Rocky Mountain Spotted Fever

Rocky Mountain Spotted Fever (RMSF) is primarily a disease of dogs and people that is caused by infection with Rickettsia rickettsii bacteria that are transmitted through the bites of ticks. RMSF is commonly diagnosed in dogs that live in or travel to areas where ticks are prevalent. The bite of one infected tick, which can be easy to miss, is sufficient to cause the disease, so lack of a known exposure to ticks does not rule out a diagnosis of Rocky Mountain Spotted Fever.




Symptoms of RMSF can include fever, lethargy, enlarged lymph nodes, abnormal swellings, limping, coughing, difficulty breathing, vomiting, diarrhea, and bruising and bleeding. In order to diagnose Rocky Mountain Spotted Fever, differentiate it from other diseases that cause similar symptoms (e.g., ehrlichiosis, Lyme disease, lymphosarcoma, and immune disorders), and to plan appropriate treatment, veterinarians will often order blood cell counts, chemistry panels, and tests that can determine whether or not an animal has been exposed to Rickettsia bacteria.




Certain types of antibiotics are very effective against Rickettsia bacteria, and once treatment begins, an affected animal's condition will usually improve rapidly. In more severe cases, hospitalization for supportive care may be necessary until a dog's condition stabilizes. Many cases of Rocky Mountain Spotted Fever can be prevented through the use of effective tick control products. Dogs that have contracted the disease once are immune against subsequent infections. People can develop Rocky Mountain Spotted Fever but not through casual contact with a sick dog.


Written by: Jennifer Coates, DVM
Last reviewed: October 2, 2008