolytic activity. Our results show that the elapid snake venoms (Naja spp.) contained both direct and indirect lytic toxins, while the viperid venoms (C. rhodostoma and D. russelii) only showed indirect lytic activities, which required the addition of phospholipids to exert cytotoxicity on erythrocytes. The haemolytic venom toxins identified were mainly phospholipase A2s and cytotoxic three finger toxins. Finally, the applicability of this new analytical method was demonstrated using a conventional snakebite antivenom treatment and a small-molecule drug candidate to assess neutralisation of venom cytotoxins.

Adjunct treatment in snakebite envenoming: a systematic review of randomised controlled trials

Adjunct therapy in snakebite may be lifesaving if administered appropriately or can be harmful if non-judicious use leads to avoidable delays in administering antivenom. This systematic review analyses the evidence from randomised controlled trials (RCTs) on the efficacy of adjunct treatment administered with antivenom. PubMed, EMBASE, Scopus, Cochrane library and CINAHL were searched for RCTs enrolling patients with snakebite envenoming where a treatment other than antivenom has been assessed for its efficacy within the last 25 y. Fifteen studies met the inclusion criteria. The interventions assessed were categorised as adjunct therapies (heparin or fresh frozen plasma) to reverse haemotoxicity (three studies), antibiotics to prevent local infections (three studies), steroids to reduce local swelling (one study), premedication (adrenaline, steroids and antihistamines, either alone or in combination) to reduce hypersensitivity reactions to antivenom (five studies) and other interventions (three studies). Apart from a beneficial effect of low-dose adrenaline (1:1000, 0.25 ml administered subcutaneously) in preventing antivenom-induced hypersensitivities (OR: 0.54, 95% CI 0.32 to 0.93, two RCTs, 354 participants, moderate certainty evidence) in Sri Lanka, evidence for any other adjunct therapy is either non-existent or needs confirmation by larger better designed trials.

An exploratory focus group study on experiences with snakebites: health-seeking behaviour and challenges in rural communities of Kenya

BACKGROUND

Snakebite envenoming is a long-hidden public health threat in the rural communities of Kenya. This study aimed to shed light on the health-seeking behaviour of people bitten by snakes, views on prevention measures and community needs and the consequences for snakebite patients in these areas.

METHODS

Six focus group interviews were conducted in communities in the Kajiado (n=3) and Kilifi (n=3) counties.

RESULTS

Traditional first-aid practices such as the use of a tourniquet and/or cutting the wound, use of a black stone and a variety of other traditional remedies were common. Challenges with transportation to health facilities and inadequately resourced facilities complicated accessing medical care. Community members voiced a need to improve access to trained healthcare workers and snakebite treatments at health facilities.

CONCLUSION

While communities had high trust in evidence-based medical care, traditional treatment was often sought, causing delays in timely medical attention. Traditional practices were often used in the home environment and these were not usually administered by a traditional healer. The findings illustrate the need to combine improving the availability of effective snakebite treatment and healthcare worker training on snakebite with community education to reduce the impact of snakebite.

Preclinical validation of a repurposed metal chelator as an early-intervention therapeutic for hemotoxic snakebite

Snakebite envenoming causes 138,000 deaths annually, and ~400,000 victims are left with permanent disabilities. Envenoming by saw-scaled vipers (Viperidae: Echis) leads to systemic hemorrhage and coagulopathy and represents a major cause of snakebite mortality and morbidity in Africa and Asia. The only specific treatment for snakebite, antivenom, has poor specificity and low affordability and must be administered in clinical settings because of its intravenous delivery and high rates of adverse reactions. This requirement results in major treatment delays in resource-poor regions and substantially affects patient outcomes after envenoming. Here, we investigated the value of metal ion chelators as prehospital therapeutics for snakebite. Among the tested chelators, dimercaprol (British anti-Lewisite) and its derivative 2,3-dimercapto-1-propanesulfonic acid (DMPS) were found to potently antagonize the activity of Zn²⁺-dependent snake venom metalloproteinases in vitro. Moreover, DMPS prolonged or conferred complete survival in murine preclinical models of envenoming against a variety of saw-scaled viper venoms. DMPS also considerably extended survival in a "challenge and treat" model, where drug administration was delayed after venom injection and the oral administration of this chelator provided partial protection against envenoming. Last, the potential clinical scenario of early oral DMPS therapy combined with a delayed, intravenous dose of conventional antivenom provided prolonged protection against the lethal effects of envenoming in vivo. Our findings demonstrate that the safe and affordable repurposed metal chelator DMPS can effectively neutralize saw-scaled viper venoms in vitro and in vivo and highlight the promise of this drug as an early, prehospital, therapeutic intervention for hemotoxic snakebite envenoming.

Implications of global environmental change for the burden of snakebite

Snakebite envenoming is a set of intoxication diseases that disproportionately affect people of poor socioeconomic backgrounds in tropical countries. As it is highly dependent on the environment its burden is expected to shift spatially with global anthropogenic environmental (climate, land use) and demographic change. The mechanisms underlying the changes to snakebite epidemiology are related to factors of snakes and humans. The distribution and abundance of snakes are expected to change with global warming via their thermal tolerance, while rainfall may affect the timing of key activities like feeding and reproduction. Human population growth is the primary cause of land-use change, which may impact snakes at smaller spatial scales than climate via habitat and biodiversity loss (e.g. prey availability). Human populations, on the other hand, could experience novel patterns and morbidity of snakebite envenoming, both as a result of snake responses to environmental change and due to the development of agricultural adaptations to climate change, socioeconomic and cultural changes, development and availability of better antivenoms, personal protective equipment, and mechanization of agriculture that mediate risk of encounters with snakes and their outcomes. The likely global effects of environmental and demographic change are thus context-dependent and could encompass both increasing and or snakebite burden (incidence, number of cases or morbidity), exposing new populations to snakes in temperate areas due to “tropicalization”, or by land use change-induced snake biodiversity loss, respectively. Tackling global change requires drastic measures to ensure large-scale ecosystem functionality. However, as ecosystems represent the main source of venomous snakes their conservation should be accompanied by comprehensive public health campaigns. The challenges associated with the joint efforts of biodiversity conservation and public health professionals should be considered in the global sustainability agenda in a wider context that applies to neglected tropical and zoonotic and emerging diseases.

