Venom Detection Kit Research Articles

Immunoreactivity of eastern small eyed snake (Cryptophis nigrescens) venom towards species-specific antibodies of five medically important venomous Australian elapids.

The eastern small eyed snake (Cryptophis nigrescens; CN) is an uncommon cause of snakebite in Australia despite the widespread distribution of the snake along the east coast of Australia. Diagnosis of envenomation relies on identification of the snake which is often not possible with animal snakebite cases. This study examined the immunoreactivity profile of CN venom towards specific rabbit IgG made against the medically relevant snake venom immunotypes found in Australia (tiger, brown, black, death adder and taipan). A simultaneous sandwich ELISA format was used to quantify CN venom binding to venom specific Protein A purified rabbit IgG. The binding profiles demonstrated weak binding of CN venom to rabbit IgG made against both tiger (N. scutatus) and black snake (P. australis) venoms with approximately 0.19% and 0.069% cross reactivity, respectively. However, the concentration of venom likely to be present in the urine of CN envenomed patients and the low cross reactivity suggest that envenomed veterinary patients are unlikely to be detected in the commercial snake venom detection kit. It is possible that CN envenomation is more common but may be underdiagnosed where snake venom antigen detection is relied upon solely. Serum biochemical abnormalities also overlap with other snake species found in the same geographical area. In respect of antivenom therapy, administration of tiger snake antivenom is supported by the binding data, but due to the low cross reactivity multiple vials may be required. Limited clinical evidence also supports the efficacy of tiger snake antivenom for envenomation by CN.

Prototyping of a lateral flow assay based on monoclonal antibodies for detection of Bothrops venoms

BackgroundBrazil is home to a multitude of venomous snakes; perhaps the most medically relevant of which belong to the Bothrops genus. Bothrops spp. are responsible for roughly 70% of all snakebites in Brazil, and envenomings caused by their bites can be treated with three types of antivenom: bothropic antivenom, bothro-lachetic antivenom, and bothro-crotalic antivenom. The choice to administer antivenom depends on the severity of the envenoming, while the choice of antivenom depends on availability and on how certain the treating physician is that the patient was bitten by a bothropic snake. The diagnosis of a bothropic envenoming can be made based on expert identification of the dead snake or a photo thereof or based on a syndromic approach wherein the clinician examines the patient for characteristic manifestations of envenoming. This approach can be very effective but requires staff that has been trained in clinical snakebite management, which, unfortunately, far from all relevant staff has. ResultsIn this article, we describe a prototype of the first lateral flow assay (LFA) capable of detecting venoms from Brazilian Bothrops spp. The monoclonal antibodies for the assay were generated using hybridoma technology and screened in sandwich enzyme-linked immunosorbent assays (ELISAs) to identify Bothrops spp.-specific antibody sandwich pairs. The prototype LFA is able to detect venom from several Bothrops spp. The LFA has a limit of detection (LoD) of 9.5 ng/mL in urine, when read with a commercial reader, and a visual LoD of approximately 25 ng/mL. SignificanceThe work presented here serves as a proof of concept for a genus-specific venom detection kit that could support physicians in diagnosing Bothrops envenomings. Although further optimisation and testing is needed before the LFA can find clinical use, such a device could aid in decentralising antivenoms in the Brazilian Amazon and help ensure optimal snakebite management for even more victims of this highly neglected disease.

Pathology of Fatal Australian Black Snake (Pseudechis sp) Envenomation in Two Adult Dogs

Black snakes (Pseudechis spp) are a genus of venomous Australian elapid snakes that can cause major clinical envenomation in companion animals, which may be fatal, even with appropriate antivenom treatment. Despite its clinical significance, there is little published information on the pathology of black snake envenomation. We report the gross and microscopic lesions associated with black snake envenomation in two dogs, one with a definitive immunological species identification of red-bellied black snake (RBBS; Pseudechis porphyriacus), the other with a black snake immunotype on a venom detection kit. Both dogs were located in a geographical area where the RBBS is found. The prominent gross findings in both cases included icterus, localized facial oedema in the region of the presumed bite wound, pigmenturia and multicavitary serosanguineous effusions. Histopathology of the confirmed RBBS case revealed acute renal tubular necrosis with haemosiderosis, marked splenic haemosiderosis and centrilobular to midzonal hepatocellular necrosis with severe cholestasis. Defining the spectrum of lesions of elapid snake envenomation improves understanding of the pathogenesis, which may lead to improved patient outcomes and post-mortem diagnosis.

