This article reports on 5 dogs from the northeastern United States that had Rocky Mountain spotted fever (RMSF) and presented with neurologic disease. Active infection with RMSF was defined by a single high titer or increased titers. The diagnosis was supported by compatible clinical signs and laboratory abnormalities and response to doxycycline. All the dogs had low platelet counts and elevated white blood cell counts. Proteinuria was found in all 3 dogs that had urine results reported. All dogs were hypoalbuminemic, 4 were anemic, and 4 had vestibular system disease. Other neurologic signs included paresis, tremors, and mentation changes. Cerebrospinal fluid was analyzed in 3 of the dogs, and all had elevated protein levels and cell counts. All of the dogs responded fairly rapidly to treatment with doxycycline.

COMMENTARY: Dogs with RMSF have been reported to have neurologic disease similar to the dogs in this study, but the mortality rate is often higher. Of special note in these cases is that 3 of the 5 dogs did not have a reported history of recent tick exposure. Tick-borne diseases need to be included in the differential, even when the owners are not aware of ticks having been on their pets.

Central nervous system dysfunction associated with Rocky Mountain spotted fever infection in five dogs. Mikszewski JS, Vite CH. JAAHA 41:259-266, 2005.