Venom-induced Consumption Coagulopathy Research Articles

The identification of a novel compound heterozygous mutation in hereditary human coagulation factor VII deficiency following a bamboo leaf green snake bite.

Hereditary factor VII (FVII) deficiency is an uncommon autosomal recessive disorder associated with mutations in the F7 gene, and laboratory investigations usually reveal isolated prolongation in prothrombin time (PT)/international normalized ratio (INR). Venom-induced consumptive coagulopathy (VICC) is distinguished by the activation of the coagulation pathway, which is triggered by procoagulant toxins in snake venom. Diagnosing snakebites in patients with hereditary FVII deficiency presents a challenge because prolonged time PT/INR is considered the most valuable diagnostic method for VICC. Therefore, it is possible that certain patients may not promptly receive an accurate diagnosis of hereditary FVII deficiency. We present a pedigree featuring hereditary FVII deficiency, which was diagnosed through Sanger sequencing, following a bamboo leaf green snake bite.

Clinical characteristics of snakebite patients attending a tertiary hospital in Hangzhou, southeast China.

Venomous snakebite is a neglected yet an important public health problem in China, and few studies have focused on them so far. The aim of this study is to investigate clinical characteristics of snakebites patients in a tertiary hospital in Hangzhou, southeast China. A total of 416 snakebite cases were included in this retrospective study. The data were collected from the medical records including demographics, clinical manifestations, management and outcomes. Of the 416 patients with venomous snakebites, 248 were male, and the average age was 54.6 years. The majority of cases occurred in rural in May to September. Out of all the venomous bites, Gloydius brevicaudus accounted for the highest percentage (55.3%). Hands were the most vulnerable site to snakebites (47.4%). Patients had clinical manifestations of pain (100%), swelling (100%), wound necrosis (25.7%), hemorrhagic blister (18.3%), and blister (8.7%). Three hundred and ninety-two patients received antivenom administration, and most were treated within six hours after bites. Twenty-six patients received surgical treatments, and 90 patients developed venom-induced consumption coagulopathy. No deaths have occurred in this study. Hangzhou is one of the regions with high affecting of snakebites in China. The results of this study will increase the understanding of the clinical characteristics of venomous snakebites in Hangzhou area.

Hypothetical Interventions to Prevent Acute Kidney Injury After Humpnosed Pit Viper Bite

Abstract: Even though the Hump-nosed pit viper bite is the commonest venomous snake bite in Sri Lanka, antivenoms with specific activity against it are not available. Acute kidney injury (A.K.I.) is an important systemic complication accounting for mortality. Therapeutic plasma exchange (TPE) and fresh frozen plasma (F.F.P.) are two interventional options hypothesized to prevent A.K.I. This is by TPE at-tenuating venom antigenemia and F.F.P. by inhibiting nephrotoxic renal injury by immunomodulation, and the additional benefit of replenishment of depleted clotting factors triggered by venom-induced con-sumption coagulopathy implicated in the multifactorial mechanisms of renal injury. Routine interventions on all envenomed patients are not justifiable owing to the rarity and sporadic occurrence of systemic complications, and only patients with coagulopathy should be selected for interventions. The benefit of preventing A.K.I. is most likely with early intervention at the inception of coagulopathy.

Neutralization, by a polyspecific antivenom, of the coagulopathy induced by the venom of Bothrops asper: Assessment by standard coagulation tests and rotational thromboelastometry in a murine model

Venom-induced consumption coagulopathy and thrombocytopenia are common and potentially severe manifestations of viperid snakebite envenoming since they contribute to local and systemic hemorrhage. Therefore, the assessment of the efficacy of antivenoms to neutralize coagulopathic and thrombocytopenic toxins should be part of the preclinical evaluation of these drugs. To evaluate the efficacy of the polyvalent (Crotalinae) antivenom produced in Costa Rica, in this study we have used a mouse model of coagulopathy and thrombocytopenia induced by the venom of Bothrops asper, based on the bolus intravenous (i.v.) injection of venom. When venom and antivenom were incubated before injection, or when antivenom was administered i.v. immediately after venom injection, venom-induced hemostatic alterations were largely abrogated. We also studied the recovery rate of clotting parameters in conditions where antivenom was administered when mice were coagulopathic. Some parameters recovered more rapidly in antivenom-treated mice than in control envenomed animals, but others showed a spontaneous recovery without antivenom. This is due to a rapid clearance of plasma venom levels in these experimental conditions. This implies that models based on the bolus i.v. injection of venom have limitations for assessing the effect of antivenom in the recovery of clotting alterations once coagulopathy has developed. It is suggested that alternative models should be developed based on a slower systemic absorption of venom. Overall, our findings provide a protocol for the preclinical evaluation of antivenoms and demonstrate that the polyvalent antivenom is effective in neutralizing the toxins of B. asper venom responsible for coagulopathy and thrombocytopenia.

