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

Abstract

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.

Keywords:

• Mulga snake
• Pseudechis australis
• Envenoming
• Antivenom
• Myotoxicity
• Coagulopathy
• Haemolysis
• Black snake
• Venom

Acknowledgments

On behalf of the ASP clinical investigators who recruited patients to the study, including Peter Garrett, Paul Negus (Nambour Hospital), Sam Alfred (Royal Adelaide Hospital), and Naren Gunja (Westmead Hospital). We acknowledge the many referrals from the National Poison Centre Network and clinical toxicologists and the help of the many other nurses, doctors and laboratory staff in recruiting patients and collecting samples. We thank Renai Kearney for data entry and follow-up of patient information and medical records.

Declaration of interest

The study was supported by NHMRC Project Grant ID490305. GKI is supported by an NHMRC Clinical Career Development Award ID605817. SGAB is supported by NHMRC Career Development Fellowship Award ID1023265.

The authors report no declarations of interest. The authors alone are responsible for the content and writing of the paper.