Scorpion envenomation in the neotropical savannah: Environmental predictors and years of lost life

Urbanization impact on scorpion stings: An epidemiological study

Accidents caused by venomous animals, especially scorpions, are a major public health problem due to the increase in incidence in recent decades, since scorpion species have become well adapted to urbanized environments. Nonetheless, the impact of urbanization in scorpionism is not clear. The objective of this study is to correlate the variation in the incidence of scorpion accidents with the rate of urbanized area. This was a retrospective, epidemiological study of accidents by scorpions in 376 of the most populous Brazilian cities in 2019 and compared to ten years earlier, using Spearman's correlation coefficient. Data were obtained by accessing DATASUS/TABNET and IBGE Cidades platforms. A weak negative correlation between scorpion stings and urbanization was found in 2009 (rs = -0.145). The correlation between the variation in the incidence of scorpionism and the percentage of urbanized area was not significant. Although the highest incidence of scorpionism occurs in-more urbanized environments, there is a wide distribution of scorpion accidents, especially in tropical and subtropical regions due to climatic conditions, the level of urbanization of Brazilian municipalities was not the major factor in the increase of scorpion accidents.

Divergence in toxin antigenicity and venom enzymes in Tityus melici, a medically important scorpion, despite transcriptomic and phylogenetic affinities with problematic Brazilian species

The Brazilian scorpion Tityus melici, native to Minas Gerais and Bahia, is morphologically related to Tityus serrulatus, the most medically significant species in Brazil. Despite inhabiting scorpion-envenomation endemic regions, T. melici venom remains unexplored. This work evaluates T. melici venom composition and function using transcriptomics, enzymatic activities, and in vivo and in vitro immunological analyses. Next-Generation Sequencing unveiled 86 components putatively involved in venom toxicity: 39 toxins, 28 metalloproteases, seven disulfide isomerases, six hyaluronidases, three phospholipases and three amidating enzymes. T. serrulatus showed the highest number of toxin matches with 80-100 % sequence similarity. T. melici is of medical importance as it has a venom LD50 of 0.85 mg/kg in mice. We demonstrated venom phospholipase A2 activity, and elevated hyaluronidase and metalloprotease activities compared to T. serrulatus, paralleling our transcriptomic findings. Comparison of transcriptional levels for T. serrulatus and T. melici venom metalloenzymes suggests species-specific expression patterns in Tityus. Despite close phylogenetic association with T. serrulatus inferred from COI sequences and toxin similarities, partial neutralization of T. melici venom toxicity was achieved when using the anti-T. serrulatus antivenom, implying antigenic divergence among their toxins. We suggest that the Brazilian therapeutic scorpion antivenom could be improved to effectively neutralize T. melici venom.