Estimating economic and disease burden of snakebite in ASEAN countries using a decision analytic model

A fatal snakebite envenomation due to King cobra (Ophiophagus hannah) in the Eastern Visayas, Philippines

This report details a documented case of fatal King cobra (Ophiophagus hannah) envenomation in the Philippines. A 46-year-old woman from a mountainous town in Leyte was bitten on her left thigh by a snake. Despite receiving prompt medical attention, including administration of fluids and oxygen, she went into arrest and succumbed within 2.5 hours of the bite. Inadequate pre-hospital care, including endotracheal intubation and assisted ventilation, highlights a notable gap in emergency medical services. Photographic evidence, verified by a herpetologist, confirmed the involvement of a King cobra, with venom presenting with a swift and lethal systemic effect that led to the patient's demise, despite minimal local manifestations. This incident accentuates the urgent need for accessible, effective antivenom and improved snakebite management protocols in the Philippines. It also calls for heightened awareness and preparedness among pre-hospital healthcare providers and the public, alongside advocating for more research into snakebite envenomation.

Lack of controlled studies on snakebite prevention: a rapid review

Globally, snakebites cause an estimated 80 000-140 000 deaths annually. While there are evidence-based recommendations for managing snakebite victims, recommendations on the prevention of snakebites are limited to expert opinions. We conducted a rapid review to summarise evidence from human studies with a control group on preventing snakebites. Searching PubMed, Web of Science, Scopus, CINAHL and EMBASE with inclusive search terms without language or time limits only yielded three eligible studies (one case control study and two prospective controlled clinical studies), highlighting a knowledge gap. Two studies in Nepal by the same group showed that health education of stakeholders and sleeping under a bednet can significantly reduce snakebite incidence (p<0.05), but these observations are not confirmed elsewhere, and because of the high risk of bias the certainty of evidence was low. The third study from Sri Lanka, which assessed if sleeping above ground would prevent snakebites, had inconclusive results. This demonstrates an urgent need for studies with a control group to guide evidence-based recommendations for snakebite prevention. Potential interventions tested can range from low-cost measures such as wearing appropriate footwear in resource-limited settings to testing the efficacy of chemical, biological (e.g. rodent control) or device-based methods and community-supported platforms tracking snakebite sightings with real-time geolocation data in highly resourced settings.

Cost-effectiveness of add-on empagliflozin versus standard of care in management of CKD in Malaysia, Thailand and Vietnam - findings from a modelling study assessing an EMPA-KIDNEY eligible population, using CKD progression model

BACKGROUND AND OBJECTIVES

Nearly one in ten individuals in South-East Asia are estimated to be affected by chronic kidney disease (CKD). The burden of end-stage kidney disease is significant and can be heavy on the healthcare system. The recent EMPA-KIDNEY trial demonstrated a significant reduction in the risk of kidney disease progression or cardiovascular death in patients with CKD with a broad range of kidney function using add-on empagliflozin versus standard of care (SoC) alone. The objective of this study was to estimate the economic benefit of empagliflozin for patients with CKD in Malaysia, Thailand and Vietnam.

METHODS

An individual patient level simulation model with an annual cycle that estimates the progression of kidney function and associated risk-factors was employed. Local costs and mortality rates were estimated from a wide range of published literature. A healthcare perspective was used over a 50-year time horizon.

RESULTS

The use of add-on empagliflozin versus SoC alone was found to be cost-saving in Malaysia and Thailand and cost-effective (ICER: 77,838,407 Vietnam Dong/QALY vs. a willingness to pay threshold of 96,890,026/QALY) in Vietnam. The bulk of the costs avoided over a lifetime is derived from the prevention or delay of dialysis initiation or kidney transplant - the cost offsets were nearly twice the additional treatment cost. The results were similar in patients with and without diabetes and across broad range of albuminuria.

CONCLUSIONS

The use of add-on empagliflozin in a broad population of patients with CKD is expected to be cost-saving in Malaysia and Thailand and cost-effective in Vietnam and will help alleviate the increasing burden of CKD in the region.

