http://nova.newcastle.edu.au/vital/access/services/Feed ${session.getAttribute("locale")} 5 http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:10950 Objective: To describe the clinical features and laboratory findings in patients with definite red-bellied black snake (RBBS; Pseudechis porphyriacus) bites, including correlation with results of venom assays. Design, patients and setting: Prospective cohort study of patients with definite RBBS bites, recruited to the Australian Snakebite Project from January 2002 to June 2010. Main outcome measures: Clinical and laboratory features of envenoming; peak venom concentrations and antivenom treatment. Results: There were 81 definite RBBS bites; systemic envenoming occurred in 57 patients (70%) and local envenoming alone occurred in one patient. Systemic envenoming was characterised by local envenoming in 55 patients (96%), systemic symptoms in 54 patients (95%), anticoagulant coagulopathy with a raised activated partial thromboplastin time (aPTT) in 35 patients (61%) and myotoxicity in seven patients (12%). One patient required non-invasive ventilation for severe myotoxicity that resulted in muscle weakness. Three patients developed local ulceration. There were no deaths. Twenty-two envenomed patients (39%) received tiger snake or black snake antivenom, and administration within 6 hours of the bite was associated with normalisation of the aPTT. Eight patients (36%) had immediate hypersensitivity reactions to antivenom, including one case of anaphylaxis. The median peak venom concentration in 37 systemically envenomed patients with serum available was 19ng/mL (interquartile range, 12-50 ng/mL; range, 3-360ng/mL), which did not correlate with clinical severity. In 17 patients who received antivenom and had venom concentration measured, no venom was detected in serum after the first antivenom dose, including nine who were given one vial of tiger snake antivenom. Conclusion: RBBS envenoming caused local effects, systemic symptoms, anticoagulant coagulopathy and, uncommonly, myotoxicity. One vial of tiger snake or black snake antivenom appears to be sufficient to remove venom and neutralise reversible effects, but hypersensitivity reactions occurred in over a third of patients. 2012-06-22T05:59:53.203Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:10701 Assessment of the procoagulant effect of snake venoms is important for understanding their effects. The aim of this study was to develop a simple automated method to measure clotting times to assess procoagulant venoms. A turbidimetric assay was developed which monitors changes in optical density when plasma and venom are mixed. Plasma was added simultaneously to venom solutions in a 96 well microtitre plate. After mixing, the optical density at 340 nm was monitored in a microplate reader every 30 s over 30 min. The clotting time was defined as the lag time until the absorbance sharply increased. The turbidimetric method was compared to manual measurement of the clotting time defined as the time when a strand of fibrin can be drawn out of the mixture. The two methods were done simultaneously, with the same venom and plasma, and compared by plotting the manual versus turbidimetric clotting times. Within-day and between-day runs were done and the coefficient of variation (CV) was calculated. Plots comparing manual clotting times to the lag time in the turbidimetric assay showed good correlation between the two methods for brown snake (Pseudonaja textilis) venom, including 24 determinations in triplicate over six days for seven different venom concentrations. Good correlation was also found for four other venoms: tiger snake (Notechis scutatus), Carpet viper (Echis carinatus), Russell's viper (Daboia russelii) and Malaysian pit piper (Calloselasma rhodostoma). Between-day CV was in the range 10–20% for both methods, while within-day CV < 10%. The turbidimetric assay appears to be a simple and convenient automated method for the measurement of clotting times to assess the effects of procoagulant venoms. 2012-04-24T05:57:30.362Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:10032 An understanding of the cross-neutralisation of snake venoms by antibodies is important for snake antivenom development. We investigated the cross-neutralisation of brown snake (Pseudonaja textilis) venom, taipan (Oxyuranus scutellatus) venom and death adder (Acanthophis antarcticus) with commercial antivenoms and monovalent anti-snake IgG, using enzyme immunoassays, in vitro clotting and neurotoxicity assays. Each commercial antivenom bound all three venoms, and neutralised clotting activity of brown snake and taipan venoms and neurotoxicity of death adder venom. The ‘in-house’ monovalent anti-snake venom IgG raised against procoagulant brown snake and taipan venoms, did not neutralise the neurotoxic effects of death adder venom. However, they did cross-neutralise the procoagulant effects of both procoagulant venoms. This supports the idea of developing antivenoms against groups of snake toxins rather than individual snake venoms. 