Comparative analyses of Bothrops fonsecai snake venom: individual variability and sex-based differences

Abstract

Snakebite envenomation is a neglected tropical disease affecting thousands of people globally, especially in tropical and subtropical regions. An estimated 81,000 to 138,000 deaths occur annually, with many survivors experiencing permanent disabilities. In Brazil, around 26,000 cases are reported each year, with the genus Bothrops responsible for 83.8 % of them. Bothrops venoms are rich in metalloproteases, serine proteases, phospholipases A₂, and L-amino acid oxidases, which can cause hemorrhage, tissue necrosis, coagulation disorders, and hypotension. This study focuses on the biochemical and toxicological characterization of Bothrops fonsecai venom, an understudied and near-threatened species endemic to southeastern Brazil, not included in the venom pool for antibotropic serum preparation. Venoms from male and female specimens maintained at the Butantan Institute were compared using standard biochemical, enzymatic, immunological assays, and protein composition. Females tented to exhibited higher enzymatic activity than males in nearly all tests performed. Significant differences were found in EC₅₀ values for indirect hemolysis and in the minimum coagulant dose, also indicating sex-based variation in venom potency. SDS-PAGE and RP-HPLC analyses revealed qualitative and quantitative differences in protein composition between sexes and individually. Immunological assays (ELISA and Western Blotting) demonstrated good immune recognition patterns, with only a few exceptions, which may reflect intraspecific variability in venom antigenicity. Although some biochemical information on Bothrops fonsecai is available, studies remain scarce and fragmented. This work advances current knowledge by providing a broader characterization of the venom and by examining intraspecific patterns—such as sex-related and individual variation—that had not been previously explored in an integrated way. These findings contribute to a more complete understanding of the species, which is especially relevant given its limited representation in venom research and may contribute to improving the effectiveness of antivenom therapies and clinical management of envenomations caused by this species.