A prospective study of definite bites by spiders of the family Sparassidae (huntsmen spiders) with identification to species level.

Spiders of the family Sparassidae occur on most continents in tropical and temperate regions of the world. They are large Araneomorphae (modern spiders) which are often feared. There are few reports of confirmed sparassid bites and some suggest that particular genera (Neosparassus) can cause severe effects. This study investigated the circumstances and clinical effects of bites by Australian sparassid spiders with correlation to taxonomic species level. Cases were recruited prospectively from calls to Australian poison information centres and two emergency departments. Patients were included if there was a clear history of bite and the spider was caught, and were followed up over a week. There were 173 patients with spider injuries and 168 with definite bites by sparassid spiders over a 27 month period. Ninety-five percent of bites were by spiders from four genera: Isopeda (32%), Isopedella (21%), Neosparassus (27%) and Heteropoda (14%); other genera included Delena and Holconia. The seasonal and diurnal distribution of bites differed between genera, although the majority occurred in warmer months in daylight hours. Seventy-six percent of bites occurred because the spider was interfered with (picked up, dressing or picked up an object with the spider) consistent with the behaviour of most of the family requiring provocation to bite. Ninety-five percent of bites occurred on limbs, 82% on distal limbs, again consistent with handling the spider. Pain/discomfort occurred in all cases, and was severe in 27%. The median duration of pain was 5 min which was significantly less than other spiders. Puncture marks (40%) or localised initial bleeding (35%) occurred in 54% of bites, and both occurred significantly more often in all sparassid bites compared to all other spider bites (p<0.0001). Swelling occurred in 16%, itchiness in 14% and redness/red mark in 57% of cases, the latter significantly less common than other spiders (p=0.0002). Systemic effects occurred in 4% of bites and were minor (nausea and/or headache). There were no cases of necrotic ulcers or allergic reactions. There were four cases with features consistent with local infection. Bites by sparassid spiders cause minor effects, characterised by immediate and transient pain, associated with bleeding, puncture marks and local redness. The mechanism of effects appeared to be trauma rather than envenoming. There were no major differences between genera, and Neosparassus spp. did not cause major effects.