Seroepidemiological survey to investigate Rickettsia rickettsii and Rickettsia parkeri in municipalities of the southeast Brazil.

Spotted fever is a tick-borne rickettsiosis caused by several Rickettsia species-including R. rickettsii, R. parkeri, and others-with varying degrees of pathogenicity. Its nonspecific symptoms often lead to misdiagnosis such as dengue. This study investigated anti-R. rickettsii and R. parkeri antibodies in 152 patients with acute febrile illness who tested negative for dengue. Serological analysis using immunofluorescence assay found 29 reactive samples (19%) at a 1:64 dilution. Among them, 20.6% were male and 58.6% female, with an average age of 42.6 years. The average sample collection time totaled 14.6 days. Reactive samples included 13.1% for R. rickettsii and 5.9% for R. parkeri. These results suggest possible rickettsial infections in patients initially suspected of dengue.