Objective: To investigate species-specific envenoming rates and spectrum of severity of funnel-web spider bites, and the efficacy and adverse effects of funnel-web spider antivenom.
Data sources: Cases were identified from a prospective study of spider bite presenting to four major hospitals and three state poisons information centres (1999-2003); museum records of spider specimens since 1926; NSW Poisons Information Centre database; MEDLINE and EMBASE search; clinical toxinology textbooks; the media; and the manufacturer's reports of antivenom use.
Data extraction: Patient age and sex, geographical location, month, expert identification of the spider, clinical effects and management; envenoming was classified as severe, mild-moderate or minor/local effects.
Data synthesis: 198 potential funnel-web spider bites were identified: 138 were definite (spider expertly identified to species or genus), and 77 produced severe envenoming. All species-identified severe cases were attributed to one of six species restricted to NSW and southern Queensland. Rates of severe envenoming were: Hadronyche cerberea (75%), H. formidabilis (63%), Atrax robustus (17%), Hadronyche sp. 14 (17%), H. infensa (14%) and H. versuta (11%). Antivenom was used in 75 patients, including 22 children (median dose, 3 ampoules; range, 1-17), with a complete response in 97% of expertly identified cases. Three adverse reactions were reported, all in adults: two early allergic reactions (one mild and one with severe systemic effects requiring adrenaline), and one case of serum sickness.
Conclusions: Severe funnel-web spider envenoming is confined to NSW and southern Queensland; tree-dwelling funnel webs (H. cerberea and H. formidabilis) have the highest envenoming rates. Funnel-web spider antivenom appears effective and safe; severe allergic reactions are uncommon.