A comprehensive overview of fish envenomation and venom toxicity in Brazil

Background: Brazilian waters are home to various venomous fish species, each with its unique venom composition. Although common, envenomation cases are largely underreported, leading to a lack of public health policies for prevention and treatment. Some of the most clinically relevant fish in Brazil include the stingray Potamotrygon orbignyi, the toadfish Thalassophryne nattereri, the scorpionfish Scorpaena plumieri, and the catfish Pseudoplatystoma fasciatum and Cathorops spixii. Methods: We comprehensively searched reports about accidents involving venomous fish in Brazil and compared the toxic activities of some medically relevant species. Results: From the biochemical and toxicological evaluation, we found that venoms show a hierarchy in the ability to induce local toxic effects in mice, probably related to the venom compound diversity with species-specific toxins. T. nattereri venom presents greater toxicity, causing more severe local responses than that of P. orbignyi, C. spixii, and P. fasciatum, which cause moderate reactions. The S. plumieri venom induced only a moderate level of edema and could not cause nociception or necrosis. These results highlight that envenomation by P. orbigny, C. spixii, and S. plumieri is marked by proteins with intense hemolytic/proteolytic and phospholipase activity. On the other hand, T. nattereri and P. fasciatum offered a broader panel of new toxin families. Conclusion: Knowledge of fish venom biochemical and toxicological activities is crucial to antivenom therapy development and helps endorse the study of venomous fish and their impact on the public health system.