Detection of Loxosceles species venom in dermal lesions: a comparison of 4 venom recovery methods

Loxosceles species spider envenomations may produce necrotic, disfiguring dermal inflammatory lesions resembling neutrophilic dermatoses. With definitive treatment options lacking, clinicians are reluctant to obtain invasive biopsy specimens for diagnostic analysis. We compared less invasive venom collection methods and determined the time limit after inoculation for feasible venom recovery in an animal model.

Nine New Zealand rabbits were randomized to 1 of 3 groups (n=3). Groups 1 and 2 were inoculated intradermally with 3 microg of L reclusa venom at 5 inoculation sites per rabbit. Albumin (3 microg) was injected intradermally in each rabbit as a negative control. Hair (group 1) and aspirate samples (group 2) were collected (1 time per site) over a 1-week period after inoculation. Group 3 was inoculated with 3 microg of Loxosceles species venom on 1 flank and 3 microg of albumin on the opposite flank. Daily serum specimens were collected over a 7-day period. On day 7, dermal punch biopsy specimens were taken from the venom and control inoculation sites. Hair, aspirate, biopsy, and serum specimens were assayed for venom by using an enzyme-linked immunosorbent assay. A generalized linear model was fit with the generalized estimating equation method to estimate the mean differences between groups.

Venom was detected in hair, aspirate, and biopsy specimens on all days of the study period. Hair samples yielded venom recovery on day 1 (median 0.062 ng/100 microL; mean difference 0.054 ng/100 microL; 95% confidence interval [CI] 0.048 to 0.059) through day 7 (median 0.020 ng/100 microL; mean difference 0.020 ng/100 microL; 95% CI 0.013 to 0.027). Aspirates were positive for venom recovery on day 1 (median 0.275 ng/100 microL; mean difference 0.231 ng/100 microL; 95% CI 0.192 to 0.271) through day 7 (median 0.0 ng/100 microL; mean difference 0.032 ng/100 microL; 95% CI -0.18 to 0.078). The highest venom yield was from the biopsy specimens (median 1.75 ng/100 microL; mean difference 0.041 ng/100 microL; 95% CI 0.033 to 0.027). Venom was undetectable in all serum samples.

Loxosceles species venom is detectable in hair, aspirate, and dermal biopsy specimens at least 7 days after venom inoculation and undetectable in serum by using the rabbit model.