Molecular detection of Rickettsia spp. in ticks (Ixodida: Argasidae and Ixodidae) and mites (Trombiculoidae) from a brazilian taxonomic collection

Rickettsia species are arthropod-hosted endosymbionts with a wide range of ecologies, including induction of parthenogenesis, male-killing, and even plant pathogens with potential horizontal transmission through a plant host, although they attract greater attention for including many vertebrate pathogens. The genus is classified into phylogenetic and serological groups, heterogeneous concerning their ecologies. This study aims at screen ticks and mites deposited in Acarological Collection at Center of Taxonomical Collections at Universidade Federal de Minas Gerais, Brazil, for rickettsial occurrences, making available genetic data on hosts and bacteria. Endogenous mitochondrial markers for ticks and mitochondrial and nuclear genes for chiggers were sequenced for sample quality control and species identification. A total of 38 soft ticks belonging to the genus Ornithodoros (at least six putative species), 18 hard ticks belonging to the genus Amblyomma (7 spp), and 52 chiggers belonging to genus Whartonia (2 spp) led to sequences. Polymerase Chain reactions for a Citrate Synthase gene fragment led to 21 sequences grouped in the phylogroups Bellii, Spotted Fever, and Transitional, with one sequence of Rickettsia obtained from Amblyomma dubitatum (identified as R. bellii), eight sequences from Ornithodoros (classified in five or six strains associated to the phylogroups Belli, Spotted Fever and Transitional) and twelve associate to Whartonia pachywhartoni (three likely in the Spotted Fever and nine in the Transitional phylogroup). Considering the diversity of rickettsial occurrences in Ornithodoros , with four of the nine strains detected only in O. fonsecai, a species known to bite humans, the medical relevance of Rickettsia associated with caves and bats needs to be further investigated.