Spotted fever group rickettsial infection in dogs from eastern Arizona: how long has it been there?

A serosurvey of free-roaming dogs for antibodies to spotted fever group rickettsiae was conducted using archival samples that had been collected in the White Mountain region of eastern Arizona during a plague study in 1996. Immunoglobulin G antibodies to Rickettsia rickettsii (5.1%) and to R. rhipicephali (3.6%) were demonstrated, and no cross-reactive samples were identified. This study indicates that R. rickettsii was likely present in the dog populations in this area prior to the recognition of human cases of Rocky Mountain spotted fever (RMSF). The role of dogs as short-term reservoirs and primary hosts for the vector tick, Rhipicephalus sanguineus, should receive closer attention.