Long-term health manifestations of hump-nosed pit viper (Genus: Hypnale) bites

Introduction The hump-nosed pit viper (Genus: Hypnale) is a highly medically significant snake in Sri Lanka, responsible for the majority of venomous snakebites (22–77%). They are found throughout Sri Lanka and the Western Ghats region of India. The venom can lead to two types of effects: acute and long-term. Acutely, bites often result in local symptoms, with less common systemic effects such as acute kidney injury, venom-induced consumption coagulopathy, and thrombotic microangiopathy. Methods We conducted a prospective observational study at Teaching Hospital Ratnapura, Sri Lanka, spanning six years, starting in June 2015. Patients bitten by hump-nosed pit vipers were followed up for two years, with assessments every three months to identify long-term effects. Data was gathered through interviewer-administered questionnaires. Results Out of 728 patients bitten by hump-nosed pit vipers, 22 (3%) were lost to follow-up. Forty-four (6.2%) experienced long-term effects, including chronic kidney disease (24; 3.4%), chronic wounds (five; 0.7%), amputations (five; 0.7%), fasciotomy-related wounds (four; 0.6%), and psychological illnesses (four; 0.6%). There were nine (1.3%) deaths in this group. Among those with chronic effects, 27 (61%) were males, and 17 (39%) were females, with ages ranging from 29 to 82 years (mean 57.6 years). The time it took to diagnose acute kidney injury from the snakebite was 18 h (interquartile range: 15–23.5 h), while the time to diagnose chronic kidney disease was 69 days (interquartile range: 64–74.75 days). In these patients, the estimated glomerular filtration rate was 29.3 mL/min/1.73 m2 (interquartile range: 14–50.75 mL/min/1.73 m2). Among the patients who did not develop long-term complications (662; 91%) 660 (90.7%) experienced local effects, and 82 (11.3%) developed systemic manifestations, including acute kidney injury in 60 (8%) and coagulopathy in 35 (5%). Conclusion Following hump-nosed pit viper bites, a subset of patients may experience long-term health complications, including chronic kidney disease, chronic ulcers, amputations, fasciotomy-related wounds, and psychological illnesses, with chronic kidney disease being the most frequently observed among these manifestations.

Suspected snakebite in a tertiary referral centre in Western Sydney: a 10-year case series

ABSTRACT We aimed to determine the epidemiology and clinical management of patients presenting to an Australian tertiary emergency department (ED) with a suspected snake bite. Nepean Hospital covers a geographical area known to harbour venomous elapid snake species. A Retrospective chart review of all patients presenting to Nepean ED from 2011 to 2020 was performed. We searched the electronic medical records (eMR) for triage presentations including search terms of “snakebite”, “bite” “envenomation”, or “bite-snake” and a discharge or independent diagnosis of “snakebite” or “envenomation”. Our review identified 110 patients presenting with snakebite, of whom nine had signs or symptoms indicating envenomation. The most common envenomation syndrome was venom-induced consumption coagulopathy (VICC) and the most commonly suspected culprit snake was the Eastern Brown Snake. Our data broadly agreed with national data on epidemiology and demographics. We noted a satisfactory rate of compliance with local snake bite protocols with evidence of early diagnosis and antivenom administration. We had no cases of anaphylaxis and one case of serum sickness. Our study of a tertiary hospital experience in the management of snake bite demonstrated an appropriate adherence to national guidelines and early clinician recognition of envenomation syndromes. It also demonstrated appropriate antivenom use without obvious time delay.

