Histopathological findings in rabbits after experimental acute exposure to the Loxosceles intermedia (brown spider) venom

Abstract

Summary. Loxoscelism, the term used to describe envenomation with brown spiders, is characterized by a dermonecrotic lesion at the bite site. In the present investigation we submitted albino rabbits to an acute experimental envenomation protocol using Loxosceles intermedia (brown spider) venom, with in order to determine the pathogenesic features of the lesion induced by this spider, which is the cause of several accidents throughout the world. Rabbits received intradermal injections of the venom and were monitored over the first 4 h, and then at 12 h and 1, 2 and 5 days after envenomation. Histological specimens from 3 rabbits per time point were collected from euthanized animals and processed for histological examination by light microscopy. Major findings observed during the first 4 h were oedema, haemorrhage, degeneration of blood vessel walls, plasma exudation, thrombosis, neutrophil accumulation in and around blood vessels with an intensive diapedesis, a diffuse collection of inflammatory cells (polymorphonuclear leucocytes) in the dermis, and subcutaneous muscular oedema. Over the following hours and up to 5 days after envenomation the changes progressed to massive neutrophil infiltration (with no other leucocytes) into the dermis and even into subcutaneous muscle tissue, destruction of blood vessels, thrombosis, haemorrhage, myonecrosis, and coagulative necrosis on the 5th day.

Histopathological characterization of experimentally induced cutaneous loxoscelism in rabbits inoculated with Loxosceles similis venom

“…The present results are similar to those of Rattmann et al (30) using L. intermedia venom in rat experimental model. According to our data, the inflammation increases progressively from two hours and then becomes severe eight hours post L. similis crude venom injection corroborating the already existing studies with L. laeta and L. intermedia venom (15,17,32). Morphometrical parameters showed here can be used to monitor the process dynamics, and also any treatment and sera effectiveness studies (22,31,33,34).…”

“…The edema was intense and thrombosis was observed as early as two hours after injection. These lesions are similar to those observed for other medically important species of Loxosceles (13)(14)(15).…”

“…Histopathological studies with three Loxosceles species of clinical importance, L. intermedia, L. laeta and L. recluse, showed that the venom induces vasodilation, edema, inflammatory infiltrate (mainly neutrophilic), hemorrhage, cutaneous muscle necrosis, thrombosis and arteriolar walls degeneration (6,(13)(14)(15). It is necessary to elucidate whether the histological lesion induced by the Loxosceles similis venom is similar to that observed in other species of medical importance.…”

Necrotic skin lesion in a dog attributed to Loxosceles (brown spider) bite: a case report

“…In the current work, skin biopsy demonstrated necrotic process along with edema and inflammatory infiltrate, essentially neutrophilic, and such necrosis was described as dermoepidermal compatible with loxoscelism. Similar findings were reported five days after experimental inoculation of the venom in rabbits (28).…”

Management of Brown Recluse Spider Bites in Primary Care

“…6 Histological examination reveals a mixed inflammatory cell infiltrate, coagulative tissue necrosis, and vasculitis. 7,8 The complement system may be inactivated. 9 The response persists until the toxin is lysed, metabolized, and removed from the body.…”