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Distribution and abundance of snakes are expected to be affected by climate change.

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Land-use change may also impact snakes but at smaller spatial scales than climate.

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Human populations could experience novel patterns and morbidity of snakebite.

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Reducing snakebite should be accompanied by actions that protect snake diversity.

Venom-Induced Blood Disturbances by Palearctic Viperid Snakes, and Their Relative Neutralization by Antivenoms and Enzyme-Inhibitors

Palearctic vipers are medically significant snakes in the genera Daboia, Macrovipera, Montivipera, and Vipera which occur throughout Europe, Central Asia, Near and Middle East. While the ancestral condition is that of a small-bodied, lowland species, extensive diversification has occurred in body size, and niche specialization. Using 27 venom samples and a panel of in vitro coagulation assays, we evaluated the relative coagulotoxic potency of Palearctic viper venoms and compared their neutralization by three antivenoms (Insoserp Europe, VIPERFAV and ViperaTAb) and two metalloprotease inhibitors (prinomastat and DMPS). We show that variation in morphology parallels variation in the Factor X activating procoagulant toxicity, with the three convergent evolutions of larger body sizes (Daboia genus, Macrovipera genus, and Vipera ammodytes uniquely within the Vipera genus) were each accompanied by a significant increase in procoagulant potency. In contrast, the two convergent evolutions of high altitude specialization (the Montivipera genus and Vipera latastei uniquely within the Vipera genus) were each accompanied by a shift away from procoagulant action, with the Montivipera species being particularly potently anticoagulant. Inoserp Europe and VIPERFAV antivenoms were both effective against a broad range of Vipera species, with Inoserp able to neutralize additional species relative to VIPERFAV, reflective of its more complex antivenom immunization mixture. In contrast, ViperaTAb was extremely potent in neutralizing V. berus but, reflective of this being a monovalent antivenom, it was not effective against other Vipera species. The enzyme inhibitor prinomastat efficiently neutralized the metalloprotease-driven Factor X activation of the procoagulant venoms. In contrast, DMPS (2,3-dimercapto-1-propanesulfonic acid), which as been suggested as another potential treatment option in the absence of antivenom, DMPS failed against all venoms tested. Overall, our results highlight the evolutionary variations within Palearctic vipers and help to inform clinical management of viper envenomation.

Evaluating spatiotemporal dynamics of snakebite in Sri Lanka: Monthly incidence mapping from a national representative survey sample

BACKGROUND

Snakebite incidence shows both spatial and temporal variation. However, no study has evaluated spatiotemporal patterns of snakebites across a country or region in detail. We used a nationally representative population sample to evaluate spatiotemporal patterns of snakebite in Sri Lanka.

METHODOLOGY

We conducted a community-based cross-sectional survey representing all nine provinces of Sri Lanka. We interviewed 165 665 people (0.8% of the national population), and snakebite events reported by the respondents were recorded. Sri Lanka is an agricultural country; its central, southern and western parts receive rain mainly from Southwest monsoon (May to September) and northern and eastern parts receive rain mainly from Northeast monsoon (November to February). We developed spatiotemporal models using multivariate Poisson process modelling to explain monthly snakebite and envenoming incidences in the country. These models were developed at the provincial level to explain local spatiotemporal patterns.

PRINCIPAL FINDINGS

Snakebites and envenomings showed clear spatiotemporal patterns. Snakebite hotspots were found in North-Central, North-West, South-West and Eastern Sri Lanka. They exhibited biannual seasonal patterns except in South-Western inlands, which showed triannual seasonality. Envenoming hotspots were confined to North-Central, East and South-West parts of the country. Hotspots in North-Central regions showed triannual seasonal patterns and South-West regions had annual patterns. Hotspots remained persistent throughout the year in Eastern regions. The overall monthly snakebite and envenoming incidences in Sri Lanka were 39 (95%CI: 38-40) and 19 (95%CI: 13-30) per 100 000, respectively, translating into 110 000 (95%CI: 107 500-112 500) snakebites and 45 000 (95%CI: 32 000-73 000) envenomings in a calendar year.

CONCLUSIONS/SIGNIFICANCE

This study provides information on community-based monthly incidence of snakebites and envenomings over the whole country. Thus, it provides useful insights into healthcare decision-making, such as, prioritizing locations to establish specialized centres for snakebite management and allocating resources based on risk assessments which take into account both location and season.

Proximity between humans and a highly medically significant snake, Russell's viper, in a tropical rural community

Snakebite envenoming is a major neglected tropical health issue. The high incidence of snakebites in tropical rural communities suggests that venomous snakes and people are often in proximity but quantitative evidence is lacking. I used radio-telemetry on a population of Russell's vipers (Daboia russelii), one of the most medically important snakes in the world, to quantify proximity between this venomous snake and people and estimate susceptibility to snakebite envenoming in India. I observed people ≤50 m of a radio-equipped viper in ~17% of 2,066 snake relocations. People were more frequently observed in proximity to Russell's vipers in January and July compared to March, but all other contrasts were statistically similar. This pattern indicates that snakebite incidence, which peaks in summer in the study area, is not particularly linked to the encounter frequency between people and vipers. However, consistent with epidemiological data plantation workers were the most at-risk part of the population. By integrating information about the locations of humans and snakes in space and time, this pioneering research highlights the need to include snake ecology into the study of the human-venomous-snake conflict, and provides a model approach to help mitigate the burden caused by venomous snakes in the rural Tropics.