Prevalence of Thrombotic Microangiopathy Among Patients With Snake Bite-Induced Hemotoxic Clinical Syndrome in the Hills of Himachal Pradesh, India

ABSTRACT Objective: Snakebite envenomation-related thrombotic microangiopathy (TMA) is observed in a subset of patients with venom-induced consumption coagulopathy (VICC). The study was planned to determine the prevalence of TMA among patients with hemotoxic envenomation admitted to a medical college hospital in Himachal Pradesh, India. Methods: This was a hospital-based open cohort observational study conducted on patients diagnosed with hemotoxic envenomation. The study period was of 1 year and patients were recruited using a nonprobability sampling method. Hemotoxic envenomation was defined as prolonged bedside 20-min whole blood clotting time (20 WBCT) following a history of snake bites. TMA was defined as the triad of microangiopathic hemolytic anemia (MAHA), thrombocytopenia, and acute kidney injury (AKI). Results: A total of 56 patients (32 females and 24 males) were included in the study. The prevalence of TMA was (7/56) 12.5%. Out of the seven patients with TMA, four (57.1%) patients improved without renal replacement therapy and three (42.9%) patients took referrals for getting nephrology services outside the state and hence were lost in follow-up. AKI was developed in 17 (30%) patients. Conclusion: The study demonstrated that TMA is not an uncommon entity. Investigation protocol for TMA should be included in all patients with VICC.

Comparing modified Lee and White method against 20-minute whole blood clotting test as bedside coagulation screening test in snake envenomation victims.

Twenty-minute whole blood clotting test (20WBCT) and Modified Lee and White (MLW) method are the most routinely employed bedside tests for detecting coagulopathic snake envenomation. Our study compared the diagnostic utility of MLW and 20WBCT for snakebite victims at a tertiary care hospital in Central Kerala, South India. This single-center study recruited 267 patients admitted with snake bites. 20WBCT and MLW were performed simultaneously at admission along with the measurement of Prothrombin Time (PT). The diagnostic utility of 20WBCT and MLW was determined by comparing the sensitivity (Sn), specificity (Sp), positive and negative predictive values, likelihood ratios, and accuracy at admission with an INR value > 1.4. Out of 267 patients, 20 (7.5%) patients had VICC. Amongst those who had venom-induced consumption coagulopathy (VICC), MLW was prolonged for 17 patients, (Sn 85% 95% confidence interval [CI]: 61.1-96.0) whereas 20WBCT was abnormal for 11 patients (Sn 55%, 95% CI: 32.04-76.17). MLW and 20WBCT were falsely positive for the same patient (Sp 99.6%, 95% CI: 97.4-99.9%). MLW is more sensitive than 20WBCT to detect coagulopathy at the bedside amongst snakebite victims. However, further studies are necessary for standardizing bedside coagulation tests in snakebite cases.

Neuroparalytic snake bite masquerading as acute abdominal pain in children

Background: Neurotoxic snakebite (usually by the krait) presents with abdominal colic and chest pain as a common premonitory sign of envenomation. Being a nocturnal snake, the time of unprovoked painless biting is usually at night and the victims are individuals sleeping on the ground. Thus, history is usually not forthcoming. Snakebite causes morbidity (neuroparalytic, myopathic, vasculopathic, venom-induced consumption coagulopathy, cardiotoxic, nephrotoxic, etc.), and mortality if not given timely treatment with anti-snake venom (ASV), the only specific treatment. Clinical Description: We present four children from a rural background who were admitted successively over a month during the last rainy season. They initially became symptomatic with acute abdominal pain from midnight to early morning time and developed neuroparalytic manifestations within a few hours. On exclusion of other causes by clinical evaluation, we suspected snakebite envenomation though there was no witnessing of the event or evidence of fang bites. Investigations to rule out commonly associated organ dysfunction were ordered. Management: All children were given supportive therapy. Three cases required mechanical ventilation. The first two received ASV relatively late as the suspicion of snakebite was not considered initially. In the third case, the administration of ASV was early and the hospital stay was shorter. The fourth case received ASV at a peripheral health center and was referred in case he required ventilator support. However, his neuroparalysis did not progress to respiratory failure and he was discharged the earliest. Conclusions: Clinicians should consider snakebite in children belonging to rural areas who present with acute abdominal pain during the rainy season, and monitor for signs of neurotoxicity and other clinical manifestations of snake envenomation. A high index of suspicion should be kept, as definitive treatment with ASV results in early recovery without any sequelae, and reduces mortality.

Venom-induced consumptive coagulopathy leading to thrombotic microangiopathy following Echis carinatus sochureki bite: is snake antivenom effective?