Diagnosis and Treatment of Snake Envenomation in Dogs in Queensland, Australia.

Australia has some of the most venous snakes in the world, and envenomations of domestic dogs are common, but clinical signs as well as the diagnostic procedures and treatments of snake envenomations are poorly described. Therefore, we invited veterinary clinics in the state of Queensland, Australia, to provide detailed data on snake envenomation cases in dogs. A total of 230 cases were reported from 19 veterinary hospitals, with an average of 12.1 dogs per clinic, per year. Detailed case data were provided from 20 dogs—of these, 65.0% (13/20) were envenomated during the daytime, with collapse and paresis being the most common signs reported by owners. The median time between the onset of clinical signs and admission to the veterinary hospital was 60 min. Clinical signs were the sole diagnostic modality utilised by veterinarians in 30.0% (6/20) of cases. Activated clotting time was the most common diagnostic procedure conducted, while snake venom detection kits (SVDK) were only used in 15.0% (3/20) of cases. Of the dogs that received antivenom (85.0%, 17/20), the tiger/multibrown combination (3000 units tiger/4000 units brown) was predominately (13/17) provided. Three of the 17 dogs that received antivenom (17.6%) died or were euthanised. About 82.4% (14/17) of the dogs treated with antivenom, but only 33.3% (1/3) of the dogs not treated with antivenom, recovered (p = 0.140). Overall, veterinarians relied frequently on medical history, clinical signs, and diagnostic tests other than the SVDK and, thus, most likely, administered snake envenomation treatment based on their clinical experience.

Collocation of avian and mammal antibodies to develop a rapid and sensitive diagnostic tool for Russell's Vipers Snakebite.

Russell’s vipers (RVs) envenoming is an important public health issue in South-East Asia. Disseminated intravascular coagulopathy, systemic bleeding, hemolysis, and acute renal injury are obvious problems that develop in most cases, and neuromuscular junction blocks are an additional problem caused by western RV snakebite. The complex presentations usually are an obstacle to early diagnosis and antivenom administration. Here, we tried to produce highly specific antibodies in goose yolks for use in a paper-based microfluidic diagnostic kit, immunochromatographic test of viper (ICT-Viper), to distinguish RVs from other vipers and even cobra snakebite in Asia. We used indirect ELISA to monitor specific goose IgY production and western blotting to illustrate the interaction of avian or mammal antibody with venom proteins. The ICT-Viper was tested not only in prepared samples but also in stored patient serum to demonstrate its preliminary efficacy. The results revealed that specific anti-Daboia russelii IgY could be raised in goose eggs effectively without inducing adverse effects. When it was collocated with horse anti-Daboia siamensis antibody, which broadly reacted with most of the venom proteins of both types of Russell’s viper, the false cross-reactivity was reduced, and the test showed good performance. The limit of detection was reduced to 10 ng/ml in vitro, and the test showed good detection ability in clinical snake envenoming case samples. The ICT-Viper performed well and could be combined with a cobra venom detection kit (ICT-Cobra) to create a multiple detection strip (ICT-VC), which broadens its applications while maintaining its detection ability for snake envenomation identification. Nonetheless, the use of the ICT-Viper in the South-East Asia region is pending additional laboratory and field investigations and regional collaboration. We believe that the development of this practical diagnostic tool marks the beginning of positive efforts to face the global snakebite issue.

A Rapid and International Applicable Diagnostic Device for Cobra (Genus Naja) Snakebites.

