Tiger snake (Notechis spp) envenoming: Australian Snakebite Project (ASP-13)

To bite the hand that feeds you: A case of thrombotic microangiopathy due to Tiger snake bite

This report details the case of a 51-year-old man with a Tiger snake bite who developed systemic envenomation, coagulopathy and thrombotic microangiopathy (TMA) requiring renal replacement therapy. He received plasma exchange as additional therapy while awaiting confirmation of the cause of the TMA. We discuss clinical decision making in detection of systemic envenomation and management of the rare complication of TMA, as well as current Australian guidelines around antivenom administration. This is the fourth known documented case of TMA from a Tiger snake bite in Australia.

Investigating skeletal muscle biomarkers for the early detection of Australian myotoxic snake envenoming: an animal model pilot study

INTRODUCTION

Myotoxicity is an important toxidrome that can occur with envenoming from multiple Australian snake types. Early antivenom administration is an important strategy to reduce the incidence and severity of myotoxicity. The current gold standard biomarker, serum creatine kinase activity, does not rise early enough to facilitate early antivenom administration. Several other skeletal muscle biomarkers have shown promise in other animal models and scenarios. The aim of this study was to examine the predictive values of six skeletal muscle biomarkers in a rat model of Australian snake myotoxicity.

METHODS

Sprague-Dawley rats were anaesthetised and administered either Pseudechis porphyriacus (red-bellied black snake) or Notechis scutatus (tiger snake) venom, or normal saline via intramuscular injection. Blood samples were collected. Assays were performed for serum creatine kinase skeletal muscle troponin-I concentration, skeletal muscle troponin-C concentration, myoglobin activity, skeletal muscle myosin light chain-1 concentration, and creatine kinase-MM activity. Serum markers were plotted against time, with comparison of area under the concentration (or activity)-time curve. The predictive values of six skeletal muscle biomarkers were examined using receiver operating characteristic curves.

RESULTS

There was no difference in area under the serum creatine kinase activity-time curve between venom and control groups. Serum creatine kinase-MM activity rose early in the venom treated rats, which had a significantly greater area under the serum activity-time curve. No difference in area under the serum concentration-time curve was demonstrated for the other biomarkers. Creatine kinase-MM activity had a superior predictive values than creatine kinase activity at 0-4 hours and 0-10 hours after venom administration, as indicated by area under the receiver operating characteristic curves (95 per cent confidence intervals) of 0.91 (0.78-1.00) and 0.88 (0.73-1.00) versus 0.79 (0.63-0.95) and 0.66 (0.51-0.80).

DISCUSSION

The limitations of serum creatine kinase activity in early detection of myotoxicity were demonstrated in this rat model.

CONCLUSION

Serum creatine kinase-MM activity was superior for early detection of Australian myotoxic snake envenoming.

Neuromuscular Weakness and Paralysis Produced by Snakebite Envenoming: Mechanisms and Proposed Standards for Clinical Assessment

Respiratory and airway-protective muscle weakness caused by the blockade of neuromuscular transmission is a major cause of early mortality from snakebite envenoming (SBE). Once weakness is manifest, antivenom appears to be of limited effectiveness in improving neuromuscular function. Herein, we review the topic of venom-induced neuromuscular blockade and consider the utility of adopting clinical management methods originally developed for the safe use of neuromuscular blocking agents by anesthesiologists in operating rooms and critical care units. Failure to quantify neuromuscular weakness in SBE is predicted to cause the same significant morbidity that is associated with failure to do so in the context of using a clinical neuromuscular block in surgery and critical care. The quantitative monitoring of a neuromuscular block, and an understanding of its neurophysiological characteristics, enables an objective measurement of weakness that may otherwise be overlooked by traditional clinical examination at the bedside. This is important for the initial assessment and the monitoring of recovery from neurotoxic envenoming. Adopting these methods will also be critical to the conduct of future clinical trials of toxin-inhibiting drugs and antivenoms being tested for the reversal of venom-induced neuromuscular block.

The Snake Study: Survey of National Attitudes and Knowledge in Envenomation

Despite recent reviews of best practice for the treatment of Australian venomous bites and stings, there is controversy about some aspects of care, particularly the use of antivenom. Our aim was to understand current attitudes and practice in the management of suspected snake envenoming. A single-stage, cross-sectional survey of Australian emergency care physicians who had treated snake envenomation in the previous 36 months was conducted. Hospital pharmacists were also invited to complete a survey about antivenom availability, usage, and wastage in Australian hospitals. The survey was available between 5 March and 16 June 2019. A total of 121 snake envenoming cases were reported, and more than a third (44.6%) of patients were not treated with antivenom. For those treated with antivenom (n = 67), 29 patients (43%) received more than one ampoule. Nearly a quarter of respondents (21%) identified that antivenom availability was, or could be, a barrier to manage snake envenoming, while cost was identified as the least important factor. Adverse reactions following antivenom use were described in 11.9% of cases (n = 8). The majority of patients with suspected envenoming did not receive antivenom. We noted variation in dosage, sources of information, beliefs, and approaches to the care of the envenomed patient.

Australian snakebite myotoxicity (ASP-23)

BACKGROUND

Myotoxicity is a recognised but poorly characterised effect of snake envenoming worldwide. We aimed to describe the clinical effects, complications and effectiveness of antivenom in myotoxicity from Australian snake envenoming.

METHODS

Patients were recruited to the Australian Snakebite Project (ASP), a prospective, observational study of patients with suspected or proven snakebite countrywide. After informed consent data is collected and stored in a dedicated database and blood samples are taken and stored. We included patients with envenoming and biochemical evidence of myotoxicity (peak creatine kinase [CK] > 1000 U/L). Snake species was determined by expert identification or venom specific enzyme immunoassay. Analysis included patient demographics, clinical findings, pathology results, treatment and outcomes (length of hospital stay, complications).

RESULTS

1638 patients were recruited January 2003-December 2016, 935 (57%) were envenomed, 148 developed myotoxicity (16%). Snake species most commonly associated with myotoxicity were Notechis spp. (30%), Pseudechis porphyriacus (20%) and Pseudechis australis (13%). Bite site effects occurred in 19 patients. Non-specific systemic symptoms occurred in 135 patients (91%), specific signs and symptoms in 83. In 120 patients with early serial CK results, the median peak CK was 3323 U/L (IQR;1050-785100U/L), the median time to first CK >500 U/L was 11.1 h and median time to peak CK of 34.3 h. White cell count was elevated in 136 patients (93%; median time to elevation, 4.9 h). 37 patients had elevated creatinine, six were dialysed. Two patients died from complications of severe myotoxicity. Antivenom given before the first abnormal CK (>500 U/L) was associated with less severe myotoxicity (2976 versus 7590 U/L). Non-envenomed patients with elevated CK had rapid rise to abnormal CK (median 3.5 h) and less had elevated WCC (32%).

