Not as docile as it looks? Loxosceles venom variation and loxoscelism in the Mediterranean Basin and the Canary Islands

Abstract

The medical importance of Loxosceles spiders has promoted extensive research on different aspects of their venoms. Most of the reported cases of loxoscelism have occurred in the Americas, and thus, much work has focused on North and South American Loxosceles species. Interestingly, loxoscelism cases are rare in the Mediterranean Basin although Loxosceles rufescens, endemic to the Mediterranean, is an abundant spider even in human-altered areas. Thus, it has been suggested that the venom of L. rufescens could be of less medical relevance than that of its congeners. In this study, we challenge this hypothesis by using multiple approaches to study venom variation in selected species and lineages from the Mediterranean Basin and the Canary Islands. We found that SMase D activity, the key bioactive component of Loxosceles venom, is comparable to American species that are confirmed to have medically relevant bites. The venom protein composition using SDS-PAGE presents some differences among regional Loxosceles taxa in banding pattern and intensity, mostly between the Canarian and L. rufescens lineages. Differences between these species also exist in the expression of different paralogs of the SicTox gene family, with the Canarian species being less diverse. In conclusion, our results do not support the challenged hypothesis, and suggest that venom of these species may indeed be as potent as other Loxosceles species. Pending confirmation of loxoscelism with direct evidence of Loxosceles bites with species identification by professionals, Loxosceles in the Mediterranean region should conservatively be considered medically relevant taxa.

Rare case of dermonecrosis caused by a recluse spider bite in Europe

“…Different species are endemic to each continent. A MEDLINE search of the word ‘Recluse spider’ revealed several case reports of Loxosceles reclusa bites in North and South America, but few from the Mediterranean where L. rufescens is the culprit species 4. These case reports were documented in Italy, Spain, Portugal, France, Turkey, Greece and Israel 1 5–13 .…”

“…Furthermore, various case reports have shown that L. rufescens tends to cause milder symptoms compared to the more infamous L. reclusa . The latter may be arguable since recent in vitro and animal studies on the venom from L. rufescens has shown it to be of similar strength to that from other species such as L. reclusa 422…”

Cutaneous loxoscelism due to Loxosceles rufescens

“…[1][2][3][4][5][6][8][9][10] We offer the second case in our country of cutaneous loxoscelism with correct identification of L. rufescens. As recently noted by Planas et al,11 this species should also be taken into account as a possible agent of this clinical presentation. Treatment of resistant port-wine stains with bosentan and pulsed dye laser: a pilot prospective study Editor Pulsed dye laser (PDL) is the gold standard treatment port-wine stains (PWS) but provides inconsistent results.…”

Dangerous arachnids—Fake news or reality?

“…Phospholipase D is present and active in the venoms of different Hexophthalma, Loxosceles and Sicarius species and it can cause haemolysis and keratinocyte cell death (Lopes et al, 2013;Planas et al, 2015;Magalhaes et al, 2017). Medically relevant incidents are mostly…”