2012-02-10T04:00:03.644Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:10030 We report a 60 year old male bitten by snakes from the Acanthophis genus (Death adder) on two occasions who developed high titres of human IgG antibodies to Acanthophis venom detected at the time of the second bite. The patient was bitten by Acanthophis antarcticus (common death adder) on the first occasion, developed non-specific systemic effects and did not receive antivenom. Three months later he was bitten by Acanthophis praelongus (northern death adder) and he developed significant local myotoxicity associated with a moderate rise in the creatine kinase (maximum 4770 U/L). He was given antivenom 55 h after the bite and recovered over several days. Death adder venom was detected in serum at the time of the first bite, but not the second bite. Human IgG antibodies to death adder were detected on the second admission but not the first. However, despite the presence of antibodies to death adder venom and free venom not being detected, the patient still developed significant local myotoxicity. 2012-02-10T03:50:03.757Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:10024 Venom-induced consumption coagulopathy occurs in snake envenoming worldwide but the interaction between procoagulant snake venoms and human coagulation remains poorly understood. We aimed to evaluate an assay using endogenous thrombin potential (ETP) to investigate the procoagulant properties of a range of Australian whole venoms in human plasma and compared this to traditional clotting and prothrombinase activity studies. We developed a novel modification of ETP using procoagulant snake venoms to trigger thrombin production. This was used to characterise the relative potency, calcium and clotting factor requirements of five important Australian snake venoms and efficacy of commercial antivenom, and compared this to prothrombinase activity and clotting assays. All five venoms initiated thrombin generation in the absence and presence of calcium. Pseudonaja textilis (Brown snake; p < 0.0001), Hoplocephalus stephensii (Stephen’s-banded snake; p < 0.0001) and Notechis scutatus (tiger snake; p = 0.0073) all had statistically significant increases in ETP with calcium. Venom potency varied between assays, with ETP ranging from least potent with Oxyuranus scutellatus (Taipan) venom to intermediate with N. scutatus and H. stephensii venoms to most potent with P. textilis and Tropidechis carinatus (Rough-scale snake) venoms. ETPs for N. scutatus, T. carinatus and H. stephensii venoms were severely reduced with factor V deficient plasma. Antivenom neutralized the thrombin generating capacity but not prothrombin substrate cleaving ability of the venoms. Contrary to previous studies using clotting tests and factor Xa substrates, these venoms differ in calcium requirement. ETP is a useful assay to investigate mechanisms of other procoagulant venoms and is a robust method of assessing antivenom efficacy. 2012-02-10T02:50:06.649Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:7323 Monovalent antivenoms have a lower volume of specific antibodies that may reduce reactions but require accurate snake identification to be used. Polyvalent antivenoms are larger volume and may have a higher reaction rate. However, they avoid the problem of snake identification and may be more cost-effective to manufacture. We have previously shown cross-neutralisation of two Australian elapid venoms, tiger snake (Notechis scutatus) and brown snake (Pseudonaja textilis) venoms, by their respective monovalent antivenoms. In this study enzyme immunoassays were used to quantify the amount of monovalent antivenom (quantity of monovalent antibodies to a specific snake venom) in vials of commercially produced antivenom in Australia. All antivenoms tested appeared to be polyvalent and contain varying amounts of all five terrestrial snake monovalent antibodies based on their binding to the five representative venoms. Redback spider antivenom did not have any measurable binding affinity for any of the five snake venoms, showing that the observed binding is not due to non-specific interactions with equine protein. The antivenoms had expiry dates over a 15 year period, suggesting that the antivenoms have been mixtures for at least this time. This study cannot be used to rationalise hospital stocks of antivenom in Australia because there is no guarantee that the antivenoms will remain as mixtures. However, it would be possible for the manufacturer toreduce the number of types of snake antivenoms available in Australia to two polyvalent antivenoms which would simplify treatment of snakebite. 2011-03-01T01:10:09.142Z ]]>