CONCLUSION

Myotoxicity from Australian snakes is relatively common and has systemic effects, with significant associated morbidity and mortality. CK is not a good early biomarker of mytoxicity. Early antivenom may play a role in reducing severity.

Delayed antivenom for life-threatening tiger snake bite: Lessons learnt

An adolescent victim of an urban snakebite developed respiratory failure, rhabdomyolysis and consumption procoagulopathy but recovered with two vials of tiger snake antivenom administered after a delay of 48 hours. The clinical significance of a post-bite collapse was not initially appreciated. Tiger snake (Notechis spp.) venom antigen was measurable in blood before antivenom but not after whereas antivenom was measurable in blood for nine ensuing days. This case adds to growing evidence that further pharmacokinetic research of venom-antivenom interaction is required to establish the correct dose and timing of tiger snake antivenom. Antivenom therapy, even when delayed, facilitates recovery from snake envenomation.

Thrombotic microangiopathy and acute kidney injury following Sri Lankan Daboia russelii and Hypnale species envenoming

Context: Thrombotic microangiopathy (TMA) resulting in acute kidney injury (AKI) is an important complication of venomous snakebites. We aimed to describe TMA secondary to Russell's viper (Daboia russelli) and hump-nosed viper (Hypnale spp.) bites and assess the effect of different treatments.Materials and methods: We undertook a prospective observational study of patients with AKI secondary to snakebite over a two-year period. Data recorded included: demographic details, clinical and laboratory features, treatment, complications and outcomes, until hospital discharge and at three months post-discharge. TMA was defined as the development of microangiopathic hemolytic anemia and thrombocytopenia along with AKI. Treatment with therapeutic plasma exchange (TPE; also known as plasmapheresis) and/or fresh frozen plasma (FFP) was determined by the treating clinician. Antivenom was given to all patients with evidence of systemic envenoming following Russell's viper bites.Results: Fifty-nine patients were included in the analysis. Thirty-three (56%) were males and median age was 56 years. Forty-five (76%) developed TMA while a further 11 and two developed isolated thrombocytopenia and microangiopathic hemolytic anemia, respectively. Presence of TMA was associated with increased dialysis requirements (5 vs. 3) and longer hospital stay (18 vs. 12 days). Of the patients with TMA, nine received TPE with or without FFP infusions. The use of TPE was not associated with improved outcomes in patients with TMA based on requirement for blood transfusion, recovery of thrombocytopenia, requirement of dialysis and duration of hospital stay. Patients who did not receive TPE had better renal function at three months compared to patients who received this treatment.Conclusion: Presence of TMA in patients with Daboia and Hypnale bites was associated with a more prolonged course of AKI. Patients with TMA who were treated with TPE did not have improved early or late outcomes compared to patients who were not treated with TPE.

Coagulation factor activity patterns of venom-induced consumption coagulopathy in naturally occurring tiger snake (Notechis scutatus) envenomed dogs treated with antivenom

BACKGROUND

Venom-induced consumption coagulopathy (VICC) from tiger snake (Notechis scutatus) envenomation results in a dose-dependent coagulopathy that is detectable on coagulometry. However, individual coagulation factor activities in dogs with tiger snake envenomation have not been determined. This study aimed to characterise VICC and the time course of recovery in tiger snake envenomed dogs and to investigate an association between tiger snake venom (TSV) concentrations and factor activity.

METHODS

This was a prospective, observational, cohort study. The study cohort was 11 dogs of any age, breed, sex, body weight >10 kg, confirmed serum TSV on ELISA and treated with antivenom. Blood was collected at enrolment before antivenom administration, then at 3, 12 and 24 h after antivenom administration. Tiger snake venom concentrations were detected with a sandwich ELISA. Fibrinogen was measured using a modified Clauss method, and coagulation factors (F) II, V, VII, VIII and X were measured with factor-deficient human plasma using a modified prothrombin (PT) and activated partial thromboplastin (aPTT) method. Linear mixed models, with multiple imputations of censored observations, were used to determine the effect of time and TSV concentration on the coagulation times and factor activity. This cohort was compared to 20 healthy controls.

RESULTS

At enrolment, there were severe deficiencies in fibrinogen, FV and FVIII, with predicted recovery by 10.86, 11.75 and 13.14 h after antivenom, respectively. There were modest deficiencies in FX and FII, with predicted recovery by 20.57 and 32.49 h after antivenom, respectively. No changes were detected in FVII. Prothrombin time and aPTT were markedly prolonged with predicted recovery of aPTT by 12.58 h. Higher serum TSV concentrations were associated with greater deficiencies in FII, FV and FVIII, and greater prolongations in coagulation times. The median (range) serum TSV concentration was 57 (6-2295) ng/mL.

CONCLUSIONS

In tiger snake envenomed dogs, we detected a profound, TSV-concentration-related consumption of select coagulation factors, that rapidly recovered toward normal. These findings allowed further insight into tiger snake VICC in dogs.

Australian snake antivenom dosing: What is scientific and safe?

Because the median dose of one vial 'clears the blood of circulating venom', the authors of the Australian Snakebite Project recommend restriction of antivenom to one vial for all envenomated victims. This is neither scientific nor safe. Methodological flaws in the case series include limited detection of venom toxins and misinterpretation of data. The recommendation fails to consider larger doses of venom than that neutralised by one vial of antivenom. Although one vial may be adequate for minor envenomation, the initial dose should be two vials with more on a clinical basis.

Review article: Let us talk about snakebite management: A discussion on many levels

We want to discuss antivenom use in snakebite clinical practice guidelines. Coronial reviews in Victoria of two cases of snakebite envenomation, one described in detail below, prompted us to submit this paper for a wider audience and debate. Venom and antivenom levels were measured in the case detailed below, but not in the other. The coroner received conflicting and varied advice from experts regarding the dose of antivenom. The Victorian Department of Health and Human Services and the Australasian College for Emergency Medicine were instructed to review snakebite management guidelines, particularly with respect to antivenom dosage. The discussion that took place among medical experts led to considerable media attention. We discuss the potential fallout when there is no consensus among medical experts.