Drought, desertification and poverty: A geospatial analysis of snakebite envenoming in the Caatinga biome of Brazil

Epidemiological data on snakebite in the Brazilian state of Ceará are scarce, as the only report on this subject was last published in 1997. However, according to the Brazilian system of recording disease incidents (Sistema de Informação de Agravos de Notificação [SINAN]), more than 13,000 snakebites have been registered since 2001 in the state of Ceará, making this disease an important public health issue. In the present study, we evaluate the influence of environmental changes, including drought and desertification, on the risk of snakebite envenoming in the Brazilian northeastern state of Ceará. We compare public data on snakebites from Brazilian Epidemiological Surveillance System (DATASUS), rainfall records, advanced desertification maps, pastures and socioeconomic information of the 184 municipals in Ceará between 2001 and 2017. During the period of investigation, 8,945 snakebites were recorded, the majority (93.8%) of which involved venomous snakes. Almost half of the municipals (48%) had 100 incidences or more per 100,000 inhabitants. Data collected also highlight month-to-month occurrences of snakebites, with trends to rise shortly after the onset of precipitation, peaking in July and then trending downward as rainfall decreases, reaching the lowest level in December. We deduce an inverse relationship between Human Development Index (HDI) and snakebites per area. Spearman correlation and principal component analysis support the hypothesis that water scarcity and desertification are linked to increased risk of snakebite envenoming. Our study indicates that besides poverty, dry and desertified areas represent risk factors associated with increased incidence of snakebite envenoming in the state of Ceará.

Snakebite Envenoming Diagnosis and Diagnostics

Snakebite envenoming is predominantly an occupational disease of the rural tropics, causing death or permanent disability to hundreds of thousands of victims annually. The diagnosis of snakebite envenoming is commonly based on a combination of patient history and a syndromic approach. However, the availability of auxiliary diagnostic tests at the disposal of the clinicians vary from country to country, and the level of experience within snakebite diagnosis and intervention may be quite different for clinicians from different hospitals. As such, achieving timely diagnosis, and thus treatment, is a challenge faced by treating personnel around the globe. For years, much effort has gone into developing novel diagnostics to support diagnosis of snakebite victims, especially in rural areas of the tropics. Gaining access to affordable and rapid diagnostics could potentially facilitate more favorable patient outcomes due to early and appropriate treatment. This review aims to highlight regional differences in epidemiology and clinical snakebite management on a global scale, including an overview of the past and ongoing research efforts within snakebite diagnostics. Finally, the review is rounded off with a discussion on design considerations and potential benefits of novel snakebite diagnostics.

Anticoagulant Activity of Naja nigricollis Venom Is Mediated by Phospholipase A2 Toxins and Inhibited by Varespladib

Bites from elapid snakes typically result in neurotoxic symptoms in snakebite victims. Neurotoxins are, therefore, often the focus of research relating to understanding the pathogenesis of elapid bites. However, recent evidence suggests that some elapid snake venoms contain anticoagulant toxins which may help neurotoxic components spread more rapidly. This study examines the effects of venom from the West African black-necked spitting cobra (Naja nigricollis) on blood coagulation and identifies potential coagulopathic toxins. An integrated RPLC-MS methodology, coupled with nanofractionation, was first used to separate venom components, followed by MS, proteomics and coagulopathic bioassays. Coagulation assays were performed on both crude and nanofractionated N. nigricollis venom toxins as well as PLA₂s and 3FTx purified from the venom. Assays were then repeated with the addition of either the phospholipase A₂ inhibitor varespladib or the snake venom metalloproteinase inhibitor marimastat to assess whether either toxin inhibitor is capable of neutralizing coagulopathic venom activity. Subsequent proteomic analysis was performed on nanofractionated bioactive venom toxins using tryptic digestion followed by nanoLC-MS/MS measurements, which were then identified using Swiss-Prot and species-specific database searches. Varespladib, but not marimastat, was found to significantly reduce the anticoagulant activity of N. nigricollis venom and MS and proteomics analyses confirmed that the anticoagulant venom components mostly consisted of PLA₂ proteins. We, therefore, conclude that PLA₂s are the most likely candidates responsible for anticoagulant effects stimulated by N. nigricollis venom.

Antihyaluronidase and Alkaline Phosphatase (ALP) Activities of Medicinal Plants to Combat Echis carinatus Venom-Induced Toxicities

Snakebite is one of the most neglected diseases of developing countries. Deaths due to snakebite envenoming are quite high in Pakistan, and many deaths are caused by Echis carinatus envenomation. Traditional use of medicinal plants against snakebites is a common practice in Pakistan due to countless benefits. The current study was performed with the objective to evaluate eighteen Pakistani medicinal plants inhibitory potential against hyaluronidase and alkaline phosphatase enzymes of Pakistani Echis carinatus venom. Hyaluronidase activity (0.2-1.6 mg/0.1 mL) and alkaline phosphatase activity (0.1-0.8 mg/0.1 mL) were measured in dose-dependent manner. Crude methanolic extracts of medicinal plants were used for in vitro investigation of their inhibitory activity against toxic enzymes. All active plants were fractioned using different solvents and were again analyzed for inhibitory activity of same enzymes. Results indicated all plants were able to neutralize hyaluronidase that Swertia chirayita (Roxb. ex Flem.) Karst., Terminalia arjuna Wight and Arn, Rubia cordifolia Thumb., and Matthiola incana (L.) R.Br. inhibited maximum hyaluronidase activity equivalent to standard reference (p > 0.5). Pakistani medicinal plants are dense with natural neutralizing metabolites and other active phytochemicals which could inhibit hyaluronidase activity of Pakistani Echis carinatus venom. Further advanced studies at molecular level could lead us to an alternative for envenoming of Pakistani Echis carinatus venom.