The incidence of thrombotic microangiopathy (TMA) following snake bite is reported to be ranging from 3.6 to 15%. We report a 10-year-old boy who developed TMA and due to venom-induced consumptive coagulopathy (VICC) despite receiving adequate and timely doses of snake antivenom following a bite of saw-scaled viper (Echis carinatus sochureki). VICC was managed by plasmapheresis. Though snake bite envenomation-associated renal complications are not uncommon, possibility of TMA should be considered early during management. Our patient developed TMA with subsequent acute cortical necrosis after saw-scaled viper bite despite an adequate and timely dose of snake antivenom which emphasizes the ineffectiveness of antivenom against the venom of given snake species leading to long-term complications.

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.

Comparison of bedside clotting tests for detecting venom-induced consumption coagulopathy following Sri Lankan viper envenoming

Background The whole blood clotting test (WBCT) is commonly used for diagnosing venom-induced consumption coagulopathy (VICC) in resource-poor settings. We aimed to investigate the diagnostic accuracy of the WBCT and capillary blood clotting test (CBCT) for detecting VICC in viper envenoming in Sri Lanka. Methods All confirmed snakebites admitted to Teaching Hospital Anuradhapura from July 2020 to June 2021 were included. On admission, WBCTs after 15, 20 and 25 min observation times (WBCT-15, WBCT-20 and WBCT-25) and CBCT observed in 30 s intervals (CBCT-t), 5 and 10 min CBCT (CBCT-5 and CBCT-10) were done. Blood was collected simultaneously for prothrombin time (PT)/international normalized ratio (INR) and plasma fibrinogen. We defined VICC as an INR >1.5 (Incomplete VICC = INR>1.5 and complete VICC = ≥3.0). Results A total of 272 confirmed snakebites (Russell’s viper[76], hump-nosed viper[89], non-venomous snakes[51] and unidentified bites[56]) were recruited (median age: 42 y [interquartile range: 30- 53 y]; 189 males [69%]). On admission, 82 (30%) had incomplete VICC (INR >1.5 and <3) and 77 (28%) had complete VICC (INR ≥3). Sixteen (6%) developed clinically apparent bleeding. The WBCT-15 had the best sensitivity of 47% for detecting VICC and 68% for complete VICC. The sensitivities of the WBCT-20, WBCT-25, CBCT-5 and CBCT-10 was 30–35%. The sensitivities of all tests were better in detecting complete VICC, VICC in Russell’s viper bites and more than 2 h post-bite. The WBCT-15 test had a sensitivity of 76% for VICC in confirmed Russell’s viper bites. For detection of VICC, CBCT-t had an an excellent sensitivity of 97%, but a poor specificity of 35% for an optimal cut-off of >6.25 min. Conclusion WBCTs are poorly diagnostic for VICC in Russell’s viper and hump-nosed viper envenoming, missing up to two-thirds of patients for some tests. The WBCT-15 was the best test, improving for more severe VICC and greater than 2 h post-bite.

Fibrinogenolysis in Venom-Induced Consumption Coagulopathy after Viperidae Snakebites: A Pilot Study.

Envenomations that are caused by Viperidae snakebites are mostly accompanied by venom-induced consumption coagulopathy (VICC) with defibrination. The clinical course of VICC is well described; however, reports about its detailed effects in the hemocoagulation systems of patients are sparse. In this pilot study, we prospectively analyzed the changes in plasma fibrinogen that were caused by the envenomation of six patients by five non-European Viperidae snakes. Western blot analysis was employed and fibrinogen fragments were visualized with the use of specific anti-human fibrinogen antibodies. All of the studied subjects experienced hypo- or afibrinogenemia. The western blot analysis demonstrated fibrinogenolysis of the fibrinogen chains in all of the cases. Fibrinogenolysis was considered to be a predominant cause of defibrination in Crotalus, Echis, and Macrovipera envenomation; while, in the cases of VICC that were caused by Atheris and Calloselasma envenomation, the splitting of the fibrinogen chains was present less significantly.

Exploring the Utility of ssDNA Aptamers Directed against Snake Venom Toxins as New Therapeutics for Snakebite Envenoming.

