Prevalence of Antibodies to Spotted Fever Group Rickettsiae in Dogs from Southeastern Australia

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  • Division of Infectious Diseases, Duke University Medical Center, Fairfield Infectious Diseases Hospital, School of Veterinary Science, The University of Queensland, Durham, North Carolina, Australia

Recent epidemiologic data suggests that Rickettsia australis, the cause of Queensland tick typhus, is present in southeastern Australia. In order to further confirm this observation, a canine serosurvey was undertaken to determine if naturally occurring antibodies were present in pet and farm dogs from this newly-recognized endemic area. Thirty-five of 312 surveyed dogs (11.2%) had indirect immunofluorescent antibody titers of 1:64 or greater against R. australis antigen. Positive control sera were obtained from two dogs experimentally inoculated with R. australis. One of these dogs was serially sampled and a rickettsemia could not be documented. None of 26 control sera obtained from dogs from South Australia, New Zealand, western Victoria, or North Carolina had antibody titers ≥ 1:64. These results suggest that spotted fever group rickettsiae are present in Southeastern Australia.