A Clot Twist: Extreme Variation in Coagulotoxicity Mechanisms in Mexican Neotropical Rattlesnake Venoms

Rattlesnakes are a diverse clade of pit vipers (snake family Viperidae, subfamily Crotalinae) that consists of numerous medically significant species. We used validated in vitro assays measuring venom-induced clotting time and strength of any clots formed in human plasma and fibrinogen to assess the coagulotoxic activity of the four medically relevant Mexican rattlesnake species Crotalus culminatus, C. mictlantecuhtli, C. molossus, and C. tzabcan. We report the first evidence of true procoagulant activity by Neotropical rattlesnake venom in Crotalus culminatus. This species presented a strong ontogenetic coagulotoxicity dichotomy: neonates were strongly procoagulant via Factor X activation, whereas adults were pseudo-procoagulant in that they converted fibrinogen into weak, unstable fibrin clots that rapidly broke down, thereby likely contributing to net anticoagulation through fibrinogen depletion. The other species did not activate clotting factors or display an ontogenetic dichotomy, but depleted fibrinogen levels by cleaving fibrinogen either in a destructive (non-clotting) manner or via a pseudo-procoagulant mechanism. We also assessed the neutralization of these venoms by available antivenom and enzyme-inhibitors to provide knowledge for the design of evidence-based treatment strategies for envenomated patients. One of the most frequently used Mexican antivenoms (Bioclon Antivipmyn®) failed to neutralize the potent procoagulant toxic action of neonate C. culminatus venom, highlighting limitations in snakebite treatment for this species. However, the metalloprotease inhibitor Prinomastat substantially thwarted the procoagulant venom activity, while 2,3-dimercapto-1-propanesulfonic acid (DMPS) was much less effective. These results confirm that venom-induced Factor X activation (a procoagulant action) is driven by metalloproteases, while also suggesting Prinomastat as a more promising potential adjunct treatment than DMPS for this species (with the caveat that in vivo studies are necessary to confirm this potential clinical use). Conversely, the serine protease inhibitor 4-(2-aminoethyl)benzenesulfonyl fluoride hydrochloride (AEBSF) inhibited the direct fibrinogen cleaving actions of C. mictlantecuhtli venom, thereby revealing that the pseudo-procoagulant action is driven by kallikrein-type serine proteases. Thus, this differential ontogenetic variation in coagulotoxicity patterns poses intriguing questions. Our results underscore the need for further research into Mexican rattlesnake venom activity, and also highlights potential limitations of current antivenom treatments.

A painful journey to antivenom: The therapeutic itinerary of snakebite patients in the Brazilian Amazon (The QUALISnake Study)

Access to antivenoms is not guarranteed for vulnerable populations that inhabit remote areas in the Amazon. The study of therapeutic itineraries (TI) for treatment of snakebites would support strategies to provide timely access to users. A TI is the set of processes by which individuals adhere to certain forms of treatment, and includes the path traveled in the search for healthcare, and practices to solve their health problems. This study aims to describe TIs of snakebite patients in the Brazilian Amazon. This study was carried out at the Fundação de Medicina Tropical Doutor Heitor Vieira Dourado, in Manaus, state of Amazonas, Brazil. The itinerary from the moment of the bite to the patient's admission to the reference unit was analyzed. Sample size was defined by saturation. After an exploratory survey to collect epidemiological variables, in-depth interviews were conducted following a semi-structured guide. Patients originated from rural areas of 11 different municipalities, including ones located >500 kilometers from Manaus. A great fragmentation was observed in the itineraries, marked by several changes of means of transport along the route. Four themes emerged from the analysis: exposure to snakebite during day-to-day activities, use of traditional therapeutic practices, and personal perception of the severity, as well as the route taken and its contingencies. Access to healthcare requires considerable effort on the part of snakebite patients. Major barriers were identified, such as the low number of hospitals that offer antivenom treatment, poor access to healthcare due to long distances and geographic barriers, low acceptability of healthcare offered in countryside, lack of use of personal protective equipment, common use of ineffective or deleterious self-care practices, late recognition of serious clinical signs and resistance to seeking medical assistance. Health education, promotion of immediate transport to health centers and decentralization of antivenom from reference hospitals to community healthcare centers in the Brazilian Amazon are more effective strategies that would to maximize access to antivenom treatment.

Schistocyte quantitation, thrombotic microangiopathy and acute kidney injury in Australian snakebite coagulopathy [ASP28]

INTRODUCTION

The major systemic manifestation of hemotoxicity in human snakebite envenoming is venom-induced consumption coagulopathy (VICC). A subset of patients with VICC develop thrombotic microangiopathy (TMA), in which acute kidney injury (AKI) occurs. We aimed to investigate the association between schistocytosis in snakebite patients with VICC and AKI, compared to non-envenomed patients.

METHODS

Serial blood films collected from a prospective cohort of snakebite patients (Australian Snakebite Project) were examined. Cases were classified a priori as non-envenomed snakebites (normal controls), envenomed without VICC, partial VICC without AKI, complete VICC without AKI, and VICC with AKI based on defined clinical and laboratory criteria. The percentage of schistocytes between groups was compared and correlated by Kendall's tau b test.

RESULTS

Seven hundred and eighty blood films from 234 snakebite cases were analyzed. There was a statistically significant correlation (τ = .69, SE .03, P < .001) for schistocytosis between the ordered groups of non-envenomed snakebites, envenomed without VICC, partial VICC without AKI, complete VICC without AKI, and VICC with AKI groups. Patients with VICC and AKI had a platelet nadir median of 42 × 10⁹ /L (interquartile range [IQR] :25-130 × 10⁹ /L), hemoglobin nadir of median 107 g/L (IQR 66-122 g/L), and maximum LDH median of 1128 U/L (IQR 474-3255 U/L). A 1.0% threshold for schistocytosis yielded 90% sensitivity (95% CI: 67%-98%) and 71% specificity (95% CI: 62%-79%) for predicting AKI in patients with VICC.

CONCLUSION

Schistocyte quantitation has good diagnostic utility in snakebite patients with VICC. A definition of snakebite TMA as MAHA with ≥1.0% schistocytes and thrombocytopenia, would appear to be appropriate.

