Rickettsial infection in capybaras (Hydrochoerus hydrochaeris) from Sao Paulo, Brazil:: serological evidence for infection by Rickettsia bellii and Rickettsia parkeri

Introduction. In Brazil, capybaras (Hydrochoerus hydrochaeris) are important hosts for Amblyomma ticks, which in turn can transmit rickettsiae to humans and animals. Therefore, capybaras are potential sentinels for rickettsial infection. Objective. The present study evaluated rickettsial infection in capybaras in different areas of the state of Sao Paulo, where rickettsiosis has never been reported. Materials and methods. Blood sera from 73 capybaras from six localities in Sao Paulo were tested by indirect immunofluorescence assay using Rickettsia rickettsii, Rickettsia parked, and Rickettsia bellii antigens. Capybara spleens were tested by PCR, targeting a fragment of the rickettsial gltA gene. Ticks were collected from each capybara sample and taxonomically identified to species. Results. A total of 94 positively reacting capybara. samples, 19 (26.0%), 25 (34.2%), and 50 (68.5%) capybara. sera reacted to R. rickettsii, R. parkeri, and R. bellii, respectively. Twenty-five capybara sera showed titers to R. bellii at least four-fold higher than to any of the other two antigens. These sera were considered homologous to R. bellii. Using the same criteria, 3 capybara sera were considered homologous to R. parkeri. No sera were be considered homologous to R. rickettsii. No rickettsial DNA was detected in capybara spleen samples. Ticks collected on capybaras were Amblyomma dubitatum and Amblyomma cajennense. Conclusions. The first evidence is reported of R. bellii natural infection in vertebrate hosts, and the first evidence of R. parkeri infection in capybaras. While R. parkeri is known to infect and cause disease in humans, no similar evidence for human infection has been indicated by R. bellii.