Long-term Effects of Snake Envenoming

Long-term effects of envenoming compromise the quality of life of the survivors of snakebite. We searched MEDLINE (from 1946) and EMBASE (from 1947) until October 2018 for clinical literature on the long-term effects of snake envenoming using different combinations of search terms. We classified conditions that last or appear more than six weeks following envenoming as long term or delayed effects of envenoming. Of 257 records identified, 51 articles describe the long-term effects of snake envenoming and were reviewed. Disability due to amputations, deformities, contracture formation, and chronic ulceration, rarely with malignant change, have resulted from local necrosis due to bites mainly from African and Asian cobras, and Central and South American Pit-vipers. Progression of acute kidney injury into chronic renal failure in Russell's viper bites has been reported in several studies from India and Sri Lanka. Neuromuscular toxicity does not appear to result in long-term effects. Endocrine anomalies such as delayed manifestation of hypopituitarism following Russell's viper bites have been reported. Delayed psychological effects such as depressive symptoms, post-traumatic stress disorder and somatisation have been reported. Blindness due to primary and secondary effects of venom is a serious, debilitating effect. In general, the available studies have linked a clinical effect to a snakebite in retrospect, hence lacked accurate snake authentication, details of acute management and baseline data and are unable to provide a detailed picture of clinical epidemiology of the long-term effects of envenoming. In the future, it will be important to follow cohorts of snakebite patients for a longer period of time to understand the true prevalence, severity, clinical progression and risk factors of long-term effects of snake envenoming.

An unusual case of gross myoglobinuria in a child following Russell's viper (Daboia russelii) envenomation

Overt myoglobinuria associated with myotoxicity is a classic feature of sea snake envenomation. Russell's viper bites usually result in coagulopathy, neurotoxicity and nephrotoxicity but rarely myotoxicity has been reported, especially in the Sri Lankan variety (Daboia russelii). All those studies have demonstrated mild degree myotoxicity with microscopic level myoglobinuria. We report what is probably the first case of gross myoglobinuria in a child following a Russell's viper bite with biochemical evidence of significant myotoxicity well beyond the levels that have been previously reported.

Defining the role of post-synaptic α-neurotoxins in paralysis due to snake envenoming in humans

Snake venom α-neurotoxins potently inhibit rodent nicotinic acetylcholine receptors (nAChRs), but their activity on human receptors and their role in human paralysis from snakebite remain unclear. We demonstrate that two short-chain α-neurotoxins (SαNTx) functionally inhibit human muscle-type nAChR, but are markedly more reversible than against rat receptors. In contrast, two long-chain α-neurotoxins (LαNTx) show no species differences in potency or reversibility. Mutant studies identified two key residues accounting for this. Proteomic and clinical data suggest that paralysis in human snakebites is not associated with SαNTx, but with LαNTx, such as in cobras. Neuromuscular blockade produced by both subclasses of α-neurotoxins was reversed by antivenom in rat nerve-muscle preparations, supporting its effectiveness in human post-synaptic paralysis.

Anti-Ophidian Properties of Herbal Medicinal Plants: Could it be a Remedy for Snake Bite Envenomation?

Snake bite envenoming causes high rates of morbidity and mortality and is one of the serious health-related concerns all over the globe. Around 3200 species of snakes have been discovered till date. Amid these species, about 1300 species of snakes are venomous. On account of its severity, World Health Organization (WHO) recently included snakebite envenoming in the list of neglected tropical diseases. Immunotherapy has partially solved the issues related to snakebite envenomation. However, it is associated with numerous adverse effects, due to which alternative treatment strategies are required for the treatment of snakebite. Traditionally, a large repository of herbal medicinal plants is known to possess activity against snake venom. An exploration of the therapeutic benefits of these medicinal plants used for the treatment of snakebites reveals the presence of various potential phytochemicals. The aim of the present review is to provide an outline regarding poisonous snakes all over the world, various compositions of snake venom, adverse effects related to anti-snake venom and numerous medicinal plants used for the anti-ophidian activity.

Spine-bellied sea snake (Hydrophis curtus) venom shows greater skeletal myotoxicity compared with cardiac myotoxicity

For the first time the impedance-based xCELLigence real-time cell analysis system was used to measure the myotoxicity of sea snake venom. With a focus on the spine-bellied sea snake (Hydrophis curtus), the venom of four sea snake species and three terrestrial snake species were compared for myotoxicity against a human skeletal muscle cell line (HSkMC). Hydrophis curtus venom was also tested on a human cardiac muscle cell line (HCM). Surprisingly, all four sea snake venoms tested on HSkMC produced an initial 100-280% rise in xCELLigence cell index that peaked within the first two hours before falling. The cell index rise of H. curtus venom was correlated with the WST-1 cell proliferation assay, which demonstrated an increase in mitochondrial metabolism. The myotoxicity of H. curtus was 4.7-8.2 fold less potent than the other sea snakes tested, the Australian beaked sea snake (Hydrophis zweifeli), the elegant sea snake (Hydrophis elegans) and the olive sea snake (Aipysurus laevis). If our cell-based results translate to H. curtus envenomations, this implies that H. curtus would be less myotoxic than the other three. Yet the myotoxicity of H. curtus venom to cardiac muscle cells was nine times weaker than for skeletal muscle cells, providing evidence that the venom has a selective effect on skeletal muscle cells. This evidence, combined with the slow-acting nature of the venom, supports a digestive role for sea snake myotoxins.

Australian elapid snake envenomation in cats: Clinical priorities and approach

Practical relevance: No fewer than 140 species of terrestrial snakes reside in Australia, 92 of which possess venom glands. With the exception of the brown tree snake, the venom-producing snakes belong to the family Elapidae. The venom of a number of elapid species is more toxic than that of the Indian cobra and eastern diamondback rattle snake, which has earned Australia its reputation for being home to the world's most venomous snakes. Clinical challenges: The diagnosis of elapid snake envenomation is not always easy. Identification of Australian snakes is not straightforward and there are no pathognomonic clinical signs. In cats, diagnosis of envenomation is confounded by the fact that, in most cases, there is a delay in seeking veterinary attention, probably because snake encounters are not usually witnessed by owners, and also because of the tendency of cats to hide and seek seclusion when unwell. Although the administration of antivenom is associated with improved outcomes, the snake venom detection kit and antivenom are expensive and so their use may be precluded if there are financial constraints. Evidence base: In providing comprehensive guidance on the diagnosis and treatment of Australian elapid snake envenomation in cats, the authors of this review draw on the published veterinary, medical and toxicology literature, as well as their professional experience as specialists in medicine, and emergency medicine and critical care.

