Clinical and laboratory features distinguishing between Deinagkistrodon acutus and Daboia siamensis envenomation

In vitro immunoreactivity and in vivo neutralization of Trimeresurus gracilis venom with antivenoms targeting four pit viper species

Snakebite envenomation is a significant global health issue that requires specific antivenom treatments. In Taiwan, available antivenoms target a variety of snakes, but none specifically target Trimeresurus gracilis, an endemic and protected species found in the high mountain areas of Taiwan. This study evaluated the effectiveness of existing antivenoms against T. gracilis venom, focusing on a bivalent antivenom developed for Trimeresurus stejnegeri and Protobothrops mucrosquamatus (TsPmAV), as well as monovalent antivenoms for Deinagkistrodon acutus (DaAV) and Gloydius brevicaudus (GbAV). Our research involved in vivo toxicity testing in mice and in vitro immunobinding experiments using (chaotropic) enzyme-linked immunosorbent assays, comparing venoms from four pit viper species (T. gracilis, T. stejnegeri, P. mucrosquamatus, and D. acutus) with three types of antivenoms. These findings indicate that TsPmAV partially neutralized T. gracilis venom, marginally surpassing the efficacy of DaAV. In vitro tests revealed that GbAV displayed higher binding capacities toward T. gracilis venom than TsPmAV or DaAV. Comparisons of electrophoretic profiles also reveal that T. gracilis venom has fewer snake venom C-type lectin like proteins than D. acutus, and has more P-I snake venom metalloproteases or fewer phospholipase A2 than G. brevicaudus, T. stejnegeri, or P. mucrosquamatus. This study highlights the need for antivenoms that specifically target T. gracilis, as current treatments using TsPmAV show limited effectiveness in neutralizing local effects in patients. These findings provide crucial insights into clinical treatment protocols and contribute to the understanding of the evolutionary adaptation of snake venom, aiding in the development of more effective antivenoms for human health.

Comparative analysis of Deinagkistrodon acutus venom from Taiwan and China utilizing chromatographic, electrophoretic, and bioinformatic approaches, along with ELISA employing a monospecific antivenom

Deinagkistrodon acutus is a medically important pitviper inhabiting mainly South China and Taiwan. The hemorrhagic effects of its envenoming are compatible to its venom, which is abundant in metalloproteases (svMPs) and C-type lectin-like proteins. In this study, we investigated geographic variations in the venom of D. acutus collected from Taiwan and four Mainland Chinese provinces: Fujian, Jiangxi, Anhui, and Hunan. The variations were assessed through high-performance liquid chromatography, non-metric multidimensional scaling analysis, gel electrophoresis, and enzyme-linked immunosorbent assay (ELISA) with a monospecific antivenom (DaMAV) generated against the Taiwanese D. acutus venom, and discussed based on venom-protein sequences in databases and literature related to D. acutus venom. Additionally, the cross-reactivity of DaMAV against Crotalus horridus and Calloselasma rhodostoma venoms was investigated. We noted differential abundances of D. acutus venom metalloproteases, C-type lectin-like proteins, and phospholipase A2, along with point mutations and selective expression of serine protease isoforms. The ELISA results revealed that the venom from Taiwan was more reactive toward Taiwanese DaMAV than the four Mainland Chinese venoms, consistent with chromatographic profile differences, whereas C. horridus venom presented moderate cross-reactivity with DaMAV. The observed immunoreactivities of these venom with DaMAV can be attributed to the high prevalence of their PIII-svMPs, which are the dominant antigens, and the conservation of PIII-svMP epitopes.