Cobra snakes (genus Naja) are some of the most dangerous snake species in Asia and Africa, as their bites cause severe life-threatening respiratory failure and local tissue destruction, especially in the case of late diagnosis. The differential diagnosis of snakebite envenomation still mainly relies upon symptomatology, the patient’s description, and the experience of physicians. We have designed a rapid test, immunochromatographic test of cobra (ICT-Cobra), which obtained fair results in improving the diagnosis and treatment of Naja (N.) atra snakebites in Taiwan. In this study, we further investigated the feasibility of applying the kit for the detection of other cobra venoms based on the potential interspecies similarity. We firstly demonstrated the cross-reactivity between eight venoms of medically important cobra species and the rabbit anti-N. atra IgG that was used in ICT-Cobra by Western blotting and sandwich enzyme-linked immunosorbent assay. Then, ICT-Cobra was used to detect various concentrations of the eight venoms to elucidate its performance. Noticeable correlations between the cross-reactivity of venoms from genus Naja snakes and existing geographical characteristics were found. ICT-Cobra could detect venoms from other Asian cobras with variable detection limits comparable to those observed for N. atra, but the kit was less successful in the detection of venom from African cobras. The similar but slightly different venom components and the interaction between venom and rabbit anti-N. atra IgG led to variations in the detection limits. The transcontinental usage of ICT-Cobra might be possible due to the cross-reactivity of antibodies and similarities among the larger-sized proteins. This study showed that the close immunological relationships in the genus Naja could be used to develop a venom detection kit for the diagnosis of cobra envenomation in both Asian and African regions. Additional clinical studies and technical adjustments are still needed to improve the efficacy and broadening the application of ICT-Cobra in the future.

SnakeMap: four years of experience with a national small animal snake envenomation registry.

SnakeMap is a national cloud-based, veterinary snakebite registry. It was designed to prospectively collect data of the clinical circumstances and temporospatial information on cases of snake envenomation in dogs and cats. We herein introduce the project and summarise the data from the first 4 years of SnakeMap. The registry is a veterinary community-based online database allowing case entry from veterinary hospitals across Australia. Registry data comprise hospital characteristics, patient characteristics, envenoming snake type, treatment and outcome variables, including time and geolocation of the snake bite. We present summative information on select key variables from the SnakeMap registry (1 July 2015 to 30 June 2019). Twenty-eight hospitals from 6 states/territories entered 624 cases into the registry, including 419 dogs (67%) and 205 cats (33%). Bite time was available in 216 animals of which 90 (42%) were reported to be bitten in the 3 hours between 03:00 pm and 05:59 pm; median bite to presentation interval was 60 (interquartile range [IQR] 30, 211) minutes in dogs and 95 (IQR 41, 238) minutes in cats. Bites occurred in the owner's yard in 356 dogs (85%) and 53 cats (26%). A snake venom detection kit was used in 172 cases (28%) and antivenom was administered in 523 cases (85%). Most animals (n = 534, 88%) survived to discharge (median hospitalisation of 25 [IQR 16, 62] hours). SnakeMap effectively collects relevant clinical data from dogs and cats with presumed snake bite and provides locally specific information on the epidemiology of snake envenomation in small animals.

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.

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

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. To describe the presentation, clinical and laboratory findings, treatment and outcome of horses with a diagnosis of elapid snake envenomation in Australia. Retrospective case series. 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. 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. Possible cases within the searchable database were not included if horses died acutely or responded to symptomatic treatment without receiving antivenom. 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).

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

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 × 109/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.

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.

The Australian mulga snake (Pseudechis australis: Elapidae): Report of a large case series of bites and review of current knowledge

BackgroundThe mulga snake (Pseudechis australis) is the largest terrestrial venomous snake in Australia. It is capable of inflicting severe and occasionally fatal envenoming, but there have been few studies of P. australis bites. ObjectivesTo highlight and reinforce the main features of P. australis envenoming and to provide a clearer picture of the epidemiology of bites from this species. MethodsSelected case records kept by the Toxinology Dept. (Women's and Children's Hospital, Adelaide, Australia) were reviewed retrospectively to determine definite P. australis bites. Inclusion criteria: definite cases where the snake was identified by a competent person and/or lab specimens (bite site/urine) tested positive for “black snake” using CSL snake venom detection kit in a locality within the known range of P. australis, but without sympatry with other Pseudechis spp. Exclusion criteria: where the snake could not be clearly identified under criteria above. Epidemiological and clinical information was recorded and analysed for the definite cases. ResultsA total of 27 cases were identified as definite P. australis bites; there were no fatalities. The median age was 35.5 years (IQR 51-23) and 80% of bites occurred in males. More bites occurred in the warmer months (Dec–March) and in those handling/interfering with snakes. Seven people were bitten whilst asleep at night. 21/27 patients developed systemic envenoming (based on signs, symptoms and laboratory results) and 17 cases received antivenom. Local bite site pain (18) and swelling (17) were common as were non-specific generalised symptoms such as nausea, vomiting and headache. Myotoxicity (11) and anticoagulant coagulopathy (10) occurred frequently; haemolysis was seen in fewer cases (3). Two patients developed local tissue injury around the bite site requiring further treatment. ConclusionsThis study confirms previous reports about P. australis bites with respect to high rates of envenoming, commonly associated with pain and swelling and systemic effects of rhabdomyolysis and anticoagulant coagulopathy. Systemic envenoming, even severe cases, responds well to antivenom therapy. Compared to other Australian snakes, a high proportion of bites occur in people asleep at night. Medically significant local tissue injury around the bite site may occur and may be associated with inappropriate first-aid, particularly the vascular occlusive type.

