Hosts and vectors of scrub typhus in Chile: epidemiological study and molecular analyses of Orientia infection in rodents and rodent-associated mites

Candidatus Orientia chiloensis causes scrub typhus over a wide geographical range in southern Chile. The life cycle, including vectors and reservoirs of this novel rickettsial pathogen, is incompletely understood. We analyzed rodent tissue and rodent-associated mite samples collected during a field study in six localities on Chiloé Island, where human scrub typhus cases have occurred. Using molecular methods, we detected Orientia DNA in 24.8% of rodents, belonging to five of seven captured species. Orientia-infection rates showed geographical variations, but were not influenced by rodent species, sex, age, and mite infestation. Phylogenetic analysis showed that Orientia sequences from trombiculid mites (Proschoengastia eloisae) were identical to those from scrub typhus patients from the same region. The results suggest that these rodent-associated mites serve as vectors and play an important role in the ecology of scrub typhus in southern Chile. Further studies are required to determine whether Orientia-infected rodents can also serve as reservoir of Orientia in Chile.