Incidence and Risk Factors for Wound Infections after Trimeresurus stejnegeri Snakebites in Taiwan

Snakebite envenomation is a neglected tropical disease. Taiwan, with its subtropical and Southeast Asian environment, provides suitable habitat for several venomous snake species. Trimeresurus stejnegeri, an arboreal pit viper, is the most common cause of venomous snakebite in Taiwan. Trimeresurus stejnegeri envenomation can cause local swelling, occasional ecchymosis, and wound infection. The primary treatment of T. stejnegeri envenomation is the binary antivenom, vacuum freeze-dried F(ab')2 fragments of equine antibodies, against T. stejnegeri and Protobothrops mucrosquamatus. This study aimed to analyze the incidence of post-envenomation wound infections caused by T. stejnegeri based on data collected over a decade from institutions affiliated with the Chang Gung Memorial Hospital in Taiwan. A total of 254 patients were enrolled in this study. Clinical and laboratory data, treatment information, and patient outcomes were extracted from electronic medical records. Wound infection was associated with delay in antivenom initiation (adjusted odds ratio: 3.987; 95% CI: 1.406-11.302). The infection rates were 20.5%, 12.5%, 31.3%, and 48.1% for antivenom administration within 2 hours, 2-4 hours, 4-6 hours, and > 6 hours, respectively. Therefore, early initiation of antivenom treatment (within 6 hours) is recommended. Morganella morganii was cultured from wounds of the patients, whereas Enterobacter cloacae and Enterococcus faecalis were cultured from both the oral cavity of snakes and the wounds of the patients. For post-envenomation patients who develop a local infection, empiric antibiotics such as third-generation cephalosporins, quinolones, and piperacillin/tazobactam are recommended because snakebite wound infections are often polymicrobial in nature.

Proteomic characteristics of six snake venoms from the Viperidae and Elapidae families in China and their relation to local tissue necrosis

Patients envenomed by snakes from the Viperidae and Elapidae families in China often have varying degrees of local tissue necrosis. Due to the relative clinical characteristics of local tissue necrosis and ulceration following envenoming, this study has analyzed the proteome of six snake venoms from the Viperidae and Elapidae family, and the toxin profiles of each snake were compared and correlated with the clinical manifestations that follow cytotoxic envenoming. Deinagkistrodon acutus and Naja atra envenomation induce severe ulceration, which is absent in Bungarus multicinctus envenomation and mild in the other three vipers. It is interesting to note that the proportion of c-type lectins (CTL) (20.63%) in Deinagkistrodon acutus venom was relatively high, which differs from the venom of other vipers. In addition, three-fingered toxin (3FTx) (2.15%) is present in the venom of Deinagkistrodon acutus, but has not been detected in the remaining three vipers. Snake venom metalloprotease (SVMP) (34.4%-44.7%), phospholipase A2 (PLA2) (9.81%-40.83%), and snake venom serine protease (SVSP) (9.44%-16.2%) represent the most abundant families of toxin in Viperidae venom. The Elapidae venom proteome was mainly composed of neurotoxins and cytotoxins, including 3FTx (39.28%-60.08%) and PLA2 (8.24%-58.95%) toxins, however, the proportion of CRISPS (26.36%) in Naja atra venom was relatively higher compared to Bungarus multicinctus venom. Significant differences in SVMP, SVSP, and 3FTx expression levels exist between the Viperidae and the Elapidae family. The main toxins responsible for the development of tissue necrosis and ulcerations following Viperidae envenoming are hematotoxins (SVSMP, SVSP) and myotoxins (PLA2). Deinagkistrodon acutus venom contains high levels of CTL and traces of 3FTx, leading to more severe local necrosis. However, Naja atra venom can also cause severe local necrosis through the effects of myotoxin (3FTx, CRISP, PLA2). Bungarus multicinctus venom does not contain myotoxins, resulting in pure systemic neurological manifestations no obvious necrosis of local tissue in patients.

