Mapping Potential Risks for the Transmission of Spotted Fever Rickettsiosis after Environmental Changes in an Atlantic Forest Region in Brazil.

Brazilian Spotted Fever (BSF), caused by Rickettsia rickettsii, is a fatal tick-borne disease endemic to southeastern Brazil. This study evaluates the eco-epidemiology of BSF in Santa Cruz do Escalvado, Minas Gerais, a region impacted by significant environmental changes following the 2015 Fundão dam collapse. We conducted serological and molecular surveys of mammals (n = 97) and ticks (n = 1,123) to assess pathogen circulation. Serological analysis revealed a 27.5% prevalence of anti-R. rickettsii antibodies in dogs, a marked increase compared to historical data (2% in 2009) from the same region. Conversely, wildlife sentinels (opossums, capybaras) showed minimal seroreactivity. Molecular screening of ticks identified Rickettsia bellii and a Rickettsia tamurae/Rickettsia monacensis-like genotype in Amblyomma dubitatum and Amblyomma sculptum, respectively; however, R. rickettsii DNA was not detected in any vector. These findings suggest a dichotomy in transmission cycles: a peri-urban cycle with high canine exposure driven by A. sculptum, and a riparian cycle involving A. dubitatum harboring non-R. rickettsii agents. The discrepancy between high canine seropositivity and the absence of R. rickettsii in vectors suggests that cross-reactivity with emerging SFG rickettsiae may be confounding surveillance signals, highlighting the need for specific molecular diagnostics in risk assessment.