Catch a tiger snake by its tail: Differential toxicity, co-factor dependence and antivenom efficacy in a procoagulant clade of Australian venomous snakes

A paradigm of venom research is adaptive evolution of toxins as part of a predator-prey chemical arms race. This study examined differential co-factor dependence, variations relative to dietary preference, and the impact upon relative neutralisation by antivenom of the procoagulant toxins in the venoms of a clade of Australian snakes. All genera were characterised by venoms rich in factor Xa which act upon endogenous prothrombin. Examination of toxin sequences revealed an extraordinary level of conservation, which indicates that adaptive evolution is not a feature of this toxin type. Consistent with this, the venoms did not display differences on the plasma of different taxa. Examination of the prothrombin target revealed endogenous blood proteins are under extreme negative selection pressure for diversification, this in turn puts a strong negative selection pressure upon the toxins as sequence diversification could result in a drift away from the target. Thus this study reveals that adaptive evolution is not a consistent feature in toxin evolution in cases where the target is under negative selection pressure for diversification. Consistent with this high level of toxin conservation, the antivenom showed extremely high-levels of cross-reactivity. There was however a strong statistical correlation between relative degree of phospholipid-dependence and clotting time, with the least dependent venoms producing faster clotting times than the other venoms even in the presence of phospholipid. The results of this study are not only of interest to evolutionary and ecological disciplines, but also have implications for clinical toxinology.

Elapid snake envenomation in horses: 52 cases (2006-2016)

BACKGROUND

Snake envenomation is a cause of morbidity and mortality in domestic animals worldwide. The clinical features of crotalid snake (pit viper) envenomation are widely reported and well described in horses but elapid snake envenomation is poorly characterised.

OBJECTIVES

To describe the presentation, clinical and laboratory findings, treatment and outcome of horses with a diagnosis of elapid snake envenomation in Australia.

STUDY DESIGN

Retrospective case series.

METHODS

Medical records of horses with a diagnosis of elapid snake envenomation (2006-2016) at several university and private veterinary practices were reviewed. Inclusion criteria comprised one or more of the following: 1) observed snakebite, 2) positive snake venom detection kit (SVDK) result, 3) appropriate clinical response to treatment with antivenom or 4) supportive post-mortem findings.

RESULTS

Fifty-two cases met the inclusion criteria. Most cases (94%) demonstrated clinical signs of neurotoxicity, characterised by generalised neuromuscular weakness. Associated neurologic signs included staggering gait, muscle fasciculations, recumbency, mydriasis, ptosis and tongue paresis. Concurrent clinically important conditions included rhabdomyolysis (50%) and haemolysis (19%). Of 18 urine samples evaluated with a SVDK, only three (17%) were positive. Overall survival was favourable (86%) among 49 horses who received antivenom. Eighteen surviving horses (43%) required more than one vial of antivenom.

MAIN LIMITATIONS

Possible cases within the searchable database were not included if horses died acutely or responded to symptomatic treatment without receiving antivenom.

CONCLUSIONS

Elapid snake envenomation is primarily a syndrome of neuromuscular weakness. Supportive anamnesis or an obvious bite site is rarely encountered. In endemic areas, this diagnosis should be considered for horses with generalised neuromuscular weakness, altered mentation, rhabdomyolysis and/or haemolysis; especially during spring and summer months. Diagnostic suspicion is best confirmed by response to treatment with antivenom.

The Australian Snakebite Project, 2005-2015 (ASP-20)

OBJECTIVE

To describe the epidemiology, treatment and adverse events after snakebite in Australia.

DESIGN

Prospective, multicentre study of data on patients with snakebites recruited to the Australian Snakebite Project (2005-2015) and data from the National Coronial Information System. Setting, participants: Patients presenting to Australian hospitals with suspected or confirmed snakebites from July 2005 to June 2015 and consenting to participation.

MAIN OUTCOME MEASURES

Demographic data, circumstances of bites, clinical effects of envenoming, results of laboratory investigations and snake venom detection kit (SVDK) testing, antivenom treatment and adverse reactions, time to discharge, deaths.

RESULTS

1548 patients with suspected snakebites were enrolled, including 835 envenomed patients (median, 87 per year), for 718 of which the snake type was definitively established, most frequently brown snakes (41%), tiger snakes (17%) and red-bellied black snakes (16%). Clinical effects included venom-induced consumption coagulopathy (73%), myotoxicity (17%), and acute kidney injury (12%); severe complications included cardiac arrest (25 cases; 2.9%) and major haemorrhage (13 cases; 1.6%). There were 23 deaths (median, two per year), attributed to brown (17), tiger (four) and unknown (two) snakes; ten followed out-of-hospital cardiac arrests and six followed intracranial haemorrhages. Of 597 SVDK test results for envenomed patients with confirmed snake type, 29 (4.9%) were incorrect; 133 of 364 SVDK test results for non-envenomed patients (36%) were false positives. 755 patients received antivenom, including 49 non-envenomed patients; 178 (24%), including ten non-envenomed patients, had systemic hypersensitivity reactions, of which 45 (6%) were severe (hypotension, hypoxaemia). Median total antivenom dose declined from four vials to one, but median time to first antivenom was unchanged (4.3 hours; IQR, 2.7-6.3 hours).

CONCLUSIONS

Snake envenoming is uncommon in Australia, but is often severe. SVDKs were unreliable for determining snake type. The median antivenom dose has declined without harming patients. Improved early diagnostic strategies are needed to reduce the frequently long delays before antivenom administration.

Antivenom for Neuromuscular Paralysis Resulting From Snake Envenoming

Antivenom therapy is currently the standard practice for treating neuromuscular dysfunction in snake envenoming. We reviewed the clinical and experimental evidence-base for the efficacy and effectiveness of antivenom in snakebite neurotoxicity. The main site of snake neurotoxins is the neuromuscular junction, and the majority are either: (1) pre-synaptic neurotoxins irreversibly damaging the presynaptic terminal; or (2) post-synaptic neurotoxins that bind to the nicotinic acetylcholine receptor. Pre-clinical tests of antivenom efficacy for neurotoxicity include rodent lethality tests, which are problematic, and in vitro pharmacological tests such as nerve-muscle preparation studies, that appear to provide more clinically meaningful information. We searched MEDLINE (from 1946) and EMBASE (from 1947) until March 2017 for clinical studies. The search yielded no randomised placebo-controlled trials of antivenom for neuromuscular dysfunction. There were several randomised and non-randomised comparative trials that compared two or more doses of the same or different antivenom, and numerous cohort studies and case reports. The majority of studies available had deficiencies including poor case definition, poor study design, small sample size or no objective measures of paralysis. A number of studies demonstrated the efficacy of antivenom in human envenoming by clearing circulating venom. Studies of snakes with primarily pre-synaptic neurotoxins, such as kraits (Bungarus spp.) and taipans (Oxyuranus spp.) suggest that antivenom does not reverse established neurotoxicity, but early administration may be associated with decreased severity or prevent neurotoxicity. Small studies of snakes with mainly post-synaptic neurotoxins, including some cobra species (Naja spp.), provide preliminary evidence that neurotoxicity may be reversed with antivenom, but placebo controlled studies with objective outcome measures are required to confirm this.

