Clinical effects and treatment of envenoming by Hoplocephalus spp. snakes in Australia: Australian Snakebite Project (ASP-12)

Abstract

There is limited information on envenoming by snakes of the genus Hoplocephalus from Eastern Australia. We investigated the clinical and laboratory features of patients with definite Hoplocephalus spp. bites including antivenom treatment, recruited to the Australian Snakebite Project. There were 15 definite Hoplocephalus spp. bites based on expert identification including eight by Hoplocephalus stephensi (Stephen's banded snakes), four by Hoplocephalus bungaroides (broad-headed snake) and three by H. bitorquatus (pale-headed snake). Envenoming occurred in 13 patients and was similar for the three species with venom induced consumption coagulopathy (VICC) in all envenomings. Seven patients had an INR >12 and partial VICC, with only incomplete fibrinogen consumption, occurred in three patients. Systemic symptoms occurred in eight patients. Myotoxicity and neurotoxicity did not occur. H. stephensi venom was detected in all three H. stephensi envenomings (1.1, 44 and 81 ng/mL) for whom pre-antivenom blood samples were available, and not detected in one without envenoming. In two cases with post-antivenom blood samples, venom was not detected after tiger snake antivenom (TSAV) was given. In vitro binding studies demonstrated that TSAV concentrations of 50mU/mL are sufficient to bind the majority of free H. stephensi venom components at concentrations above those detected in envenomed patients (100 ng/mL). Eleven patients received antivenom, median dose 2 vials (Range: 1 to 5 vials), which was TSAV in all but one case, where polyvalent antivenom was used. Immediate hypersensitivity reactions occurred in six cases including one case of anaphylaxis. Envenoming by Hoplocephalus spp. causes VICC and systemic symptoms, making it clinically similar to brown snake (Pseudonaja spp.) envenoming. Based on in vitro studies reported here, patients may be treated with one vial of TSAV, although one vial of brown snake antivenom may also be sufficient.