Inhibition of bacterial biofilms by the snake venom proteome

Snake venoms possess a range of pharmacological and toxicological activities. Here we evaluated the antibacterial and anti-biofilm activity against methicillin-susceptible and methicillin-resistant Staphylococcus aureus (MSSA and MRSA) of venoms from the Samar spitting cobra Naja samarensis and the Puff adder Bitis arietans. Both venoms prevented biofilm production by pathogenic S. aureus in a growth-independent manner, with the B. arietans venom being most potent. Fractionation showed the active molecule to be heat-labile and >10 kDa in size. Proteomic profiles of N. samarensis venom revealed neurotoxins and cytotoxins, as well as an abundance of serine proteases and three-finger toxins, while serine proteases, metalloproteinases and C-lectin types were abundant in B. arietans venom. These enzymes may have evolved to prevent bacteria colonising the snake venom gland. From a biomedical biotechnology perspective, they have valuable potential for anti-virulence therapy to fight antibiotic resistant microbes.

Frequency, geographical distribution and outcomes of pit viper bites in Malaysia consulted to Remote Envenomation Consultancy Services (RECS) from 2017 to 2020

Not all pit viper species are present in every state of Malaysia and their distribution varies according to altitude. There is limited information on pit viper bite incidence and its geographical distribution. This was a cross-sectional study of confirmed pit viper bite cases referred to Remote Envenomation Consultancy Services (RECS) from January 2017 to December 2020. Data was collected following the approval of institutional research ethics committee. Universal sampling methods were used. Confirmed pit viper bite cases in each state, geographical location and the antivenom used were reported. A total of 523 confirmed pit viper bite injuries occurred over the 4-year study period. The majority were Malaysians, male and young adults. Most were non-occupational related (83.9%) and involved the upper limbs (46.8%). The commonest pit viper species involved was Trimeresurus purpureomaculatus (23.7%). Green pit viper antivenom (GPAV) was the most frequent antivenom used (n = 51) with the majority of patients requiring only one dose (3 vials). This study provides a better appreciation of indigenous pit viper species distribution for each state and reflects the requirement of appropriate antivenom to be stocked in each state or district hospital.

Antivenom preclinical efficacy testing against Asian snakes and their availability in Asia: A systematic review

BACKGROUND

Cross-neutralizing strategy has been applied to improve access to antivenoms, a key to reducing mortality and disability of snakebite envenoming. However, preclinical studies have been conducted to identify antivenoms' cross-neutralizing ability when clinical studies may not be considered ethical. Therefore, this study aimed to identify and summarize scattered evidence regarding the preclinical efficacy of antivenoms against Asian snakes.

METHODOLOGY/PRINCIPLE FINDINGS

In this systematic review, we searched for articles published until May 30, 2022, in PubMed, Scopus, Web of Science, and Embase. Preclinical studies that reported the available antivenoms' neutralizing ability against Asian snake lethality were included. Quality assessment was performed using the Systematic Review Centre for Laboratory animal Experimentation's risk of bias tool and the adapted the Animal Research Reporting In Vivo Experiments guidelines. The availability of effective antivenoms against Asian snakes was analyzed by comparing data from included studies with snakebite-information and data platforms developed by the World Health Organization. Fifty-two studies were included. Most studies assessed the antivenom efficacy against snakes from Southeast Asia (58%), followed by South Asia (35%) and East Asia (19%). Twenty-two (49%) medically important snakes had antivenom(s) with confirmed neutralizing ability. Situation analyses of the availability of effective antivenoms in Asia demonstrated that locally produced antivenoms did not cover all medically important snakes in each country. Among countries without local antivenom production, preclinical studies were conducted only in Bangladesh, Sri Lanka, and Malaysia. Risk of bias assessment was limited in some domains because of unreported data.