Clinical and Pharmacological Investigation of Myotoxicity in Sri Lankan Russell's Viper (Daboia russelii) Envenoming

BACKGROUND

Sri Lankan Russell's viper (Daboia russelii) envenoming is reported to cause myotoxicity and neurotoxicity, which are different to the effects of envenoming by most other populations of Russell's vipers. This study aimed to investigate evidence of myotoxicity in Russell's viper envenoming, response to antivenom and the toxins responsible for myotoxicity.

METHODOLOGY AND FINDINGS

Clinical features of myotoxicity were assessed in authenticated Russell's viper bite patients admitted to a Sri Lankan teaching hospital. Toxins were isolated using high-performance liquid chromatography. In-vitro myotoxicity of the venom and toxins was investigated in chick biventer nerve-muscle preparations. Of 245 enrolled patients, 177 (72.2%) had local myalgia and 173 (70.6%) had local muscle tenderness. Generalized myalgia and muscle tenderness were present in 35 (14.2%) and 29 (11.8%) patients, respectively. Thirty-seven patients had high (>300 U/l) serum creatine kinase (CK) concentrations in samples 24h post-bite (median: 666 U/l; maximum: 1066 U/l). Peak venom and 24h CK concentrations were not associated (Spearman's correlation; p = 0.48). The 24h CK concentrations differed in patients without myotoxicity (median 58 U/l), compared to those with local (137 U/l) and generalised signs/symptoms of myotoxicity (107 U/l; p = 0.049). Venom caused concentration-dependent inhibition of direct twitches in the chick biventer cervicis nerve-muscle preparation, without completely abolishing direct twitches after 3 h even at 80 μg/ml. Indian polyvalent antivenom did not prevent in-vitro myotoxicity at recommended concentrations. Two phospholipase A2 toxins with molecular weights of 13kDa, U1-viperitoxin-Dr1a (19.2% of venom) and U1-viperitoxin-Dr1b (22.7% of venom), concentration dependently inhibited direct twitches in the chick biventer cervicis nerve-muscle preparation. At 3 μM, U1-viperitoxin-Dr1a abolished twitches, while U1-viperitoxin-Dr1b caused 70% inhibition of twitch force after 3h. Removal of both toxins from whole venom resulted in no in-vitro myotoxicity.

CONCLUSION

The study shows that myotoxicity in Sri Lankan Russell's viper envenoming is mild and non-life threatening, and due to two PLA2 toxins with weak myotoxic properties.

Australian taipan (Oxyuranus spp.) envenoming: clinical effects and potential benefits of early antivenom therapy - Australian Snakebite Project (ASP-25)

CONTEXT

Taipans (Oxyuranus spp.) are medically important venomous snakes from Australia and Papua New Guinea. The objective of this study was to describe taipan envenoming in Australian and its response to antivenom.

METHODS

Confirmed taipan bites were recruited from the Australian Snakebite Project. Data were collected prospectively on all snakebites, including patient demographics, bite circumstances, clinical effects, laboratory results, complications and treatment. Blood samples were taken and analysed by venom specific immunoassay to confirm snake species and measure venom concentration pre- and post-antivenom.

RESULTS

There were 40 confirmed taipan bites: median age 41 years (2-85 years), 34 were males and 21 were snake handlers. Systemic envenoming occurred in 33 patients with neurotoxicity (26), complete venom induced consumption coagulopathy (VICC) (16), partial VICC (15), acute kidney injury (13), myotoxicity (11) and thrombocytopenia (7). Venom allergy occurred in seven patients, three of which had no evidence of envenoming and one died. Antivenom was given to 34 patients with a median initial dose of one vial (range 1-4), and a median total dose of two vials (range 1-9). A greater total antivenom dose was associated with VICC, neurotoxicity and acute kidney injury. Early antivenom administration was associated with a decreased frequency of neurotoxicity, acute kidney injury, myotoxicity and intubation. There was a shorter median time to discharge of 51 h (19-432 h) in patients given antivenom <4 h post-bite, compared to 175 h (27-1104 h) in those given antivenom >4 h. Median peak venom concentration in 25 patients with systemic envenoming and a sample available was 8.4 ng/L (1-3212 ng/L). No venom was detected in post-antivenom samples, including 20 patients given one vial initially and five patients bitten by inland taipans.

DISCUSSION

Australian taipan envenoming is characterised by neurotoxicity, myotoxicity, coagulopathy, acute kidney injury and thrombocytopenia. One vial of antivenom binds all measurable venom and early antivenom was associated with a favourable outcome.

A definite bite by the Ornamental Snake (Denisonia maculata) causing mild envenoming

CONTEXT

Many bites from mildly venomous elapids occur but identification or presence of systemic envenoming is rarely confirmed.

OBJECTIVE

To confirm systemic envenoming and binding of venom components to a commercial antivenom in a definite bite by the Ornamental Snake (Denisonia maculata) using enzyme immunoassays.

CASE

A 9-year old boy was bitten by an identified Ornamental Snake. He developed nausea, vomiting, local pain, and swelling. He had a leucocytosis (white cell count, 20.8 × 10(9)/L), an elevated international normalised ratio (INR) of 1.6, but otherwise normal blood tests including D-Dimer and activated partial thromboplastin time. He was treated with Australian Black Snake antivenom because the commercial venom detection kit was positive for Black snake. He was admitted for 36 h with continuing local pain and swelling requiring parenteral analgesia.

MATERIALS AND METHODS

Blood samples were collected with informed consent for measurement of venom and antivenom concentrations. Venom-specific enzyme immunoassays were developed using the closely related D. devisi venom with Rabbit anti-Notechis (Tiger Snake) and anti-Tropidechis (Rough-scaled Snake) IgG antibodies to detect venom in serum. Standard curves for measured venom versus actual venom concentrations were made to interpolate Denisonia venom concentrations. In vitro procoagulant and anticoagulant activity of venom was assayed.

