Rocky Mountain spotted fever is a systemic disease of dogs in all of the Americas that can also affect humans. Rocky Mountain spotted fever is caused by the bacteria Rickettsia rickettsii, which is transmitted by ticks. The disease may occur in dogs without prior known exposure to ticks. Some infected animals have no clinical signs. The most common clinical signs include the following: fever, lethargy, decreased appetite and possible severe weight loss, vomiting, diarrhea, coughing, inflammation and hemorrhages within the eyes, joint and muscle pain. Neurological signs that can arise are seizures, pain along the neck and back, uncoordinated movement, head-tilt, falling and more.
Routine laboratory tests are commonly recommended to investigate the clinical signs. A complete blood count may show low numbers of red blood cells and white blood cells. A biochemistry panel may reveal low protein levels and elevated cholesterol, liver and kidney values. Urinalysis may show abnormally high protein in the urine. Blood tests for Rocky Mountain spotted fever are commonly done and these need to be repeated in two weeks. There are new PCR tests that help determine whether the bacterial DNA may be present.
The antibiotic doxycycline is the most commonly recommended treatment for Rocky Mountain spotted fever. Other treatments include anti-inflammatories for the severe inflammation that occurs in the joints and to inhibit the effects of the bacteria on the blood cells.
Resolution or substantial improvement of the signs often occurs within the first 48-72 hours after starting treatment, especially when therapy is begun early in the course of the illness. Periodic examination and repeated laboratory testing are often used to monitor response to treatment. Animals that have Rocky Mountain spotted fever are commonly exposed to other diseases transmitted by ticks, so installation of a strict comprehensive control program is very important.
Prognosis is generally good for animals that are mildly affected. Rocky Mountain spotted fever is potentially zoonotic, meaning that it is transmissible from animals to humans. If an animal is suspected of having Rocky Mountain spotted fever, people in the vicinity should take precautions to prevent tick bites.
Dr. Karsten Fostvedt is a veterinarian at St. Francis Pet Clinic in Ketchum.