Exploring the diversity of Rickettsia in carnivores of the Brazilian cerrado: An analysis of the relationship with ticks

The proximity of wildlife reserve areas to anthropized regions facilitates the spread and exchange of infectious agents, including pathogens with zoonotic potential, thereby increasing health-related risks for species already threatened with extinction. This study investigated the presence of Rickettsia in wild carnivores of the Brazilian Cerrado. Blood and ectoparasite samples were collected from specimens of the families Canidae (Cerdocyon thous, Chrysocyon brachyurus, Lycalopex vetulus, Speothos venaticus), Mephitidae (Conepatus semistriatus), Procyonidae (Nasua nasua), and Felidae (Leopardus pardalis, Panthera onca, Puma concolor). These samples were screened for Rickettsia using serological analysis (IFA) and molecular techniques (PCR). A total of 68 blood samples were obtained from carnivore specimens, along with 210 ticks collected from 18 individuals. DNA extracted from whole blood samples and from 189 ticks were subjected to PCR targeting the rickettsial genes gltA and ompA. Tick species were identified as Amblyomma tigrinum, Amblyomma sculptum, Amblyomma parvum, Amblyomma ovale, Amblyomma auricularium, and Rhipicephalus linnaei. None of the whole-blood DNA samples amplified the gltA gene, but 31 out of 189 tick DNA samples amplified fragments of the gltA and ompA genes, which were identified by DNA sequencing to correspond to four different rickettsial agents: 'Candidatus Rickettsia andeanae', Rickettsia amblyommatis, and the human pathogens Rickettsia parkeri sensu stricto (s.s.) and Rickettsia parkeri strain Atlantic rainforest. Serological analysis by IFA was performed on 50 serum samples. Among those collected in situ, 69% (20/29) of C. brachyurus and 77% (7/9) of C. thous showed seroreactivity to Rickettsia spp. In addition, a probable antigen involved in a homologous reaction (PAIHR) was identified as R. parkeri in 20% (6/29) of C. brachyurus samples and 44% (4/9) of C. thous samples. This is the first report providing both serological and molecular evidence of Rickettsia infection in different wild carnivore species and their ticks in the Cerrado biome. The detection of R. parkeri in wild canids highlights the importance of monitoring infectious agents to inform conservation strategies and zoonosis prevention efforts.