Snake bite poisoning: A neglected life-threatening occupational hazard

Snake bite poisoning: A neglected life-threatening occupational hazard

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.

In this issue - September 2013

In this issue - September 2013

Point-of-care testing in snakebite: An envenomed case with false negative coagulation studies

Early detection of venom-induced consumption coagulopathy (VICC) in Australian snake bite is important for early antivenom administration.1 However, many patients present to smaller or rural hospitals where on-site laboratory coagulations studies are not available. Point-of-care (POC) devices for an international normalised ratio (INR) and d-dimer have become available and have been used in this setting. A 43-year-old woman presented to a small rural hospital in southwest Western Australia an hour after being bitten while putting her hand in a fish pond. She immediately saw ‘blood on her knuckle’, felt unwell with nausea and vomited twice, experienced chest tightness and felt faint. She did not apply first aid and washed the bite site. She was well on arrival to hospital, with no bleeding, no ptosis and normal vital signs. An INR was performed with a POC device (AlereTM INRatio2, Alere San Diego, San Diego, CA, USA), which was 1.3 on admission and 1.5 half an hour later. A pressure bandage was applied and she was transferred to a regional base hospital. On arrival at the base hospital 4 h post-bite the patient felt better and the INR was 0.9 on a second POC device (RocheTM CoaguChek, Roche Diagnostics, Mannheim, Germany). Blood collected at the same time was sent to the on-site laboratory where the INR was unrecordable. On examination there was oozing from the venipuncture site and no neurotoxicity. A snake venom detection kit was positive for tiger snake venom on urine. Two vials of tiger snake antivenom were given and the patient enrolled in the Australian Snakebite Project (ASP) randomised controlled trial of fresh frozen plasma (FFP).2 The patient was randomised to receive 4 units of FFP given immediately after antivenom. Additional serum and citrate samples were collected for ASP. A d-dimer performed on a POC device (RocheTM Cobas H232, Roche Diagnostics Limited, Rotkreuz, Switzerland) was 0.38 mg/L (<0.36). The patient had no immediate adverse reaction to antivenom or FFP and had an uneventful recovery, being discharged on day 3. Serial INR results are shown in Figure 1. Serial d-dimers done on the POC device ranged from 0.24 to 0.73 mg/L. The creatine kinase peaked at 432 IU/L. On follow up, the patient had symptoms consistent with mild serum sickness. Time-course of the laboratory compared with the international normalised ratio (INR) derived from the point-of-care (POC) testing devices. (), Laboratory INR; (), POC INR. Tiger snake venom (Notechis spp.) was detected at a concentration of 5.1 ng/mL in serum prior to antivenom and was undetectable post-antivenom. Repeat coagulation studies on admission gave an INR >12, activated partial thromboplastin time (aPTT) >180 s, undetectable fibrinogen and a d-dimer of 812 mg/L (<0.25). At 9 h post-bite, the INR was 2.2, aPTT was 39.5 s, fibrinogen was 0.4 g/L and d-dimer was 458 mg/L. The POC testing results for the INR and d-dimer were incorrect and misleading in this patient with tiger snake envenoming. This might have resulted in delayed treatment if the patient had not been transferred to a hospital equipped for laboratory confirmation of the INR. In addition to identifying problems with POC testing in VICC, the case underlines the importance of the history of a suspected snake bite and early systemic symptoms in the patient. Misleading POC INR results have been reported previously with laboratory-confirmed severe VICC.3, 4 This suggests that POC testing for INR and D-dimer are likely to be unreliable in VICC and formal laboratory testing is recommended until POC testing devices are formally assessed in VICC. Patients with suspected snakebite should be managed in hospitals with laboratory-based INR and aPTT testing available, or be transferred to a larger hospital. It remains unclear whether this problem applies to all POC testing systems. Currently, no other bedside clotting test is available, including the 20 min whole blood clotting test, which has also been shown to be unreliable,5 and glass tubes are not readily available in Australia. There is an urgent need for a rapid bedside clotting test for VICC. The study was supported in part by a National Health and Medical Research Council (NHMRC) Project Grant (ID490305). GKI is supported by a NHMRC Clinical Career Development Award (ID605817). None declared.