RESULTS

Denisonia venom was detected in the pre-antivenom sample as 9.6 ng/mL D. devisi venom. No antigenic venom components were detected in post-antivenom samples and there were high antivenom concentrations. D. devisi venom had mild in vitro procoagulant activity with a minimum concentration required to clot after 5 min of 2.5-5 μg/mL and even weaker anticoagulant activity.

CONCLUSIONS

Denisonia bites appear to cause local effects and possibly mild systemic envenoming (with only non-specific systemic symptoms and leucocytosis), confirmed by detection of antigenic venom components in blood. A significant coagulopathy does not appear to occur.

Prospective assessment of the false positive rate of the Australian snake venom detection kit in healthy human samples

The Snake Venom Detection Kit (SVDK; bioCSL Pty Ltd, Australia) distinguishes venom from the five most medically significant snake immunotypes found in Australia. This study assesses the rate of false positives that, by definition, refers to a positive assay finding in a sample from someone who has not been bitten by a venomous snake. Control unbroken skin swabs, simulated bite swabs and urine specimens were collected from 61 healthy adult volunteers [33 males and 28 females] for assessment. In all controls, simulated bite site and urine samples [a total of 183 tests], the positive control well reacted strongly within one minute and no test wells reacted during the ten minute incubation period. However, in two urine tests, the negative control well gave a positive reaction (indicating an uninterpretable test). A 95% confidence interval for the false positive rate, on a per-patient rate, derived from the findings of this study, would extend from 0% to 6% and, on a per-test basis, it would be 0-2%. It appears to be a very low incidence (0-6%) of intrinsic true false positives for the SVDK. The clinical impresssion of a high SVDK false positive rate may be mostly related to operator error.

Incidence of serum sickness after the administration of Australian snake antivenom (ASP-22)

CONTEXT

Serum sickness is a delayed immune reaction resulting from the injection of foreign protein or serum. Antivenom is known to cause serum sickness but the incidence and characteristics are poorly defined.

OBJECTIVE

To investigate the incidence and clinical features of serum sickness following the administration of Australian snake antivenoms.

MATERIALS AND METHODS

This was a prospective cohort study of patients recruited to the Australian Snakebite Project who received snake antivenom from November 2012 to March 2014. Demographics, clinical information, laboratory tests and antivenom treatment were recorded prospectively. Patients administered antivenom were followed up at 7-10 days and 6 weeks' post-antivenom. The primary outcome was the proportion with serum sickness, pre-defined as three or more of: fever, erythematous rash/urticaria, myalgia/arthralgia, headache, malaise, nausea/vomiting 5-20 days post-antivenom.

RESULTS

During the 16-month period, 138 patients received antivenom. 23 were not followed up (unable to contact, tourist, child, bee sting) and 6 died in hospital. Of 109 patients followed up, the commonest reason for antivenom was venom induced consumption coagulopathy in 77 patients. An acute systemic hypersensitivity reaction occurred post-antivenom in 25 (23%) and 8 (7%) were severe with hypotension. Serum sickness occurred in 32/109 (29%) patients, including 15/37 (41%) given tiger snake, 6/15 (40%) given polyvalent and 4/23 (17%) given brown snake antivenom. There was no association between the volume of antivenom and serum sickness, p = 0.18. The commonest effects were lethargy, headache, muscle/joint aches and fever.

DISCUSSION

The incidence of serum sickness after snake antivenom in Australia was higher than earlier investigations which failed to define symptoms or follow-up patients, but similar to more recent studies of antivenoms in the United States.

CONCLUSION

Serum sickness is common with Australian snake antivenom but does not appear to be predictable based on the volume of antivenom administered.

An instructive case of presumed brown snake (Pseudonaja spp.) envenoming

CONTEXT

Several species of medically important Australian elapid snakes are frequently involved in human envenoming. The brown snake group (Pseudonaja spp., 9 species) is most commonly responsible for envenoming including life-threatening or fatal cases. Several Pseudonaja spp. can inflict human envenoming that features minor local effects, but may cause serious systemic venom disease including defibrination coagulopathy, thrombocytopenia, micro-angiopathic hemolytic anemia (MAHA) and, rarely, paralysis. Pseudonaja envenoming is typically diagnosed by history, clinical assessment including occasional active clinical bleeding noted on physical examination (e.g. from venipuncture sites, recent cuts, etc.), and laboratory detection of coagulopathy (prolonged activated partial thromboplastin time [APTT]/INR, elevated D-dimer, afibrinogenemia and thrombocytopenia). Lack of verified identity of the envenoming snake species is a common problem in Australia and elsewhere. Identification and confirmation of the envenoming Australian snake taxon is often attempted with enzyme sandwich immunoassay venom detection kits (SVDKs). However, the SVDK has limited utility due to unreliable specificity and sensitivity when used to detect venoms of some Australian elapids. Antivenom (AV) remains the cornerstone of treatment, although there is debate concerning the recommended dose (1 vs. 2 or more vials) necessary to treat serious Pseudonaja envenoming. Envenomed patients receiving timely treatment uncommonly succumb, but a proportion of seriously envenomed patients may exhibit clinical or laboratory evidence of myocardial insult.

CASE DETAILS

An 88-year-old woman presented her dog to a veterinarian after it had sustained a bite by a witnessed snake, reportedly an eastern brown snake (Pseudonaja textilis, Elapidae). The woman became suddenly confused, and lost consciousness at the veterinary office. After transport to hospital, she denied any contact with the snake, but developed large haematomas at intravenous (i.v.) catheter insertion sites; blood tests revealed a severe defibrination coagulopathy, consistent with envenoming by a brown snake. An SVDK-tested urine sample was negative. A non-contrast CT of her head showed a minor subacute infarction of the left corona radiata. A twelve-lead ECG was normal, but her troponins were mildly elevated (39 ng/L). A diagnosis of brown snake envenoming was made and she received 2 vials of brown snake AV i.v., without adverse incident. Thirty min post AV her Glasgow Coma Score (GCS) had improved from 13 to 15 (normal). At 3.5 h post AV all bleeding from i.v. sites ceased, although her troponin T level peaked at 639 ng/L, supporting a diagnosis of non-ST elevated myocardial infarction (NSTEMI).

DISCUSSION

Severe brown snake envenoming may occur in the absence of a perceived bite, and AV is temporally associated with improvement in clinical findings and coagulopathy. However, severe envenoming by this species can be complicated by cardiovascular events that in the circumstance of incomplete or absent history may confuse the primary diagnosis and affect patient outcome.

