A new assay for the detection of Loxosceles species (brown recluse) spider venom

Study Objective:Dermal lesions from unrelated arthropod species and medical causes appear similar to Loxoscelesspecies (brown recluse spider) bites. This may result in delayed diagnosis and treatment. We developed a sensitive Loxoscelesspecies venom enzyme-linked immunosorbent assay (ELISA) and characterized the specificity of the assay by evaluating antigenic cross-reactivity from a variety of North American arthropod venoms. Methods:North American arthropod (14 spiders, 2 scorpions, and 1 bee) venoms were studied. Three venom amounts (diluted in 100 μL of ELISA buffer) were assayed: 16,000 ng, 2,000 ng, and 40 ng. The latter quantity was selected because this is the observed maximum amount of venom we detect when inoculating dermis with amounts likely to be deposited by a spider bite. The larger venom amounts are overwhelming quantities designed to test the limits of the assay for arthropod venom cross-reactivity. Similar amounts of Loxoscelesspecies venom and bovine albumin served as positive and negative controls, respectively. Results:At the lowest amount of venom tested (40 ng), the ELISA detected only the Loxoscelesspecies positive control. When 2,000 ng was assayed, only Scytodes fuscaand Kukulcania hibernalisarachnid venoms (in addition to Loxosceles species) cross-reacted to the assay. Finally, at 16,000 ng, the ELISA assay modestly detected Diguetia canities, Heteropoda venatoria, Tegenaria agrestis, Plectreurys tristes, Dolomedes tenebrosus, and Hadrurus arizonensisarachnid venoms. Conclusion: Cross-reactivity was observed in 8 of 17 North American arthropod venoms when large venom amounts were assayed with a Loxoscelesspecies ELISA. By using a relevant quantity of venom, 40 ng, the assay was specific for Loxoscelesspecies venom. The venom specificity of the ELISA may allow clinical application in Loxoscelesspecies endemic regions of North America. [Gomez HF, Krywko DM, Stoecker WV. A new assay for the detection of Loxoscelesspecies (brown recluse) spider venom. Ann Emerg Med.May 2002;39:469-474.]