( the infected ticks. Four of the patien...)Infectious disease expert warns of spread of Rocky Mountain spotted fever

Tests of the dogs' blood confirmed their infection with the spotted fever bacterium. Feral dogs and brown dog ticks are not a species found naturally in the Arizona region, but were introduced to the state as domesticated dogs that moved with their owners into the area.

"This study shows that Rocky Mountain spotted fever can show up in unexpected places, and the study should put physicians on alert for the earliest signs and symptoms of the disease," says Dumler. "Our next step is to develop faster and more reliable tests to detect the disease so that physicians can more readily make a diagnosis and begin treatment as early as possible."

Initial treatment for adults, he says, involves immediate, twice daily 100-milligram doses of the oral antibiotic doxycycline (a version of the common tetracycline) until the patient's fever subsides. Patients continue to take the medication for an additional five days to prevent the disease from rebounding. Infected children would receive the same drug, but at a lower dose.

Rocky Mountain spotted fever is a bacterial disease caused by Rickettsia rickettsii, which can be spread by ticks that carry the bacteria and then bite humans, leaving behind the tick's bacteria-filled saliva. Once inside the body, the infection spreads rapidly, causing inflammation of the blood vessels, shock and the build-up of fluid inside the lungs and brain. The precise origins of Rocky Mountain spotted fever are not known, but the disease is only known to occur in North and South America.