Current research into snake antivenoms, their mechanisms of action and applications

Snakebite is a major public health issue in the rural tropics. Antivenom is the only specific treatment currently available. We review the history, mechanism of action and current developments in snake antivenoms. In the late nineteenth century, snake antivenoms were first developed by raising hyperimmune serum in animals, such as horses, against snake venoms. Hyperimmune serum was then purified to produce whole immunoglobulin G (IgG) antivenoms. IgG was then fractionated to produce F(ab) and F(ab')2 antivenoms to reduce adverse reactions and increase efficacy. Current commercial antivenoms are polyclonal mixtures of antibodies or their fractions raised against all toxin antigens in a venom(s), irrespective of clinical importance. Over the last few decades there have been small incremental improvements in antivenoms, to make them safer and more effective. A number of recent developments in biotechnology and toxinology have contributed to this. Proteomics and transcriptomics have been applied to venom toxin composition (venomics), improving our understanding of medically important toxins. In addition, it has become possible to identify toxins that contain epitopes recognized by antivenom molecules (antivenomics). Integration of the toxinological profile of a venom and its composition to identify medically relevant toxins improved this. Furthermore, camelid, humanized and fully human monoclonal antibodies and their fractions, as well as enzyme inhibitors have been experimentally developed against venom toxins. Translation of such technology into commercial antivenoms requires overcoming the high costs, limited knowledge of venom and antivenom pharmacology, and lack of reliable animal models. Addressing such should be the focus of antivenom research.

Vipers of Major clinical relevance in Europe: Taxonomy, venom composition, toxicology and clinical management of human bites

Snakebites in Europe are mostly due to bites from Viperidae species of the genus Vipera. This represents a neglected public health hazard with poorly defined incidence, morbidity and mortality. In Europe, fourteen species of "true vipers" (subfamily Viperinae) are present, eleven of which belong to the genus Vipera. Amongst these, the main medically relevant species due to their greater diffusion across Europe and the highest number of registered snakebites are six, namely: Vipera ammodytes, V. aspis, V. berus, V. latastei, V. seoanei and V. ursinii. Generally speaking, viper venom composition is characterised by many different toxin families, like phospholipases A2, snake venom serine proteases, snake venom metalloproteases, cysteine-rich secretory proteins, C-type lectins, disintegrins, haemorrhagic factors and coagulation inhibitors. A suspected snakebite is often associated with severe pain, erythema, oedema and, subsequently, the onset of an ecchymotic area around one or two visible fang marks. In the field, the affected limb should be immobilised and mildly compressed with a bandage, which can then be removed once the patient is being treated in hospital. The clinician should advise the patient to remain calm to reduce blood circulation and, therefore, decrease the spread of the toxins. In the case of pain, an analgesic therapy can be administered, the affected area can be treated with hydrogen peroxide or clean water. However, anti-inflammatory drugs and disinfection with alcohol or alcoholic substances should be avoided. For each patient, clinical chemistry and ECG are always a pre-requisite as well as the evaluation of the tetanus immunisation status and for which immunisation may be provided if needed. The treatment of any clinical complication, due to the envenomation, does not differ from treatments of emergency nature. Antivenom is recommended when signs of systemic envenomation exist or in case of advanced local or systemic progressive symptoms. Recommendations for future work concludes. The aim of this review is to support clinicians for the clinical management of viper envenomation, through taxonomic keys for main species identification, description of venom composition and mode of action of known toxins and provide a standardised clinical protocol and antivenom administration.

Novel transdisciplinary methodology for cross-sectional analysis of snakebite epidemiology at national scale

Background

Worldwide, it is estimated that snakes bite 4.5–5.4 million people annually, 2.7 million of which are envenomed, and 81,000–138,000 die. The World Health Organization reported these estimates and recognized the scarcity of large-scale, community-based, epidemiological data. In this context, we developed the “Snake-Byte” project that aims at (i) quantifying and mapping the impact of snakebite on human and animal health, and on livelihoods, (ii) developing predictive models for medical, ecological and economic indicators, and (iii) analyzing geographic accessibility to healthcare. This paper exclusively describes the methodology we developed to collect large-scale primary data on snakebite in humans and animals in two hyper-endemic countries, Cameroon and Nepal.

Methodology/Principal findings

We compared available methods on snakebite epidemiology and on multi-cluster survey development. Then, in line with those findings, we developed an original study methodology based on a multi-cluster random survey, enhanced by geospatial, One Health, and health economics components. Using a minimum hypothesized snakebite national incidence of 100/100,000/year and optimizing design effect, confidence level, and non-response margin, we calculated a sample of 61,000 people per country. This represented 11,700 households in Cameroon and 13,800 in Nepal. The random selection with probability proportional to size generated 250 clusters from all Cameroonian regions and all Nepalese Terai districts. Our household selection methodology combined spatial randomization and selection via high-resolution satellite images. After ethical approval in Switerland (CCER), Nepal (BPKIHS), and Cameroon (CNERSH), and informed written consent, our e-questionnaires included geolocated baseline demographic and socio-economic characteristics, snakebite clinical features and outcomes, healthcare expenditure, animal ownership, animal outcomes, snake identification, and service accessibility.

Conclusions/Significance

This novel transdisciplinary survey methodology was subsequently used to collect countrywide snakebite envenoming data in Nepal and Cameroon. District-level incidence data should help health authorities to channel antivenom and healthcare allocation. This methodology, or parts thereof, could be easily adapted to other countries and to other Neglected Tropical Diseases.

Snakebite envenoming was recently classified as a priority neglected tropical disease by the World Health Organization. Up to five million people are bitten, more than a million envenomed, and around 100,000 victims die, mainly in rural and remote areas of low- and middle-income countries. Snakebite envenoming not only affects victims acutely, but it can also cause long-term disability, disfiguring scars, and heavy economic burden due to treatment costs and inability to work. Previous studies have analyzed snakebite clinical, epidemiological, or socio-economic impacts independently, and little has been done to assess the impact of snakebite in animals and on the livelihoods of the communities that depend upon them.

We present an innovative, holistic, national-scale methodology that includes epidemiology, One Health, economic, and geographic information science approaches into one multi-cluster household survey. We randomly selected 250 sub-district areas from all Cameroonian regions and all Nepali Terai districts, which represented more than 61,000 participants in each country. This methodology could be adapted and implemented in other countries affected by snakebite.