CONCLUSIONS/SIGNIFICANCE

Cross-neutralizing of antivenoms against some medically important snakes in Asia was confirmed. This strategy may improve access to geographically effective antivenoms and bypass investment in novel antivenom development, especially in countries without local antivenom production. A database should be developed to aid the development of a snakebite-information system.

Clinical Profile and Pharmacological Management of Snakebites in Community Care Units: A Retrospective Study Using Two Military Hospital Databases in South Thailand

Snakebite envenoming is an occupational hazard in remote rural areas of South Thailand, where the highest incidence of snakebites is reported. In this work, a hospital-based retrospective study of snakebite patients from 2012 to 2022 at Fort Wachirawut Hospital and Fort Thepsatrisrisunthon Hospital, located in Nakhon Si Thammarat province, Thailand was conducted. Data from the laboratory investigation, physical examinations of snakebite victims, and clinical management, including pharmacological and non-pharmacological treatments, were evaluated. A total of 54 snakebite victims were included. The median age of patients was 49 years (IQR, 28 to 63). Males accounted for 74.1% of all participants. The majority of patients were bitten by Malayan pit vipers (68.5%), followed by unidentified snakes (18.5%), other non-venomous snakes (7.4%), and cobras (5.6%). The most common clinical manifestations were swelling (90.2%) and local pain (73.2%). One patient experienced respiratory failure following an envenoming by an unidentified venomous snake. No deaths were observed in this study. In total, 24 patients received antivenom administration (44.4%), most of whom were from Fort Wachirawut Hospital. Patients who were administered antivenom showed a median admission duration of three days (IQR, 3 to 4), compared with two days (IQR, one to three) for those who did not receive antivenom treatment (p < 0.001). In addition, paracetamol and prophylactic antibiotics, namely, amoxicillin-clavulanate and dicloxacillin, were the most common pharmacotherapies following snakebites. Overall, it was observed that these two community hospitals undertook appropriate clinical management under the standard guidelines for snakebite patients. This might be due to the effective emergency management, facilities, and clinical consultations. Finally, the management process in the medical teams also plays a crucial role in minimizing the severity of snakebite outcomes.

Medically important snakes and snakebite envenoming in Iran

Snakebite is a common health condition in Iran with a diverse snake fauna, especially in tropical southern and mountainous western areas of the country with plethora of snake species. The list of medically important snakes, circumstances and effects of their bite, and necessary medical care require critical appraisal and should be updated regularly. This study aims to review and map the distributions of medically important snake species of Iran, re-evaluate their taxonomy, review their venomics, describe the clinical effects of envenoming, and discuss medical management and treatment, including the use of antivenom. Nearly 350 published articles and 26 textbooks with information on venomous and mildly venomous snake species and snakebites of Iran, were reviewed, many in Persian (Farsi) language, making them relatively inaccessible to an international readership. This has resulted in a revised updated list of Iran's medically important snake species, with taxonomic revisions of some, compilation of their morphological features, remapping of their geographical distributions, and description of species-specific clinical effects of envenoming. Moreover, the antivenom manufactured in Iran is discussed, together with treatment protocols that have been developed for the hospital management of envenomed patients.

Venom-gland transcriptomics of the Malayan pit viper (Calloselasma rhodostoma) for identification, classification, and characterization of venom proteins