Snakebite is a neglected tropical disease that causes considerable death and disability in the tropical world. Although snakebite can cause a variety of pathologies in victims, haemotoxic effects are particularly common and are typically characterised by haemorrhage and/or venom-induced consumption coagulopathy. Antivenoms are the mainstay therapy for treating the toxic effects of snakebite, but despite saving thousands of lives annually, these therapies are associated with limited cross-snake species efficacy due to venom variation, which ultimately restricts their therapeutic utility to particular geographical regions. In this study, we sought to explore the potential of ssDNA aptamers as toxin-specific inhibitory alternatives to antibodies. As a proof of principle model, we selected snake venom serine protease toxins, which are responsible for contributing to venom-induced coagulopathy following snakebite envenoming, as our target. Using SELEX technology, we selected ssDNA aptamers against recombinantly expressed versions of the fibrinogenolytic SVSPs ancrod from the venom of C. rhodostoma and batroxobin from B. atrox. From the resulting pool of specific ssDNA aptamers directed against each target, we identified candidates that exhibited low nanomolar binding affinities to their targets. Downstream aptamer-linked immobilised sorbent assay, fibrinogenolysis, and coagulation profiling experiments demonstrated that the candidate aptamers were able to recognise native and recombinant SVSP toxins and inhibit the toxin- and venom-induced prolongation of plasma clotting times and the consumption of fibrinogen, with inhibitory potencies highly comparable to commercial polyvalent antivenoms. Our findings demonstrate that rationally selected toxin-specific aptamers can exhibit broad in vitro cross-reactivity against toxin isoforms found in different snake venoms and are capable of inhibiting toxins in pathologically relevant in vitro and ex vivo models of venom activity. These data highlight the potential utility of ssDNA aptamers as novel toxin-inhibiting therapeutics of value for tackling snakebite envenoming.

Exploring the Utility of Recombinant Snake Venom Serine Protease Toxins as Immunogens for Generating Experimental Snakebite Antivenoms.

Snakebite is a neglected tropical disease that causes high rates of global mortality and morbidity. Although snakebite can cause a variety of pathologies in victims, haemotoxic effects are particularly common and are typically characterised by haemorrhage and/or venom-induced consumption coagulopathy. Despite polyclonal antibody-based antivenoms being the mainstay life-saving therapy for snakebite, they are associated with limited cross-snake species efficacy, as there is often extensive toxin variation between snake venoms, including those used as immunogens for antivenom production. This restricts the therapeutic utility of any antivenom to certain geographical regions. In this study, we explored the feasibility of using recombinantly expressed toxins as immunogens to stimulate focused, pathology-specific, antibodies in order to broadly counteract specific toxins associated with snakebite envenoming. Three snake venom serine proteases (SVSP) toxins, sourced from geographically diverse and medically important viper snake venoms, were successfully expressed in HEK293F mammalian cells and used for murine immunisation. Analyses of the resulting antibody responses revealed that ancrod and RVV-V stimulated the strongest immune responses, and that experimental antivenoms directed against these recombinant SVSP toxins, and a mixture of the three different immunogens, extensively recognised and exhibited immunological binding towards a variety of native snake venoms. While the experimental antivenoms showed some reduction in abnormal clotting parameters stimulated by the toxin immunogens and crude venom, specifically reducing the depletion of fibrinogen levels and prolongation of prothrombin times, fibrinogen degradation experiments revealed that they broadly protected against venom- and toxin-induced fibrinogenolytic functional activities. Overall, our findings further strengthen the case for the use of recombinant venom toxins as supplemental immunogens to stimulate focused and desirable antibody responses capable of neutralising venom-induced pathological effects, and therefore potentially circumventing some of the limitations associated with current snakebite therapies.

D-dimer testing for early detection of venom-induced consumption coagulopathy after snakebite in Australia (ASP-29).