Comparisons of the Oral Microbiota from Seven Species of Wild Venomous Snakes in Taiwan Using the High-Throughput Amplicon Sequencing of the Full-Length 16S rRNA Gene

A venomous snake's oral cavity may harbor pathogenic microorganisms that cause secondary infection at the wound site after being bitten. We collected oral samples from 37 individuals belonging to seven species of wild venomous snakes in Taiwan, including Naja atra (Na), Bungarus multicinctus (Bm), Protobothrops mucrosquamatus (Pm), Trimeresurus stejnegeri (Ts), Daboia siamensis (Ds), Deinagkistrodon acutus (Da), and alpine Trimeresurus gracilis (Tg). Bacterial species were identified using full-length 16S rRNA amplicon sequencing analysis, and this is the first study using this technique to investigate the oral microbiota of multiple Taiwanese snake species. Up to 1064 bacterial species were identified from the snake's oral cavities, with 24 pathogenic and 24 non-pathogenic species among the most abundant ones. The most abundant oral bacterial species detected in our study were different from those found in previous studies, which varied by snake species, collection sites, sampling tissues, culture dependence, and analysis methods. Multivariate analysis revealed that the oral bacterial species compositions in Na, Bm, and Pm each were significantly different from the other species, whereas those among Ts, Ds, Da, and Tg showed fewer differences. Herein, we reveal the microbial diversity in multiple species of wild snakes and provide potential therapeutic implications regarding empiric antibiotic selection for wildlife medicine and snakebite management.

Nationwide and long-term epidemiological research of snakebite envenomation in Taiwan during 2002-2014 based on the use of snake antivenoms: A study utilizing National Health Insurance Database

INTRODUCTION

In Taiwan, six venomous snake species with medical importance have been found; however, long-term epidemiological data of snakebite envenomation (SBE) is lacking. This study aimed to explore the epidemiology of SBE based on the distribution and use of different antivenoms in different parts of Taiwan to facilitate the development of prevention strategies and resource allocation.

METHODS AND RESULTS

This retrospective study was conducted using the Taiwan National Health Insurance Research Database from 2002 to 2014. A total of 12,542 patients were treated with antivenoms. The directly standardized cumulative incidence was 3.6 cases per 100,000 individuals based on the 2000 World Standard Population. The incidence of SBEs peaked in the summer (35.9%). The relative risk (RR) of male patients versus female patients was 2.5 (p < 0.0001). The RRs of patients aged 18-64 and ≥65 years versus those aged <18 years were 6.0 (p < 0.0001) and 14.3 (p < 0.0001), respectively. Furthermore, the RR of eastern Taiwan versus northern Taiwan was 6.8 (p < 0.0001). The RR of agricultural workers versus laborers was 5.5 (p < 0.0001). Compared with patients envenomed by Trimeresurus stejnegeri stejnegeri or Protobothrops mucrosquamatus, those envenomed by Naja atra or Bungarus multicinctus multicinctus were more likely to occur in central (adjusted odds ratio [aOR] = 2.6, p < 0.0001) or southern (aOR = 3.2, p < 0.0001) Taiwan, but less frequently among agricultural workers (aOR = 0.6, p < 0.0001). The overall case-fatality rate was 0.11%.

CONCLUSIONS

Among Asian countries, Taiwan had low incidence and case-fatality rates of SBE. Risk factors included male gender, old age, summer season, being in eastern Taiwan, and being an agricultural worker. Differences of the epidemiological findings between snake species should be focused on when developing strategies for snakebite prevention.

Immunoprofiling of Equine Plasma against Deinagkistrodon acutus in Taiwan: Key to Understanding Differential Neutralization Potency in Immunized Horses

Snakebite envenoming is a public health issue linked to high mortality and morbidity rates worldwide. Although antivenom has been the mainstay treatment for envenomed victims receiving medical care, the diverse therapeutic efficacy of the produced antivenom is a major limitation. Deinagkistrodon acutus is a venomous snake that poses significant concern of risks to human life in Taiwan, and successful production of antivenom against D. acutus envenoming remains a considerable challenge. Among groups of horses subjected to immunization schedules, few or none subsequently meet the quality required for further scale-up harvesting. The determinants underlying the variable immune responses of horses to D. acutus venom are currently unknown. In this study, we assessed the immunoprofiles of high-potency and low-potency horse plasma against D. acutus venom and explored the conspicuous differences between these two groups. Based on the results of liquid chromatography with tandem mass spectrometry (LC-MS/MS), acutolysin A was identified as the major component of venom proteins that immunoreacted differentially with the two plasma samples. Our findings indicate underlying differences in antivenoms with variable neutralization efficacies, and may provide valuable insights for improvement of antivenom production in the future.

