Rocky Mountain Spotted Fever (RMSF)

Rocky Mountain spotted fever (RMSF) is an infectious, tick-borne disease caused by the organism Rickettsia rickettsii. Ticks infected with Rickettsia rickettsii transmit the disease when they feed on a host (dog, human, other large mammal). A tick must be attached to the host for 5 to 20 hours before it can transmit the disease.

Rocky Mountain spotted fever occurs most often in the spring and summer when ticks are most active. Dogs at increased risk include those younger than four years of age and large breed dogs primarily because these dogs are more likely to be outdoors. Purebred dogs are more likely to develop the symptoms of RMSF after infection than are non-purebred dogs and German shepherd dogs may be at higher risk than other breeds.

With an active RMSF infection, any organ in the body may be affected.

What To Watch For

Fever, usually over 104 degrees Fahrenheit

Depression

Decreased appetite

Lymphadenopathy, or generalized enlargement of lymph nodes

Petecchiae, or pinpoint hemorrhages under the skin

Uveitis, which is inflammation of the interior of the eye

Swollen or painful joints

Diagnosis

Veterinary care should include diagnostic tests to determine the underlying cause and help guide subsequent treatment recommendations. These tests may include:

Complete blood count

Biochemistry profile

Urinalysis

Coagulation tests

Indirect fluorescent antibody (IFA) testing

Coomb's test

Antinuclear antibody test (ANA)

Treatment

Depending on the severity of infection and clinical symptoms, affected pets may require hospitalization for several days.

Tetracycline antibiotics (oxytetracycline, doxycycline) or chloramphenicol are the antibiotics of choice to treat rickettsial diseases.

Intravenous fluids are administered to pets that are actively vomiting, dehydrated from vomiting or have evidence of kidney insufficiency due to RMSF.

Colloids are administered to prevent edema in pets with low blood protein levels.

Administration of plasma may be necessary in pets with bleeding abnormalities or with exceptionally low blood protein levels.

Nutritional support may be necessary in pets that have not eaten for several days or have protracted vomiting.

Home Care and Prevention

Administer antibiotics as directed by your veterinarian. Antibiotic therapy is usually continued for a 2 to 3 week period. It is important to finish all medications as directed because infection may reoccur if therapy is discontinued too soon.

If you are having difficulty administering the medication, or the antibiotic causes nausea or vomiting in your pet, contact your veterinarian as soon as possible.

There is no vaccine available for protection against RMSF. Pets that have been infected are immune to re-infection for 9 to 12 months. You should inspect your pet for ticks regularly when the pet comes in from outdoors, particularly in the spring and summer when ticks are most active. Remove ticks from pets as soon as they are detected. Ticks infected with Rickettsia rickettsii must be attached for 5 to 20 hours before they can transmit the organism to your pet. If the tick is removed before this time, transmission cannot occur.

Take care to prevent your own exposure when removing ticks from your pet. Wear gloves or use tweezers to prevent fluid from crushed ticks from contacting abraded areas on your skin. If your yard is heavily infested with ticks, consider an environmental spray to control tick numbers.

Use oral or topically applied tick preventative medication to deter and kill ticks before they can harm your pet.