Vulnerable areas to accidents with scorpions in Brazil

OBJECTIVE

To identify areas that present a higher risk of exposure to accidents with scorpions in Brazil.

METHODS

We used techniques of spatial prioritisation to determine the most vulnerable localities to envenomation by four scorpion species. Our prioritisation integrated ecological niche models with health investment, antivenin availability, access to health care facilities and metrics of human impact data.

RESULTS

The ecological niche models indicated that three scorpion species (Tityus bahiensis, Tityus serrulatus, and Tityus stigmurus) are more associated with human population density, while T. obscurus demonstrated a strong association with temperature variations during the year. Spatial prioritisation indicated that the areas with higher risk exposure to accidents with scorpions are in northern and northeastern Brazil. Alternatively, more isolated but densely populated areas in the southeastern and central regions also emerged as a priority.

CONCLUSION

Mapping areas where humans are more likely to interact with scorpions can assist in the design of efficient public health policies.

When snakebites complicate: a paediatric case with shock and compartment syndrome

We report the case of an 11-year-old boy brought to our emergency department 2 hours after a viper bite to his right hand. He suffered severe pain and rapidly progressive swelling with signs of haemodynamic compromise in keeping with distributive shock. The oedema progressed from his right wrist upwards to his forearm and upper arm with compartment syndrome ultimately resulting. He underwent fasciotomy of the right upper limb and antivenom serum was given. The patient required vasopressors for 48 hours and a total of nine surgical interventions were necessary. In the event of a snakebite, it is essential to promptly recognise the signs of severity, complications and indications for the administration of antivenom serum. We intend to highlight this rare shock aetiology and the need for emergency management if severe clinical signs are present. Early administration of antivenom serum is essential and it should be available in all emergency departments.

Snakebite Envenomation in Rwanda: Patient Demographics, Medical Care, and Antivenom Availability in the Formal Healthcare Sector

Snakebite envenomation (SBE) is a neglected One Health issue that overwhelmingly affects people living in rural and impoverished regions of Africa and Asia. Information on SBE is scarce in Rwanda; thus, our objectives were to 1) describe the demographics of SBE patients seeking hospital care, 2) evaluate physician adherence to national treatment guidelines, and 3) assess availability of snake antivenom at hospitals in Rwanda. To achieve these goals, we obtained national data on animal bites/stings and visited every district and provincial hospital in Rwanda to obtain physical records of SBE patients treated in 2017 and 2018. Hospital pharmacies were assessed for antivenom availability. We identified snakes as the second leading cause of animal bites, after dogs, among patients who sought hospital care in 2017 and 2018. Of 363 SBE patients, the highest number of cases occurred among children (< 18 years; 32%) and young adults (18-30 years; 33%), females (61%), farmers (82%), and those living in Eastern Province (37%). Overall, physician adherence to treatment guidelines was 63%. Prescriptions of vitamin K and antivenom were low (4% and 13%, respectively), and only 8% of hospital pharmacies had antivenom in stock throughout the study period. The antivenom stocked was an Indian generic suited for Asian snakes. This minimum estimate of hospitalization cases does not include individuals who died in communities or sought care outside the formal sector. Our study highlights the need to map incidence, risk factors, and patient experiences to mitigate human-snake conflicts and improve patient outcomes.

Antivenomics and in vivo preclinical efficacy of six Latin American antivenoms towards south-western Colombian Bothrops asper lineage venoms

Background

Bothrops asper represents the clinically most important snake species in Central America and Northern South America, where it is responsible for an estimated 50–80% of snakebites. Compositional variability among the venom proteomes of B. asper lineages across its wide range mirrors clinical differences in their envenomings. Bothropic antivenoms generated in a number of Latin American countries commonly exhibit a certain degree of paraspecific effectiveness in the neutralization of congeneric venoms. Defining the phylogeographic boundaries of an antivenom's effectivity has implications for optimizing its clinical use. However, the molecular bases and impact of venom compositions on the immune recognition and neutralization of the toxic activities of across geographically disparate populations of B. asper lineages has not been comprehensively studied.

Methodology/Principal findings

Third-generation antivenomics was applied to quantify the cross-immunorecognizing capacity against the individual components of venoms of three B. asper lineages (B. asper (sensu stricto), B. ayerbei and B. rhombeatus) distributed in south-western (SW) Colombia, of six Latin American antivenoms, produced against homologous (Colombia, INS-COL and PROBIOL) and Costa Rica (ICP)), and heterologous (Argentina (BIOL), Perú (INS-PERU) and Venezuela (UCV)) bothropic venoms. In vivo neutralization assays of the lethal, hemorrhagic, coagulant, defibrinogenating, myotoxic, edematogenic, indirect hemolytic, and proteolytic activities of the three SW Colombian B. asper lineage venoms were carried to compare the preclinical efficacy of three (Colombian INS-COL and PROBIOL, and Costa Rican ICP) antivenoms frequently used in Colombia. Antivenomics showed that all the six antivenom affinity matrices efficiently immunoretained most of the B. asper lineages venom proteins and exhibited impaired binding towards the venoms' peptidomes. The neutralization profile of the INS-COL, PROBIOL and ICP antivenoms towards the biological activities of the venoms of SW Colombian B. asper (sensu stricto), B. ayerbei and B. rhombeatus lineages was coherent with the antivenomics outcome. In addition, the combination of in vitro (antivenomics) and in vivo neutralization results allowed us to determine their toxin-specific and venom neutralizing antibody content. Noteworthy, heterologous INS-PERU, BIOL, and UCV bothropic antivenoms had equal or higher binding capacity towards the venoms components of SW Colombian B. asper lineages that the homologous Colombian and Costa Rican antivenoms.