Platelet Desialylation Is a Novel Mechanism and Therapeutic Target in Daboia siamensis and Agkistrodon halys Envenomation-Induced Thrombocytopenia

Venom-induced thrombocytopenia (VIT) is one of the most important hemotoxic effects of a snakebite, which is often associated with venom-induced consumptive coagulopathy (VICC). Refractory thrombocytopenia without significant coagulation abnormalities has also been reported after envenomation by some viperid snakes; however, the mechanisms are not well understood and therapeutic strategies are lacking. Here, we found that patients injured by Daboia siamensis or Agkistrodon halys snakes, who were resistant to standard antivenom treatment, had developed coagulopathy-independent thrombocytopenia. Venoms from these viperid snakes, rather than from the elapid snake (Bungarus multicinctus), induced platelet surface expression of neuraminidase-1 (NEU-1), and significantly increased the desialylation of the glycoproteins on human platelets. The desialylated platelets caused by viperid snake venoms were further internalized by macrophages, which resulted in reduced platelet numbers in peripheral blood. Importantly, neuraminidase inhibitor significantly decreased viper venom-induced platelet desialylation, therefore inhibiting platelet phagocytosis by macrophages, and alleviating venom-induced thrombocytopenia. Collectively, these findings support an important role for desialylated platelet clearance in the progression of viper envenomation-induced, coagulopathy-independent thrombocytopenia. Our study demonstrates that the neuraminidase inhibitor may be a potential therapy or adjuvant therapy to treat snakebite-induced thrombocytopenia.

Bacteriological Studies of Venomous Snakebite Wounds in Hangzhou, Southeast China

Snakebite is a common occurrence in Hangzhou, and identifying bacteria in wounds is very important for snakebite treatment. To define the pattern of wound bacterial flora of venomous snakebites and their susceptibility to common antibiotics, we reviewed the medical charts of patients admitted with snakebite at Hangzhou TCM Hospital from January 2019 to December 2020. A total of 311 patients were enrolled in this study. Among them, bacteria culture was positive in 40 patients, and 80 organisms were isolated. The most frequent pathogens were Morganella morganii and Staphylococcus aureus. According to the results of susceptibility testing, a majority of the isolates were resistant to some common first-line antibiotics, such as ampicillin, ampicillin/sulbactam, amoxicillin/clavulanic acid, cefoxitin, and cephazolin. Quinolones, however, have shown a better antibacterial effect. In conclusion, snakebite wounds involve a wide range of bacteria. Fluoroquinolones, such as levofloxacin and ciprofloxacin, could be an alternative for empirical treatment in patients with snakebite when the effect of other antibiotics is poor.

