A Study of Canine Rocky Mountain Spotted Fever Prevalence Seen in a South Carolina Veterinary Lameness and Performance Referral Center

Rocky Mountain spotted fever (RMSF), caused by Rickettsia rickettsii, is a potentially severe tick-borne disease affecting both dogs and humans. While commercial in-clinic diagnostic tests have improved the detection of several common canine tick-borne diseases, RMSF is not routinely included in many point-of-care screening panels. In addition, infected dogs may present with subtle or nonspecific clinical signs, making diagnosis challenging. This retrospective observational study evaluated the occurrence of PCR-confirmed Rickettsia rickettsii infection in dogs presented to a veterinary lameness and performance referral center. From March 2022 through February 2024, a convenience sample of 51 dogs underwent RMSF testing as part of their diagnostic evaluation. Blood samples were analyzed using a commercial vector-borne disease PCR panel. Overall, 13 of 51 dogs (25.5%) were PCR-positive for Rickettsia rickettsii. Thirty-six dogs originated from North Carolina and South Carolina, of which 13 (36.1%) were PCR-positive. These findings suggest that RMSF should be considered among the differential diagnoses in dogs presenting with unexplained lameness, reduced athletic performance, or other nonspecific clinical concerns in regions where tick-borne diseases are common. The identification of PCR-confirmed Rickettsia rickettsii infection in this referral population highlights the potential value of expanded vector-borne disease testing.