The Malayan pit viper (Calloselasma rhodostoma) is a hemotoxic snake widely found in Southeast Asia and is responsible for the majority of poisoning cases in this region, including Thailand. However, a comprehensive knowledge of the venom protein profile and classification, as well as novel venom proteins, of this viper is still limited. Recently, the detailed composition of several snake venoms has been discovered through the use of transcriptome analysis. Therefore, the aim of this study was to employ a next-generation sequencing platform and bioinformatics analysis to undertake venom-gland de novo transcriptomics of Malayan pit vipers. Furthermore, 21,272 functional coding genes were identified from 36,577 transcripts, of which 314 transcripts were identified as toxin proteins, accounting for 61.41% of total FPKM, which can be categorized into 22 toxin gene families. The most abundant are snake venom metalloproteinase kistomin (P0CB14) and zinc metalloproteinase/disintegrin (P30403), which account for 60.47% of total toxin FPKM and belong to the SVMP toxin family, followed by snake venom serine protease 1 (O13059) and Snaclec rhodocetin subunit beta (P81398), which account for 6.84% and 5.50% of total toxin FPKM and belong to the snake venom serine protease (SVSP) and Snaclec toxin family, respectively. Amino acid sequences of the aforementioned toxins were compared with those identified in other important medical hemotoxic snakes from Southeast Asia, including the Siamese Russell's viper (Daboia siamensis) and green pit viper (Trimeresurus albolabris), in order to analyze their protein homology. The results demonstrated that ranges of 58%-62%, 31%-60%, and 48%-59% identity was observed among the SVMP, Snaclec, and SVSP toxin families, respectively. Understanding the venom protein profile and classification is essential in interpreting clinical symptoms during human envenomation and developing potential therapeutic applications. Moreover, the variability of toxin families and amino acid sequences among related hemotoxic snakes found in this study suggests the use and development of universal antivenom for the treatment of envenomating patients is still challenging.

A case of fatal envenomation by a captive puff adder (Bitis arietans) in Malaysia

The Puff Adder (Bitis arietans) is a viper native to Africa and the Middle East. Envenomation by this species often requires the administration of appropriate antivenom in order to achieve a favorable outcome. A patient was bitten in both hands by a captive B. arietans presented to a teaching hospital in Malaysia. The patient developed painful progressive swelling on both limbs that extended to the chest, hypotension, hypokalemia with worsening anemia, thrombocytopenia, coagulopathy, and severe metabolic acidosis. The patient was managed supportively while waiting for the appropriate antivenom, Antivipmyn-Africa, from the Singapore Zoo. The patient developed cardiorespiratory arrest twice and did not recover from the second. The patient was pronounced dead 23 hours post-incident. The local unavailability of the appropriate antivenom may be the most important factor that contributed to the patient's death. There is also a need to amend the Malaysian Wildlife Act in order to prevent such cases from recurring.

A case series of samar cobra, Naja samarensis Peters, 1861 (Elapidae) envenomation

The Samar cobra, Naja samarensis Peters, 1861 is one of the World Health Organization's category I venomous snakes in the Philippines. Although N. samarensis is known to inhabit Eastern Visayas, unlike N. philippinensis in Luzon, no clinical case reports have yet been published in the international literature. No immuno-diagnostic assays have been developed for venomous snakes in the Philippines, even for research purposes. Therefore, identification of the causative snake in hospitals is challenging. In vivo pre-clinical tests using mice showed that locally-produced antivenom raised against N. philippinensis venom ["Purified Cobra Antivenom (PCAV)"] cross-neutralised N. samarensis venom. Here, we present five snakebite envenomation cases where causative snakes were confirmed in photos as N. samarensis by an expert local herpetologist. Patients' symptoms and signs varied, from mild to extensive local cytotoxic to systemic neurotoxic envenomation. In one case, venom had been spat into the eye. Out of five patients, two underwent surgical debridement of necrotic tissue at the bite site. One paediatric patient was intubated because of cardiopulmonary arrest. Except for the spitting cobra case, four cases were successfully treated with PCAV and supportive management. These are the first clinical case reports of confirmed N. samarensis envenomation.

An immunoinformatic approach to assessing the immunogenic capacity of alpha-neurotoxins in elapid snake venoms