Conclusions/Significance

The combined in vitro and in vivo preclinical outcome showed that antivenoms manufactured in Colombia and Costa Rica effectively neutralize the major toxic activities of SW Colombian B. asper lineage venoms. The antivenomics profiles of the heterologous antivenoms manufactured in Argentina, Venezuela, and Perú strongly suggests their (pre)clinical adequacy for the treatment of B. asper lineage envenomings in SW Colombia. However, their recommendation in the clinical setting is pending on in vivo neutralization testing and clinical testing in humans. Bothrops asper is a highly adaptable snake species complex, which is considered the most dangerous snake throughout much of its distribution range from the Atlantic lowland of eastern México to northwestern Perú. Antivenoms are the only scientifically validated treatment of snakebite envenomings. Venom variation is particularly common in wide ranging species, such as B. asper, and may result in variable clinical presentations of envenomings, as is the case for the B. asper species complex, potentially undermining the efficacy of snakebite treatments depending on the immunization mixture used in the generation of the antivenom. Conversely, phylogenetic conservation of antigenic determinants confers an unpredictable degree of paraspecificity to homologous antivenoms produced for a geographic area, but also to heterologous congeneric antivenoms, towards the venom components of allopatric conspecific populations. This work aimed at comparing the preclinical profile of a panel of Latin American homologous and heterologous antivenoms against the venoms of B. asper lineages distributed in SW Colombia. The outcome of this study strongly suggests the suitability of considering the heterologous antivenoms BIOL (Argentina), UCV (Venezuela) and INS-PERU (Perú) as alternatives to homologous Colombian INS-COL and PROBIOL and Costa Rican ICP antivenoms for the treatment of envenomings by B. asper (sensu stricto) in W Colombia and Ecuador, B. ayerbei in Cauca and Nariño (Colombia), and B. rhombeatus in Cauca river valley, SW Colombia.

Snakebite envenoming is an important occupational health problem, particularly in rural areas of developing countries. The timely administration of an effective antivenom remains the mainstay of snakebite management. However, the use of antivenoms is often limited by non-availability due to high cost or by lack of effectiveness. Antivenom shortage can be addressed through the generation of novel polyspecific antivenoms of wide clinical efficacy against the venoms of the medically-relevant snake species within the geographical range where these antivenoms are intended to be deployed, but also by optimizing the paraspecific use of current antivenoms. In Colombia, antivenoms are supplied by two manufacturers, one public, the Instituto Nacional de Salud (INS), and one private, Laboratorios Probiol (PROBIOL). However, the antivenom supply in Colombia has traditionally been insufficient, a circumstance that has led the Colombian Ministerio de Salud y Protección Social to issue several resolutions and decrees to announce this health emergency in the country, and to import antivenoms produced in México and Costa Rica. Contrary to these countries, where B. asper represents the only species of the genus, in SW Colombia three close phylogenetically related B. asper lineages, B. asper (sensu stricto), B. rhombeatus, and B. ayerbei, are responsible for most severe cases of snakebite accidents and exhibit remarkable differences in the physiopathological profile of their envenomings. This work aimed to assess the immunorecognition characteristics of a panel of antivenoms manufactured in Colombia, Costa Rica, Argentina, Perú and Venezuela towards the venoms of the three SW Colombian B. asper lineages. Additionally, combined quantitative in vitro and in vivo data show that the homologous antivenoms produced in Colombia (INS-COL, PROBIOL) and Costa Rica (ICP) effectively neutralize the lethality and the major toxic activities tested of the three SW Colombian B. asper lineage venoms. Heterologous Argentinian (BIOL), Venezuelan (UCV) and Peruvian (INS-PERU) antivenoms also showed comparable, even higher, effective immunocapturing ability towards the venom proteomes of SW Colombian B. asper (sensu stricto), B. rhombeatus, and B. ayerbei, than the Colombian and Costa Rican antivenoms. These results are in line with previous studies highlighting the notable conservation of paraspecific antigenic determinants across the phylogeny of genus Bothrops, and advocate for considering the heterologous Argentinian, Venezuelan and Peruvian antivenoms as further therapeutic alternatives for the treatment of B. asper spp. snakebites in Colombia.

Overview of snakebite in Brazil: Possible drivers and a tool for risk mapping

Snakebite envenoming affects close to 2.7 million people globally every year. In Brazil, snakebites are reported to the Ministry of Health surveillance system and cases receive antivenom free of charge. There is an urgent need to identify higher risk areas for antivenom distribution, and to develop prevention activities. The objective of this study is to provide an overview of the epidemiological situation of snakebite envenoming in Brazil and explore possible drivers; as well as to create a flowchart tool to support decision-makers identify higher risk areas. An ecological-type study was carried out using data by municipality (2013–2017). Study parts: 1) Create a geocoded database and perform a descriptive and cluster analysis; 2) Statistical analysis to measure the association of snakebite and possible environmental and socioeconomic drivers; 3) Develop a flowchart to support decision-makers and the application of this tool in one state (Rio Grande do Sul) as an example. An average of 27,120 snakebite cases per year were reported at the country level. Clusters of municipalities with high numbers of snakebites are mostly found in the Amazon Legal Region. The negative binomial regression model showed association with the snakebite case count: the type of major habitat, tropical or non-tropical; temperature; percentage of urbanization; precipitation; elevation; GDP per capita; a weaker relation with forest loss; and with venomous snake richness. The state where the instrument was applied reported 4,227 snakebites in the period. Most municipalities were considered as medium risk and 56/496 as high risk according to the tool created. Snakebite cases are distributed across the entire country with the highest concentration in the Legal Amazon Region. This creates a complex situation both for better understanding of the association of environmental and socioeconomic factors with snakebites and for the distribution and maintenance of antivenom to remote areas. Research into types of antivenom with a longer shelf life without the need for refrigeration is needed.