Oral Bacteria and Their Antibiotic Susceptibilities in Taiwanese Venomous Snakes

Wound infections after venomous snakebites are clinically important. Information regarding the nature and antibiotic susceptibilities of snake oral bacterial flora could support empiric antibiotic therapy. Wild venomous snakes were collected from southern Taiwan: a total of 30 each of Bungarus multicinctus, Naja atra, Protobothrops mucrosquamatus, and Trimeresurus stejnegeri; 3 Deinagkistrodon acutus; and 4 Daboia siamensis. The species and antibiotic susceptibilities of their oral bacteria were determined. Aerobic gram-negative bacteria, especially Pseudomonas aeruginosa and Proteus vulgaris, were the most abundant. Proteus vulgaris were more abundant in B. multicinctus, N. atra, and P. mucrosquamatus than in T. stejnegeri (40%, 43.3%, and 40% vs. 13.3%, respectively). The gram-negative species were less susceptible to first- and second-generation cephalosporins and ampicillin-sulbactam than to third-generation cephalosporins, fluoroquinolones, carbapenems, or piperacillin-tazobactam. The most abundant aerobic gram-positive species cultured was Enterococcus faecalis, which was more abundant in N. atra than in other snakes (p < 0.001) and was highly susceptible to ampicillin, high-level gentamicin, penicillin, teicoplanin, and vancomycin. Bacteroides fragilis and Clostridium species were the most common anaerobic bacteria. The anaerobic organisms were highly susceptible to metronidazole and piperacillin. As a reference for empiric antimicrobial therapy, third-generation cephalosporins, fluoroquinolones, carbapenems, or piperacillin-tazobactam can be initiated in venomous snakebites wound infections.

Personal Experience of Daboia siamensis Envenomation

Reports of envenomation induced by Daboia siamensis, a medically important venomous snake in Taiwan, are rare, and species identification might not be definitive. This article reports the complete course of a definite D. siamensis bite. The patient in this report was one of the authors who was bitten on the right palm near the base of the index finger by D. siamensis. The patient experienced local effects, neurological manifestations, and acute kidney injury. The laboratory analysis revealed elevated D-dimer and coagulopathy. The patient was administered 8 vials of antivenom and did not undergo surgical intervention or endotracheal tube intubation, but serum sickness occurred 8 days after antivenom administration. The horse immunoglobulin produced by the Centers for Disease Control, R. O. C. (Taiwan), against D. siamensis was effective and safe in the treatment of the patient. However, the best antivenom administration strategy remains unclear and requires further study.

A Biochemical and Pharmacological Characterization of Phospholipase A2 and Metalloproteinase Fractions from Eastern Russell's Viper (Daboia siamensis) Venom: Two Major Components Associated with Acute Kidney Injury

Acute kidney injury (AKI) following Eastern Russell's viper (Daboia siamensis) envenoming is a significant symptom in systemically envenomed victims. A number of venom components have been identified as causing the nephrotoxicity which leads to AKI. However, the precise mechanism of nephrotoxicity caused by these toxins is still unclear. In the present study, we purified two proteins from D. siamensis venom, namely RvPLA2 and RvMP. Protein identification using LCMS/MS confirmed the identity of RvPLA2 to be snake venom phospholipase A2 (SVPLA2) from Thai D. siamensis venom, whereas RvMP exhibited the presence of a factor X activator with two subunits. In vitro and in vivo pharmacological studies demonstrated myotoxicity and histopathological changes of kidney, heart, and spleen. RvPLA2 (3-10 µg/mL) caused inhibition of direct twitches of the chick biventer cervicis muscle preparation. After administration of RvPLA2 or RvMP (300 µg/kg, i.p.) for 24 h, diffuse glomerular congestion and tubular injury with minor loss of brush border were detected in envenomed mice. RvPLA2 and RvMP (300 µg/kg; i.p.) also induced congestion and tissue inflammation of heart muscle as well as diffuse congestion of mouse spleen. This study showed the significant roles of PLA2 and SVMP in snake bite envenoming caused by Thai D. siamensis and their similarities with observed clinical manifestations in envenomed victims. This study also indicated that there is a need to reevaluate the current treatment strategies for Thai D. siamensis envenoming, given the potential for irreversible nephrotoxicity.

