Rickettsial Infection in Animals and Brazilian Spotted Fever Endemicity

TLDR: Surveys of horse serum are a useful method of surveillance for Brazilian spotted fever in areas where humans are exposed to Amblyomma cajennense ticks.

Abstract: We compared the rickettsial infection status of Amblyomma cajennense ticks, humans, dogs, and horses in both Brazilian spotted fever (BSF)–endemic and –nonendemic areas in the state of Sao Paulo, Brazil Most of the horses and few dogs from BSF-endemic areas had serologic titers against Rickettsia rickettsii antigens In contrast, no dogs or horses from BSF-nonendemic areas had serologic titers against R rickettsii antigens, although they were continually exposed to A cajennense ticks All human serum samples and ticks from both areas were negative by serologic assay and polymerase chain reaction, respectively Our results indicate that surveys of horse serum are a useful method of BSF surveillance in areas where humans are exposed to A cajennense ticks In addition, we successfully performed experimental infection of A cajennense ticks with R parkeri