Experimental Infection of Amblyomma aureolatum Ticks with Rickettsia rickettsii

We experimentally infected Amblyomma aureolatumticks with the bacterium Rickettsia rickettsii, the etiologicagent of Rocky Mountain spotted fever (RMSF). These ticksare a vector for RMSF in Brazil. R. rickettsii was effi cientlyconserved by both transstadial maintenance and vertical(transovarial) transmission to 100% of the ticks through4 laboratory generations. However, lower reproductive performance and survival of infected females was attributedto R. rickettsii infection. Therefore, because of the highsusceptibility of A. aureolatum ticks to R. rickettsii infection,the deleterious effect that the bacterium causes in theseticks may contribute to the low infection rates (<1%) usuallyreported among fi eld populations of A. aureolatum ticksin RMSF-endemic areas of Brazil. Because the numberof infected ticks would gradually decrease after eachgeneration, it seems unlikely that A. aureolatum ticks couldsustain R. rickettsii infection over multiple successivegenerations solely by vertical transmission...