Spider bites of medical significance in the Mediterranean area: misdiagnosis, clinical features and management

Abstract

Despite the disrepute spiders have had for centuries, their bite is a rare occurrence. In the Mediterranean area, only two of the numerous known species are considered of medical significance: Latrodectus tredecimguttatus and Loxosceles rufescens. Spider bites have no pathognomonic signs or symptoms, therefore most diagnoses are presumptive; a spider bite can only be diagnosed when a spider (seen at the time of the bite) is collected and identified by an expert, since most physicians and patients are unable to recognize a certain spider species or distinguish spiders from other arthropods. Skin lesions of uncertain etiology are too often attributed to spider bites. In most cases, these are actually skin and soft-tissue infections, allergic reactions, dermatoses etc. Misdiagnosing a wound as a spider bite can lead to delays in appropriate care, cause adverse or even fatal outcomes and have medical-legal implications. Concerningly, misinformation on spider bites also affects the medical literature and it appears there is lack of awareness on current therapeutic indications for verified bites.

Spider bites in France: Epidaemiology of cases occurring in 10 years in metropolitan France

“…The clinical presentation reported for the patients was characterized by intense pain at the bite site, associated with local signs: oedema with visible skin punctures, possibly pruritus and paraesthesias in the bitten area. These signs correspond with those usually reported in the literature (Fusto et al, 2020; Varl et al, 2017). General signs (headache, hyperthermia) have been reported for 10%–20% of cases for which spider identification was uncertain (Vetter et al, 2006).…”

“…One bite out of five occurred in the Provence‐Alpes‐Côte d'Azur region, which corresponds to the distribution area of this spider. It can be found near or even inside houses, where it finds a suitable temperature all year round (Fusto et al, 2020; Nentwig et al, 2017). Although it is not a particularly aggressive spider, it can bite when it feels threatened or is accidentally pressed against the human skin, which can happen during the night when the patient turns over in their sheets or when they put on their clothes (Mullen & Vetter, 2019).…”

“…These species are big spiders (up to 8 cm), which can raise questions in individuals who observe them, motivating frequent requests for information from the PCC of Marseille (personal communication). The bite seemed to be painful rather because of the skin effraction allowed by powerful chelicerae, even if the venom is cytotoxic and likely to cause compressive oedema (De Haro et al, 1997; Fusto et al, 2020; Mullen & Vetter, 2019).…”

“…It can bite to defend itself or when the female wants to protect its eggs. In a study of spider bites in Switzerland, it was the species most frequently involved in human cases (Fusto et al, 2020). The patients reported bites that were not very painful, although, as in our study, an extensive local reaction may occur (Bertlich et al, 2019).…”

Report of cutaneous loxoscelism caused by violin spider bite in Northern Italy

“…Among the few species of spiders considered of medical significance, whose bite may have severe complications, only two spider species can be found in the Mediterranean area: Latrodectus tredecimguttatus (known as Mediterranean black widow) and Loxosceles rufescens (known as violin spider), which is native to Europe but has been spread worldwide 4 . We showed the patient photos of the two spiders most likely responsible for the injury, and he recognized with sufficient certainty that it was a bite of a violin spider.…”