It is estimated that snakebite envenoming affects around 2.7 million people every year worldwide. In Brazil, snakebite is part of the Ministry of Health surveillance system and cases receive antivenom free of charge. With a vast territory and limited production of antivenom, there is need to identify higher risk areas for its distribution and to develop preventative actions. The objective of this study is to provide an overview of the epidemiological situation of snakebite envenoming in Brazil and explore possible environmental and socioeconomic factors related to snakebites. On the basis of this information, a flowchart tool to support decision-makers identify higher risk areas was created and applied in one state as an example. An average of 27,120 snakebite cases per year were reported in Brazil, with the highest number of cases and rates in the Legal Amazon Region. The multivariable statistics analysis showed association of snakebite with environmental factors (type of major habitat, tropical or non-tropical; temperature; precipitation; elevation) and socioeconomic (lower percentage of urbanization; lower GDP per capita); also, a weaker relation with forest loss, and with venomous snake richness. The tool created to support decision-makers was applied in the state of Rio Grande do Sul, with 4,227 reported snakebites during the period. According to this tool, the majority of municipalities in this state were considered as medium risk and 56/496 as high risk. Snakebite cases are distributed across the entire country; however, the highest concentration is in the Legal Amazon Region. This creates a complex situation both for better understanding of the association of environmental and socioeconomic factors with snakebites and for the distribution and maintenance of antivenom to remote areas.

Assessment of neutralization of Micrurus venoms with a blend of anti-Micrurus tener and anti-ScNtx antibodies

BACKGROUND

Micrurus venoms contain two main groups of toxic protein components: short-chain α-neurotoxins (SNtx) and phospholipases type A₂ (PLA₂). In North America, generally, the Micrurus venoms have low abundance of SNtx compared to that of PLA₂s; however, both are highly toxic to mammals, and consequently both can play a major role in the envenomation processes. Concerning the commercial horse-derived antivenoms against Micrurus from the North America region, they contain a relatively large amount of antibodies against PLA₂s, and a low content of antibodies against short chain α-neurotoxins. This is mainly due to the lower relative abundance of SNtxs, and also to its poor immunogenicity due to their size and nature. Hence, Micrurus antivenoms made in North America usually present low neutralizing capacity towards Micrurus venoms whose lethality depend largely on short chain α-neurotoxins, such as South American Micrurus species.

METHODS

Horses were hyperimmunized with either the venom of M. tener (PLA₂-predominant) or a recombinant short-chain consensus α-neurotoxin (ScNtx). Then, the combination of the two monospecific horse antibodies (anti-M. tener and anti-ScNtx) was used to test their efficacy against eleven Micrurus venoms.

RESULTS

The blend of anti-M. tener and anti-ScNtx antibodies had a better capacity to neutralize the lethality of diverse species from North, Central and South American Micrurus venoms. The antibodies combination neutralized both the ScNtx and ten out of eleven Micrurus venom tested, and particularly, it neutralized the venoms of M. distans and M. laticollaris that were neither neutralized by monospecific anti-M. tener nor anti-ScNtx.

CONCLUSIONS

These results provide a proof-of-principle for using recombinant immunogens to enrich poor or even non-neutralizing antisera against elapid venoms containing short chain α-neurotoxins to develop antivenoms with higher effectiveness and broader neutralizing capacity.

Crowdsourcing snake identification with online communities of professional herpetologists and avocational snake enthusiasts

Species identification can be challenging for biologists, healthcare practitioners and members of the general public. Snakes are no exception, and the potential medical consequences of venomous snake misidentification can be significant. Here, we collected data on identification of 100 snake species by building a week-long online citizen science challenge which attracted more than 1000 participants from around the world. We show that a large community including both professional herpetologists and skilled avocational snake enthusiasts with the potential to quickly (less than 2 min) and accurately (69-90%; see text) identify snakes is active online around the clock, but that only a small fraction of community members are proficient at identifying snakes to the species level, even when provided with the snake's geographical origin. Nevertheless, participants showed great enthusiasm and engagement, and our study provides evidence that innovative citizen science/crowdsourcing approaches can play significant roles in training and building capacity. Although identification by an expert familiar with the local snake fauna will always be the gold standard, we suggest that healthcare workers, clinicians, epidemiologists and other parties interested in snakebite could become more connected to these communities, and that professional herpetologists and skilled avocational snake enthusiasts could organize ways to help connect medical professionals to crowdsourcing platforms. Involving skilled avocational snake enthusiasts in decision making could build the capacity of healthcare workers to identify snakes more quickly, specifically and accurately, and ultimately improve snakebite treatment data and outcomes.

Prevalence, vulnerability and epidemiological characteristics of snakebite in agricultural settings in rural Sri Lanka: A population-based study from South Asia

Background

The burden of snakebite remains poorly characterised because of the paucity of population-based data. Further, factors determining the vulnerability of individuals within rural communities to snakebite have been rarely investigated. We undertook a population-based study to determine the prevalence, vulnerability and epidemiological characteristics of snakebite in rural Sri Lanka.

Methods and findings

A population-based cross-sectional study was conducted among 8707 current residents in the district of Ampara, representing typical rural Sri Lanka. The sample was recruited using multi-stage cluster sampling with probability proportionate-to-size. Snakebite victims were identified using the WHO criteria. Data were collected using a pre-tested interviewer-administered questionnaire.

Each household had on average 3.8 persons; mean age 28.3 years (SD = 18.2); 51.3% males. The one-year point prevalence of snakebites was 17.6 per 1000 residents (95% CI: 15–20.6) and 6.12 per 100 households (95% CI: 5.25–7.13), while the lifetime prevalence was 9.4 per 100 residents (95% CI: 8.8–10.0) and 30.5 per 100 households (95% CI: 28.6–32.2) with a case fatality ratio of 0.033. Venomous snakebites accounted for 28.1%; snakes were unidentified among 30.1%. Compared to the non-snakebite victims, being single, males, of Sinhala ethnicity, aged >19 years, low education and socioeconomic status, engaging in farming or unskilled outdoor occupations denoted vulnerability to snakebites. Outdoor bites (77.8%) were more common among males; during daytime; mostly while walking; within the rural terrains and home gardens; on lower limbs; mostly by hump-nosed and Russell viper. Indoor bites were more common among females; during night-time; while sleeping and barefooted; on lower limbs; mostly by hump-nosed vipers, kraits and non-venomous snakes.

Conclusions

The burden of snakebite is considerably high among rural populations. The concept of vulnerability can be useful in healthcare decision-making and resource allocation.