Snakebite in Australia: a practical approach to diagnosis and treatment

Snakebite is a potential medical emergency and must receive high-priority assessment and treatment, even in patients who initially appear well. Patients should be treated in hospitals with onsite laboratory facilities, appropriate antivenom stocks and a clinician capable of treating complications such as anaphylaxis. All patients with suspected snakebite should be admitted to a suitable clinical unit, such as an emergency short-stay unit, for at least 12 hours after the bite. Serial blood testing (activated partial thromboplastin time, international normalised ratio and creatine kinase level) and neurological examinations should be done for all patients. Most snakebites will not result in significant envenoming and do not require antivenom. Antivenom should be administered as soon as there is evidence of envenoming. Evidence of systemic envenoming includes venom-induced consumption coagulopathy, sudden collapse, myotoxicity, neurotoxicity, thrombotic microangiopathy and renal impairment. Venomous snake groups each cause a characteristic clinical syndrome, which can be used in combination with local geographical distribution information to determine the probable snake involved and appropriate antivenom to use. The Snake Venom Detection Kit may assist in regions where the range of possible snakes is too broad to allow the use of monovalent antivenoms. When the snake identification remains unclear, two monovalent antivenoms (eg, brown snake and tiger snake antivenom) that cover possible snakes, or a polyvalent antivenom, can be used. One vial of the relevant antivenom is sufficient to bind all circulating venom. However, recovery may be delayed as many clinical and laboratory effects of venom are not immediately reversible. For expert advice on envenoming, contact the National Poisons Information Centre on 13 11 26.

Clinical predictors of acute kidney injury following snake bite envenomation

Background:

Snake bite envenomation is a major public health concern in developing countries. Acute kidney injury (AKI) is as important cause of mortality in patients with vasculotoxic snake bite.

Aims:

This study was to evaluate the clinical profile of snake bite patients and to determine the predictors of developing AKI following snake bite.

Materials and Methods:

Two hundred and eighty-one patients with snake envenomation were included. Eighty-seven patients developed AKI (Group A) and 194 (Group B) did not. History, examination findings and investigations results were recorded and compared between the two groups.

Results:

In group A, 61 (70.11%) patients were male and in group B, 117 (60.30%) patients were male. Out of 281 patients, 232 had cellulitis, 113 had bleeding tendencies, 87 had oliguria, 76 had neuroparalysis, and 23 had hypotension at presentation. After multivariate analysis, bite to hospital time (P = 0.016), hypotension (P = 0.000), albuminuria (P = 0.000), bleeding time (P = 0.000), prothrombin time (P = 0.000), hemoglobin (P = 0.000) and total bilirubin (P = 0.010) were significant independent predictors of AKI.

Conclusions:

AKI developed in 30.96% of patients with snake bite, leading to mortality in 39.08% patients. Factors associated with AKI are bite to hospital time, hypotension, albuminuria, prolonged bleeding time, prolonged prothrombin time, low hemoglobin and a high total bilirubin.

Detection of venom-antivenom (VAV) immunocomplexes in vitro as a measure of antivenom efficacy

The measurement of free venom with enzyme immunoassay in serum of patients with snake envenoming is used to confirm snake identification and to determine if sufficient antivenom has been given. Recent studies with Russell's viper (RV; Daboia russelii) envenoming have detected free venom post-antivenom despite recovery of coagulopathy. This raises the question as to whether this assay also measures venom-antivenom (VAV) complexes. In this study we developed an assay to measure VAV complexes and investigate the binding of venom and antivenom in vitro. The assay consisted of rabbit anti-snake venom IgG attached to a microplate which binds the venom component of VAV and anti-horse IgG antibodies conjugated to horseradish peroxidase to detect the antivenom portion of VAV. A known amount of venom or toxin was incubated with increasing antivenom concentrations and VAV was detected as absorbance at 450 nm and plotted against AV concentration. Pseudonaja textilis (brown snake), Notechis scutatus (tiger snake), Oxyuranus scutellatus (taipan), Tropidechis carinatus (rough-scaled snake), Pseudechis porphyriacus (red-bellied black snake) and D. russelii mixtures with appropriate antivenoms were assayed. Measured VAV initially increased with increasing antivenom concentration until it reached a maximum after which the VAV concentration decreased with further increasing antivenom concentrations. The VAV curves for two Australian snake venom-antivenom mixtures, Hoplocephalus stephensii and Ancanthophis antarcticus, had broad VAV peaks with two maxima. Two fractions isolated from N. scutatus venom and Russell's viper factor X activator toxin produced similar VAV curves to their whole venoms. The antivenom concentration for which the maximum VAV occurred was linearly related to the venom concentration, and this slope or ratio was consistent with that used to define the neutralisation units for Australian antivenoms. The maximal VAV point appears to represent the antivenom concentration where every venom molecule (toxin) is attached to at least one antivenom molecule (antibody) on average and may be a useful measure of antivenom efficacy. In vivo this would mean that for a defined antivenom concentration, venom components will be eliminated and are trapped in the central compartment.

Neurotoxicity in snakebite--the limits of our knowledge

Snakebite is classified by the WHO as a neglected tropical disease. Envenoming is a significant public health problem in tropical and subtropical regions. Neurotoxicity is a key feature of some envenomings, and there are many unanswered questions regarding this manifestation. Acute neuromuscular weakness with respiratory involvement is the most clinically important neurotoxic effect. Data is limited on the many other acute neurotoxic manifestations, and especially delayed neurotoxicity. Symptom evolution and recovery, patterns of weakness, respiratory involvement, and response to antivenom and acetyl cholinesterase inhibitors are variable, and seem to depend on the snake species, type of neurotoxicity, and geographical variations. Recent data have challenged the traditional concepts of neurotoxicity in snake envenoming, and highlight the rich diversity of snake neurotoxins. A uniform system of classification of the pattern of neuromuscular weakness and models for predicting type of toxicity and development of respiratory weakness are still lacking, and would greatly aid clinical decision making and future research. This review attempts to update the reader on the current state of knowledge regarding this important issue.

