Envenoming and antivenom use in Australia.

Australia has a diverse and rich venomous fauna, both terrestrial and marine, including some of the most venomous species in each class. Antivenom is the principal therapy for the majority of medically significant envenomings and is currently supplied through a single source, CSL, Melbourne. Cases of envenoming reported to Australian poisons information centers (PICs) are dominated by spiderbite and insect stings, respectively accounting for 53.7% and 39.3% of all bite/sting calls. Marine animal bites/stings/poisonings account for only 4% of PIC calls in this category, while snakebites account for a mere 3% (still at least 400 calls/yr). Because most PIC calls are from the public, not doctors/hospitals, snakebite in particular is under-represented. The author has recently reviewed antivenom usage in Australia. Snakebite affects between 1,000 to 3,000 people per year, with an average annual mortality of about 2 cases. Brown snakes (genus Pseudonaja) cause the majority of deaths (and bites), with tiger snakes (genus Notechis) and taipans (genus Oxyuranus) accounting for nearly all other fatalities. Up to 500 cases require snake antivenoms each year, the majority of cases coming from rural areas of Queensland, Western Australia, New South Wales and Victoria, these being the most populated states. The wide availability of snake venom detection kits has allowed specific antivenom to be used more often, rather than polyvalent antivenom, but the latter is still used in nearly 30% of cases, suggesting underutilization of venom detection. The issue of premedication prior to antivenom remains unresolved. Antivenom usage and complication data for 1995 and 1996 will be presented. Red back spider antivenom is the most commonly used antivenom, with reports of usage being greater than for all other antivenoms combined. It is reported as being therapeutically efficacious in 94% of cases, with a single ampoule being used in 76% of cases, 2 ampoules in 18% of cases, and 3 or more ampoules in 6% of cases. Clinical experience suggests only 20% of red back spider bites require antivenom therapy. It is likely that between 5-10,000 bites occur annually.