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

OBJECTIVES: To describe the clinical syndrome associated with definite tiger snake (Notechis spp) envenoming and to examine the ability of tiger snake antivenom (TSAV) to bind free venom in vivo. DESIGN, SETTING AND PARTICIPANTS: We conducted a prospective cohort study within the Australian Snakebite Project, reviewing all definite tiger snake envenoming cases between October 2004 and June 2011. Definite cases were identified by venom-specific enzyme immunoassay or expert snake identification. MAIN OUTCOME MEASURES: Clinical effects of tiger snake envenoming; peak venom concentrations; number of vials of antivenom administered. RESULTS: Fifty-six definite tiger snake envenomings were identified. Clinical effects included venom-induced consumption coagulopathy (VICC) (n = 53), systemic symptoms (n = 45), myotoxicity (n = 11) and neurotoxicity (n = 17). Thrombotic microangiopathy occurred in three patients, all of whom developed acute renal failure. There were no deaths. A bite-site snake venom detection kit test was done in 44 patients, but was positive for tiger snake in only 33 cases. Fifty-three patients received TSAV and eight of these patients had immediate hypersensitivity reactions, severe enough in one case to satisfy diagnostic criteria for severe anaphylaxis. The median peak venom concentration in 50 patients with pretreatment blood samples available was 3.2 ng/mL (interquartile range [IQR], 1-12 ng/mL; range 0.17-152 ng/mL). In 49 patients with post-treatment blood samples available, no venom was detected in serum after the first antivenom dose. Ten patients were given 1 vial of TSAV; the median dose was 2 vials (range, 1-4 vials). Pretreatment serum venom concentrations did not vary significantly between patients given 1 vial of TSAV and those given 2 or more vials. CONCLUSION: Tiger snake envenoming causes VICC, systemic symptoms, neurotoxicity and myotoxicity. One vial of TSAV, the dose originally recommended when the antivenom was first made available, appears to be sufficient to bind all circulating venom. Language: en

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

To describe the clinical syndrome associated with definite tiger snake (Notechis spp) envenoming and to examine the ability of tiger snake antivenom (TSAV) to bind free venom in vivo. We conducted a prospective cohort study within the Australian Snakebite Project, reviewing all definite tiger snake envenoming cases between October 2004 and June 2011. Definite cases were identified by venom-specific enzyme immunoassay or expert snake identification. Clinical effects of tiger snake envenoming; peak venom concentrations; number of vials of antivenom administered. Fifty-six definite tiger snake envenomings were identified. Clinical effects included venom-induced consumption coagulopathy (VICC) (n = 53), systemic symptoms (n = 45), myotoxicity (n = 11) and neurotoxicity (n = 17). Thrombotic microangiopathy occurred in three patients, all of whom developed acute renal failure. There were no deaths. A bite-site snake venom detection kit test was done in 44 patients, but was positive for tiger snake in only 33 cases. Fifty-three patients received TSAV and eight of these patients had immediate hypersensitivity reactions, severe enough in one case to satisfy diagnostic criteria for severe anaphylaxis. The median peak venom concentration in 50 patients with pretreatment blood samples available was 3.2 ng/mL (interquartile range [IQR], 1-12 ng/mL; range 0.17-152 ng/mL). In 49 patients with post-treatment blood samples available, no venom was detected in serum after the first antivenom dose. Ten patients were given 1 vial of TSAV; the median dose was 2 vials (range, 1-4 vials). Pretreatment serum venom concentrations did not vary significantly between patients given 1 vial of TSAV and those given 2 or more vials. Tiger snake envenoming causes VICC, systemic symptoms, neurotoxicity and myotoxicity. One vial of TSAV, the dose originally recommended when the antivenom was first made available, appears to be sufficient to bind all circulating venom.