In a rural area of Colombia endemic for Rocky Mountain spotted fever, we performed indirect immunofluorescent antibody assays for Rickettsia spp. and Ehrlichia spp. using sera from randomly sampled dogs and horses to test the use of domestic animals as possible sentinels. Antibodies against Ehrlichia spp. were detected in 8 dogs (31.8%). Antibody titers against Rickettsia rickettsii antigen were positive in 4 dogs (18.2%) and 26 horses (16.3%). These values, albeit not directly comparable, are lower than those previously reported for humans in this region. A systemic approach to understanding dynamics of transmission is needed before implementing the use of domestic animals for disease surveillance activities.