An examination of cardiovascular collapse induced by eastern brown snake (Pseudonaja textilis) venom

The Pseudonaja genus (Brown snakes) is widely distributed across Australia and bites account for significant mortality. Venom-induced consumption coagulopathy (VICC) and, less often, early cardiovascular collapse occur following envenoming by these snakes. We have previously examined possible mechanism(s) behind the early cardiovascular collapse following Papuan taipan (Oxyuranus scutellatus) envenoming. In the present study, we investigate early cardiovascular collapse in anaesthetized rats following administration of eastern brown snake (Pseudonaja textilis) venom, and prevention of this effect with prior administration of 'priming' doses (i.e. doses of venom which caused a transient hypotensive response) of venom. P. textilis venom (5-10 μg/kg, i.v.) induced cardiovascular collapse in anaesthetized rats, characterized by a rapid decrease in systolic blood pressure until non recordable. Prior administration of 'priming' doses of P. textilis venom (2 and 3 μg/kg) or, at least, 4-5 doses of O. scutellatus (2 μg/kg, i.v.) or Daboia russelii limitis (20 μg/kg, i.v.) venoms prevented cardiovascular collapse induced by P. textilis venom. Moreover, early collapse was also inhibited by prior administration of 2 discrete doses of Acanthophis rugosus venom. Prior administration of commercial polyvalent snake antivenom (500-3000 units/kg, i.v.) or heparin (300 units/kg, i.v.) also inhibited P. textilis venom-induced cardiovascular collapse. Our results indicate that P. textilis venom-induced cardiovascular collapse can be prevented by prior administration of sub-lethal doses of venom from P. textilis, O. scutellatus, A. rugosus and D. russelii limitis. This suggests that sudden cardiovascular collapse following envenoming is likely to involve a common mechanism/pathway activated by different snake venoms.

A randomized controlled trial of fresh frozen plasma for treating venom-induced consumption coagulopathy in cases of Australian snakebite (ASP-18)

BACKGROUND

Venom-induced consumption coagulopathy (VICC) is a major effect of snake envenoming.

OBJECTIVES

To investigate whether fresh frozen plasma (FFP) given after antivenom resulted in more rapid correction of coagulation.

PATIENTS/METHODS

This was a multicenter open-label randomized controlled trial in patients with VICC of FFP vs. no FFP within 4 h of antivenom administration. Patients (> 2 years) recruited to the Australian snakebite project with VICC (International Normalized Ratio [INR] > 3) were eligible. Patients were randomized 2 : 1 to receive FFP or no FFP. The primary outcome was the proportion with an INR of < 2 at 6 h after antivenom administration. Secondary outcomes included time from antivenom administration to discharge, adverse effects, major hemorrhage, and death.

RESULTS

Of 70 eligible patients, 65 consented to be randomized: 41 to FFP, and 24 to no FFP. Six hours after antivenom administration, more patients randomized to FFP had an INR of < 2 (30/41 [73%] vs. 6/24 [25%]; absolute difference, 48%; 95% confidence interval 23-73%; P = 0.0002). The median time from antivenom administration to discharge was similar (34 h, range 14-230 h vs. 39 h, range 14-321 h; P = 0.44). Seven patients developed systemic hypersensitivity reactions after antivenom administration - two mild and one severe (FFP arm), and three mild and one severe (no FFP). One serious adverse event (intracranial hemorrhage and death) occurred in an FFP patient with pre-existing hypertension, who was hypertensive on admission, and developed a headache 6 h after FFP administration. Post hoc analysis showed that the median time from bite to FFP administration was significantly shorter for non-responders to FFP than for responders (4.7 h, interquartile range [IQR] 4.2-6.7 h vs. 7.3 h, IQR 6.1-8 h; P = 0.002).

CONCLUSIONS

FFP administration after antivenom administration results in more rapid restoration of clotting function in most patients, but no decrease in discharge time. Early FFP administration (< 6-8 h) post-bite is less likely to be effective.

Mulga snake (Pseudechis australis) envenoming: a spectrum of myotoxicity, anticoagulant coagulopathy, haemolysis and the role of early antivenom therapy - Australian Snakebite Project (ASP-19)

CONTEXT

Mulga snakes (Pseudechis australis) are venomous snakes with a wide distribution in Australia. Objective. The objective of this study was to describe mulga snake envenoming and the response of envenoming to antivenom therapy.

MATERIALS AND METHODS

Definite mulga bites, based on expert identification or venom-specific enzyme immunoassay, were recruited from the Australian Snakebite Project. Demographics, information about the bite, clinical effects, laboratory investigations and antivenom treatment are recorded for all patients. Blood samples are collected to measure the serum venom concentrations pre- and post-antivenom therapy using enzyme immunoassay.

RESULTS

There were 17 patients with definite mulga snake bites. The median age was 37 years (6-70 years); 16 were male and six were snake handlers. Thirteen patients had systemic envenoming with non-specific systemic symptoms (11), anticoagulant coagulopathy (10), myotoxicity (7) and haemolysis (6). Antivenom was given to ten patients; the median dose was one vial (range, one-three vials). Three patients had systemic hypersensitivity reactions post-antivenom. Antivenom reversed the coagulopathy in all cases. Antivenom appeared to prevent myotoxicity in three patients with high venom concentrations, given antivenom within 2 h of the bite. Median peak venom concentration in 12 envenomed patients with samples was 29 ng/mL (range, 0.6-624 ng/mL). There was a good correlation between venom concentrations and the area under the curve of the creatine kinase for patients receiving antivenom after 2 h. Higher venom concentrations were also associated with coagulopathy and haemolysis. Venom was not detected after antivenom administration except in one patient who had a venom concentration of 8.3 ng/ml after one vial of antivenom, but immediate reversal of the coagulopathy.

DISCUSSION

Mulga snake envenoming is characterised by myotoxicity, anticoagulant coagulopathy and haemolysis, and has a spectrum of toxicity that is venom dose dependant. This study supports a dose of one vial of antivenom, given as soon as a systemic envenoming is identified, rather than waiting for the development of myotoxicity.

Effect of Australian elapid venoms on blood coagulation: Australian Snakebite Project (ASP-17)

Snake venoms contain toxins that activate the coagulation network and cause venom-induced consumption coagulopathy. A previously developed mathematical model of the coagulation network was refined and used to describe and predict the time course of changes in the coagulation factors following envenomation by Brown snake (Pseudonaja spp.), Tiger snake (Notechis scutatus), Rough-scaled snake (Tropidechis carinatus) and Hoplocephalus spp. (Stephens banded, Pale headed and Broad headed). Simulations of the time course of the change in coagulation factors were compared to data obtained from a large prospective study of Australian snake bites - the Australian Snakebite Project. The model predictions were also compared against data for partial and complete VICC obtained from the same study. The model simulations were used to understand the differences in consumption and recovery of clotting factors in partial versus complete VICC as well as among bites from different snake types. The model suggested that the venoms were absorbed almost instantaneously and provided a reasonable prediction of the observed concentration of clotting factors over time in patients bitten by Australian elapid snakes. The model predictions suggested a higher consumption of factors (fibrinogen, II and IX in particular) in patients with complete VICC compared to those with partial VICC. The model also predicted that snakes with "Xa-like" venoms may produce a less severe VICC than snakes with "Xa:Va-like" venoms.