The mosaic of Rickettisae from the Caatinga Biome, Brazil: New records and first interactions

Rickettsiosis are infections that have worldwide distribution, also occurring in all regions of Brazilian territory and being distributed across its various biomes. The most relevant rickettsiosis in Brazil is Spotted Fever (SF), a potentially lethal zoonosis. Although cases of SF have been confirmed in southeastern Brazil, the epidemiological situation in the Northeast remains poorly understood. The aim of this study was to analyze the circulation and identification of Rickettsia species in the state of Ceará, a northeastern state with confirmed SF cases since 2010. In parallel, we identified potential vectors, as to contribute to the development of an eco-epidemiological profile of Rickettsiae in the state. Genomic DNA samples, extracted from ticks collected in areas with suspected cases, were analyzed via PCR to detect Rickettsia spp., with positive samples undergoing further characterization and genomic sequencing for ompB (SFG-IF/SFG-TG IR) and htrA (17Kd1/17Kd2) genes via Nested PCR. Our results detected, for the first time, the presence of Rickettsia amblyommatis and R. asembonensis in the region. These findings demonstrated the geographical expansion of Rickettsiae in northeastern Brazil. Additionally, we identified the first interaction between Rickettsia parkeri and Amblyomma parvum , signaling a potential change in our understanding of interactions between these species. Altogether, our study reveals a new panorama regarding Rickettsiae in northeastern Brazil.