ObjectiveTo assess the accuracy and marginal value of quantitative D‐dimer testing for diagnosing venom‐induced consumption coagulopathy (VICC) in people bitten by Australian snakes.Design, settingAnalysis of data for suspected and confirmed cases of snakebite collected prospectively by the Australian Snakebite Project, 2005–2019, from 200 hospitals across Australia.Participants1363 patients for whom D‐dimer was quantitatively assessed within 24 hours of suspected or confirmed snakebite.Main outcome measuresDiagnostic performance of quantitative D‐dimer testing for detecting systemic envenoming with VICC (area under the receiver operating characteristic curve, AUC); optimal D‐dimer cut‐off value (maximum sum of sensitivity and specificity).ResultsD‐dimer values exceeded 2.5 mg/L within three hours of the bite for 95% of patients who developed VICC, and were lower than 2.5 mg/L for 95% of non‐envenomed patients up to six hours after snakebite. The AUC for diagnosing envenoming with VICC on the basis of quantitative D‐dimer testing within six hours of snakebite was 0.97 (95% CI, 0.96–0.98; 944 patients). Diagnostic performance increased during the first three hours after snakebite; for quantitative D‐dimer testing at 2–6 hours, the AUC was 0.99 (95% CI, 0.99–1.0); with a cut‐off of 2.5 mg/L, sensitivity was 97.1% (95% CI, 95.0–98.3%) and specificity 99.0% (95% CI, 97.6–99.6%) for VICC. For 36 patients with normal international normalised ratio (INR) and activated partial thromboplastin time (aPTT) values 2–6 hours after snakebite, the AUC was 0.97 (95% CI, 0.93–1.0); with a cut‐off of 1.4 mg/L, sensitivity was 94% (95% CI, 82–99%) and specificity 96% (95% CI, 94–97%). In all but one of 84 patients who developed VICC‐related acute kidney injury, D‐dimer values exceeded 4 mg/L within 24 hours of the bite.ConclusionD‐dimer concentrations assessed 2–6 hours after snakebite, with a cut‐off value of 2.5 mg/L, could be useful for diagnosing envenoming with VICC.

Coagulopathy induced by viperid snake venoms in a murine model: Comparison of standard coagulation tests and rotational thromboelastometry

Viperid snakebite envenoming is often characterized by a venom-induced consumption coagulopathy due to the procoagulant effect of venom components, resulting in the alteration of clotting laboratory tests. There is a growing trend to use rotational thromboelastometry in the assessment of clotting disturbances in a variety of pathologies, although its use in experimental models of envenoming has been limited. An in vivo murine model was implemented to assess the coagulopathy induced by three Central American viperid venoms which have different mechanisms of action on clotting factors, i.e., Bothrops asper, Crotalus simus and Bothriechis lateralis. Venom was injected by the intravenous route and blood samples were collected at 1, 3, 5 and 24 h after envenoming. Coagulopathy was assessed by standard clotting tests and by routine rotational thromboelastometric parameters. In addition, the changes in platelet number were followed. B. asper and C. simus venoms induced coagulopathy and thrombocytopenia 1 h after injection, followed by a slow recovery at 3, 5 and 24 h, although the majority of clotting parameters were still significantly affected by 3 and 5 h, and were corrected by 24 h. In general, a similar time-course of alterations was observed for standard clotting tests and most rotational thromboelastomeric assays. However, some thromboelastometric parameters, especially those related to Fibtem, showed more drastic alterations than standard tests and remained altered even at 24 h in some cases. This is likely related to the low fibrinogen concentration observed at most time intervals. B. lateralis venom did not induce a consumption coagulopathy, although it caused a marked thrombocytopenia.

The Unusual Metalloprotease-Rich Venom Proteome of the Australian Elapid Snake Hoplocephalus stephensii.

The Australasian region is home to the most diverse elapid snake radiation on the planet (Hydrophiinae). Many of these snakes have evolved into unique ecomorphs compared to elapids on other continents; however, their venom compositions are poorly known. The Australian elapid Hoplocephalus stephensii (Stephen’s banded snake) is an arboreal snake with a unique morphology. Human envenoming results in venom-induced consumption coagulopathy, without neurotoxicity. Using transcriptomics and a multi-step fractionation method involving reverse-phase high-performance liquid chromatography, sodium dodecyl sulfate polyacrylamide gel electrophoresis and bottom-up proteomics, we characterized the venom proteome of H. stephensii. 92% of the total protein component of the venom by weight was characterized, and included all dominant protein families and 4 secondary protein families. Eighteen toxins made up 76% of the venom, four previously characterized and 14 new toxins. The four dominant protein families made up 77% of the venom, including snake venom metalloprotease (SVMP; 36.7%; three identified toxins), phospholipase A2 (PLA2; 24.0%; five identified toxins), three-finger toxin (3FTx; 10.2%; two toxins) and snake venom serine protease (SVSP; 5.9%; one toxin; Hopsarin). Secondary protein families included L-amino acid oxidase (LAAO; 10.8%; one toxin), natriuretic peptide (NP; 0.8%; two toxins), cysteine-rich secretory protein (CRiSP; 1.7%; two toxins), c-type lectin (CTL; 1.1%; one toxin), and one minor protein family, nerve growth factor (NGF; 0.8%; one toxin). The venom composition of H. stephensii differs to other elapids, with a large proportion of SVMP and LAAO, and a relatively small amount of 3FTx. H. stephensii venom appeared to have less toxin diversity than other elapids, with only 18 toxins making up three-quarters of the venom.

