Multilocus Sequence Typing Unveils Two Novel Genospecies of Sensu Lato in Ticks Infesting Cricetid Rodents of Northern Chile.

Tick-borne spirochetes of the genus are maintained in enzootic transmission cycles involving wild vertebrates such as rodents. The genus includes the lyme disease group (LDG), transmitted by hard ticks (Ixodidae), and the relapsing fever group (RFG), mostly transmitted by soft ticks (Argasidae). While research on spirochetes has been largely concentrated in the Northern Hemisphere, recent studies have uncovered new genospecies in South American ecosystems. Particularly in Chile, while is the sole species that has been cultured, multiple under characterized strains have been detected in wild rodents and ticks. This study aimed to genetically characterize strains of in ticks parasitizing , an abundant rodent species inhabiting the central north of the country. From 2021 to 2023, rodents were captured at two sites in the Coquimbo Region. Observed ticks were collected, morphologically identified, and submitted to DNA extraction to further detect the presence of spirochetes through nested PCR targeting the gene. Multilocus sequence typing (MLST) of eight housekeeping genes was subsequently performed on positive samples. Pairwise nucleotide comparisons and phylogenetic analyses with the retrieved sequences were conducted using maximum likelihood (ML) and Bayesian inference (BI) methods. A total of 634 were captured, yielding 134 ticks, all identified as spp. Ten ticks genetically identified as or tested positive for spp. Genetic identity and phylogenetic analyses revealed the presence of two novel LDG genospecies in Chile, where was the sole previously known species of the group. Although the vectors and pathogenic roles of these novel genospecies are currently unknown, our study underscores the need for further isolation attempts of the strains to assess their impact on wildlife or human health.