Unexpected death in a young man associated with a unilateral swollen leg: Pathological and toxicological findings in a fatal snakebite from Deinagkistrodon acutus (Chinese moccasin)

Deinagkistrodon acutus (D. acutus), also known as the Chinese moccasin, is a viper species found throughout the southeastern parts of China, northern Vietnam and Laos. D. acutus envenomation can result in coagulopathy and lead to death if not treated correctly. A 20-year-old man was discovered with a severely swollen left thigh with overlying dark purple, discolored skin. He was immediately transported to hospital. Laboratory examinations revealed dysfunctional coagulation and fluid-electrolyte imbalances. He died 2 h later despite resuscitation efforts. Surveillance footage revealed that he had walked through a grass field while returning home that night. Autopsy and pathological examination findings revealed a large area of muscle necrosis of the left thigh, renal tubular necrosis, and hepatocyte necrosis. Potential fang marks were found on the decedent's jeans. Due to our suspicions, we performed specific enzyme-linked immunosorbent assays (ELISA) and detected D. acutus venom in the kidneys, left thigh muscle, liver, lung, spleen, and heart tissues of the decedent. In conclusion, the clinical manifestations, autopsy, histopathological examination, ELISA, and investigation results confirmed D. acutus envenomation.

Neutralising effects of small molecule toxin inhibitors on nanofractionated coagulopathic Crotalinae snake venoms

Repurposing small molecule drugs and drug candidates is considered as a promising approach to revolutionise the treatment of snakebite envenoming. In this study, we investigated the inhibiting effects of the small molecules varespladib (nonspecific phospholipase A2 inhibitor), marimastat (broad spectrum matrix metalloprotease inhibitor) and dimercaprol (metal ion chelator) against coagulopathic toxins found in Crotalinae (pit vipers) snake venoms. Venoms from Bothrops asper, Bothrops jararaca, Calloselasma rhodostoma and Deinagkistrodon acutus were separated by liquid chromatography, followed by nanofractionation and mass spectrometry identification undertaken in parallel. Nanofractions of the venom toxins were then subjected to a high-throughput coagulation assay in the presence of different concentrations of the small molecules under study. Anticoagulant venom toxins were mostly identified as phospholipases A2, while procoagulant venom activities were mainly associated with snake venom metalloproteinases and snake venom serine proteases. Varespladib was found to effectively inhibit most anticoagulant venom effects, and also showed some inhibition against procoagulant toxins. Contrastingly, marimastat and dimercaprol were both effective inhibitors of procoagulant venom activities but showed little inhibitory capability against anticoagulant toxins. The information obtained from this study aids our understanding of the mechanisms of action of toxin inhibitor drug candidates, and highlights their potential as future snakebite treatments.

Identifying the snake: First scoping review on practices of communities and healthcare providers confronted with snakebite across the world

BACKGROUND

Snakebite envenoming is a major global health problem that kills or disables half a million people in the world's poorest countries. Biting snake identification is key to understanding snakebite eco-epidemiology and optimizing its clinical management. The role of snakebite victims and healthcare providers in biting snake identification has not been studied globally.

OBJECTIVE

This scoping review aims to identify and characterize the practices in biting snake identification across the globe.

METHODS

Epidemiological studies of snakebite in humans that provide information on biting snake identification were systematically searched in Web of Science and Pubmed from inception to 2nd February 2019. This search was further extended by snowball search, hand searching literature reviews, and using Google Scholar. Two independent reviewers screened publications and charted the data.

RESULTS

We analysed 150 publications reporting 33,827 snakebite cases across 35 countries. On average 70% of victims/bystanders spotted the snake responsible for the bite and 38% captured/killed it and brought it to the healthcare facility. This practice occurred in 30 countries with both fast-moving, active-foraging as well as more secretive snake species. Methods for identifying biting snakes included snake body examination, victim/bystander biting snake description, interpretation of clinical features, and laboratory tests. In nine publications, a picture of the biting snake was taken and examined by snake experts. Snakes were identified at the species/genus level in only 18,065/33,827 (53%) snakebite cases. 106 misidentifications led to inadequate victim management. The 8,885 biting snakes captured and identified were from 149 species including 71 (48%) non-venomous species.

CONCLUSION

Snakebite victims and healthcare providers can play a central role in biting snake identification and novel approaches (e.g. photographing the snake, crowdsourcing) could help increase biting snake taxonomy collection to better understand snake ecology and snakebite epidemiology and ultimately improve snakebite management.