In vitro and in vivo preclinical venom inhibition assays identify metalloproteinase inhibiting drugs as potential future treatments for snakebite envenoming by Dispholidus typus.

Snakebite envenoming affects more than 250,000 people annually in sub-Saharan Africa. Envenoming by Dispholidus typus (boomslang) results in venom-induced consumption coagulopathy (VICC), whereby highly abundant prothrombin-activating snake venom metalloproteinases (SVMPs) consume clotting factors and deplete fibrinogen. The only available treatment for D. typus envenoming is the monovalent SAIMR Boomslang antivenom. Treatment options are urgently required because this antivenom is often difficult to source and, at US$6000/vial, typically unaffordable for most snakebite patients. We therefore investigated the in vitro and in vivo preclinical efficacy of four SVMP inhibitors to neutralise the effects of D. typus venom; the matrix metalloproteinase inhibitors marimastat and prinomastat, and the metal chelators dimercaprol and DMPS. The venom of D. typus exhibited an SVMP-driven procoagulant phenotype in vitro. Marimastat and prinomastat demonstrated equipotent inhibition of the SVMP-mediated procoagulant activity of the venom in vitro, whereas dimercaprol and DMPS showed considerably lower potency. However, when tested in preclinical murine models of envenoming using mixed sex CD1 mice, DMPS and marimastat demonstrated partial protection against venom lethality, demonstrated by prolonged survival times of experimental animals, whereas dimercaprol and prinomastat failed to confer any protection at the doses tested. The preclinical results presented here demonstrate that DMPS and marimastat show potential as novel small molecule-based therapeutics for D. typus snakebite envenoming. These two drugs have been previously shown to be effective against Echis ocellatus VICC in preclinical models, and thus we conclude that marimastat and DMPS should be further explored as potentially valuable early intervention therapeutics to broadly treat VICC following snakebite envenoming in sub-Saharan Africa.

Hemostatic Analysis of Simulated Gloydius ussuriensis Envenomation Using Canine Blood: A Comparison of Thromboelastography and Classical Coagulation Tests.

Simple SummarySnake bites in companion animals are a major issue and cause life-threatening hemorrhage. Classical coagulation tests are performed to diagnose snake venom-induced coagulopathy; however, these tests often fail to detect early coagulopathy. This in vitro study using snake venom and canine blood aimed to explore the efficacy of thromboelastography, which enabled a comprehensive assessment of the coagulation process, compared with classical coagulation tests. Our results identified the usefulness of thromboelastography in detecting early venom-induced coagulopathy compared with classical coagulation tests. This finding may facilitate decision making in relation to the immediate initiation of anti-venom treatment or suspending unnecessary anti-venom administration, which often causes adverse reactions.Snake envenomation may lead to venom-induced consumptive coagulopathy (VICC), usually diagnosed by classical coagulation tests (CCTs), such as prothrombin time (PT) and activated partial thromboplastin time (aPTT). However, the results of CCTs are frequently normal in the initial stages, which may delay anti-venom treatments. Thromboelastography (TEG) is a point-of-care and real-time diagnostic tool that enables a comprehensive assessment of the coagulation process. This in vitro study aimed to determine concentration-dependent changes in canine blood caused by Gloydius ussuriensis (G. ussuriensis) envenomation using TEG and CCTs. Lyophilized G. ussuriensis venom was reconstructed using mouse intravenous lethal dose 50 (LD50iv) and serially diluted to 25% LD50iv, 50% LD50iv, and 75% LD50iv to reproduce VICC at different concentrations. Normal saline was used for the control. We compared TEG values of the reaction time (R), kinetic time (K), rate of clot formation (α-angle), maximum amplitude (MA), fibrinolysis at 30 min (LY30), and global strength of the clot (G) with those of PT, aPTT, fibrinogen, and platelet counts (PLTs). Most TEG parameters, except R and LY30, demonstrated statistically significant changes compared with the control at all concentrations. CCTs, except PLTs, revealed significant changes at ≥50% LD50iv. Thus, TEG could be a useful diagnostic strategy for early VICC and preventing treatment delay.