Reactive Mechanical Control and Sting Incidence: An 18-Year Distributed Lag Analysis of Urban Scorpionism

Urban scorpionism associated with Tityus serrulatus Lutz & Mello remains an increasing concern in Neotropical cities. Reactive mechanical control is widely implemented as a primary control strategy; however, its long-term association with changes in envenomation incidence is still poorly quantified. This study evaluated whether variation in capture intensity was associated with subsequent reductions in scorpion sting incidence. A distributed lag non-linear model (DLNM) was applied to an 18-year time series (2007-2024; 216 months) of scorpion stings and capture effort. Capture intensity (scorpions per field-day) was considered the main exposure, with lagged effects evaluated over a 12-month period. Models were adjusted for temperature and rainfall using natural cubic splines. A quasi-Poisson framework was used to account for overdispersion, and model robustness was assessed through sensitivity analyses and residual diagnostics. High-intensity reactive mechanical control (90th percentile) was not associated with reduced sting incidence at lag 0 (RR: 0.973; 95% CI: 0.892-1.062), and estimates remained close to the null across the full lag structure (0-12 months). Temperature was also not independently associated with sting incidence after adjustment, and no delayed effects were observed. Cumulative associations were similarly non-significant, and sensitivity analyses indicated stable model estimates across specifications. Overall, the results suggest that increased reactive mechanical control intensity was not associated with measurable reductions in scorpion sting incidence within the studied urban system. Within the studied urban system, these findings are consistent with ecological expectations for highly resilient, parthenogenetic species, in which localised removal may not translate into detectable changes in population-human interaction dynamics.