Introduction: Most elapid snakes produce venoms that contain alpha-neurotoxins (α-NTXs), which are proteins that cause post-synaptic blockade and paralysis in snakebite envenoming. However, existing elapid antivenoms are known for their low potency in neutralizing the neurotoxic activity of α-NTXs, while the immunological basis has not been elucidated. Methods: In this study, a structure-based major histocompatibility complex II (MHCII) epitope predictor of horse (Equus caballus), complemented with DM-editing determinant screening algorithm was adopted to assess the immunogenicity of α-NTXs in the venoms of major Asiatic elapids (Naja kaouthia, Ophiophagus hannah, Laticauda colubrina, Hydrophis schistosus, Hydrophis curtus). Results: The scoring metric M₂R, representing the relative immunogenic performance of respective α-NTXs, showed all α-NTXs have an overall low M₂R of <0.3, and most of the predicted binders feature non-optimal P1 anchor residues. The M₂R scores correlate strongly (R² = 0.82) with the potency scores (p-score) generated based on the relative abundances of α-NTXs and the neutralization potency of commercial antivenoms. Discussion: The immunoinformatic analysis indicates that the inferior antigenicity of α-NTXs is not only due to their small molecular size but also the subpar immunogenicity affected by their amino acid composition. Structural modification with conjugation and synthetic epitope as immunogen may potentially enhance the immunogenicity for improved antivenom potency against α-NTXs of elapid snakes.

Potential economic and clinical implications of improving access to snake antivenom in five ASEAN countries: A cost-effectiveness analysis

Background

Despite domestic production of antivenoms in the Association of Southeast Asian Nations (ASEAN) countries, not all victims with snakebite envenomings indicated for antivenom received the appropriate or adequate effective dose of antivenom due to insufficient supply and inadequate access to antivenoms. We aimed to conduct a cost-effectiveness analysis to project the potential economic and clinical impact of improving access to antivenoms when all snakebite envenomings in ASEAN countries were hypothetically treated with geographically appropriate antivenoms.

Methodology

Using a decision analytic model with input parameters from published literature, local data, and expert opinion, we projected the impact of “full access” (100%) to antivenom, compared to “current access” in five most impacted ASEAN countries, including Indonesia (10%), Philippines (26%), Vietnam (37%), Lao PDR (4%), and Myanmar (64%), from a societal perspective with a lifetime time horizon. Sensitivity analyses were performed.

Principal findings

In base-case analyses, full access compared to current access to snake antivenom in the five countries resulted in a total of 9,362 deaths averted (-59%), 230,075 disability-adjusted life years (DALYs) averted (-59%), and cost savings of 1.3 billion USD (-53%). Incremental cost-effectiveness ratios (ICERs) of improving access to antivenom found higher outcomes but lower costs in all countries. Probabilistic sensitivity analyses of 1,000 iterations found that 98.1–100% of ICERs were cost-saving.

Conclusion/Significance

Improving access to snake antivenom will result in cost-saving for ASEAN countries. Our findings emphasized the importance of further strengthening regional cooperation, investment, and funding to improve the situation of snakebite victims in ASEAN countries.

In the Association of Southeast Asian Nations (ASEAN) countries, it was estimated that annually there were 242,648 snakebite victims in ASEAN of which 15,909 victims were dead. Despite domestic production of antivenoms in ASEAN countries, not all victims with snakebite envenomings indicated for antivenom received the appropriate or adequate effective dose of antivenom due to insufficient supply and inadequate access to antivenoms. Especially in Indonesia, Philippines, Vietnam, Lao PDR, and Myanmar, where 4–64% of victims who needed antivenoms were treated with antivenoms. We conducted a cost-effectiveness analysis to project the potential economic and clinical impact of improving access to antivenoms when all victims with snakebite envenomings in the five most impacted ASEAN countries were hypothetically treated with geographically appropriate antivenoms. Improving access to snake antivenom to the full level of access compared to the current level in the five ASEAN countries resulted in a total of 9,362 deaths averted (-59%), 230,075 disability-adjusted life years (DALYs) averted (-59%), and cost savings of 1.3 billion USD (-53%). Our study demonstrated improving access to snake antivenom from the current to the full level of access in ASEAN countries is a cost-saving strategy. Our findings emphasized the importance of further strengthening regional cooperation, investment, and funding to improve the situation of snakebite victims in ASEAN countries to reach the ultimate goal where all victims with snakebite envenoming needing antivenom adequately received the geographically appropriate antivenoms.