Caracterização fisiopatológica do envenenamento pelas aranhas-marrons Loxosceles amazonica e Loxosceles aff. variegata

Abstract

The brown spider, of the genus Loxosceles, is an arachnid of medical importance in Brazil, as its bite can cause loxoscelism, which can be cutaneous, resulting in skin lesions, or systemic, with severe symptoms. Most cases are cutaneous and less severe, but the underreporting of cases means that the true prevalence of loxoscelism is underestimated. This study characterized the pathophysiological, systemic, and immunological effects of the venom of Loxosceles amazonica (LaV) and Loxosceles aff. variegata (LvV), species whose pathophysiological effects have not been completely described, in vitro and in vivo assays. In vitro assays, LaV demonstrated platelet aggregation capacity, while LvV inhibited washed platelet aggregation. Both venoms caused direct hemolysis of human erythrocytes, with the ABO and Rh systems influencing hemolytic activity. The venom components degraded fibrinogen, suggesting alterations in coagulation. In vivo assays, six female rabbits were used for dermonecrosis assays and biochemical marker evaluation, and mice to determine the DL50 of the venoms and for renal evaluation assays. The DL50 was 1.72 mg/kg for LvV and 1.81 mg/kg for LaV, indicating toxicity similar to that of L. laeta. The rabbits exhibited symptoms of viscero cutaneous loxoscelism, with dermonecrotic lesions, hematological alterations, and serum biochemical changes. Histopathological analyses of envenomed mice confirmed the lesions observed in urinalysis and SDSPAGE, reflecting significant proteinuria and renal damage. It is concluded that LaV and LvV venoms cause a clinical picture similar to that of other Loxosceles species. The study contributes to the understanding of the pathophysiology of envenomation by these species, highlighting the clinical relevance of accidents in the areas where these spiders are found.