|
|
 |
|||||
 |
|
||||
|
October 2005 The CDC has confirmed the first widespread outbreak of Rocky Mountain spotted fever (RMSF) in Arizona. Rickettsia rickettsii, which causes RMSF, is rarely reported in Arizona. However, the CDC investigation documents the presence of this disease in eastern Arizona. The findings indicate that the common brown dog tick may be a vector. J. Stephen Dumler, MD, pathologist, microbiologist and professor at Johns Hopkins University School of Medicine, warns that this is a sign of how humans can inadvertently help spread infectious organisms beyond traditional state boundaries. Dumler highlighted the importance of this outbreak: The first confirmed cases could be traced back to ticks that were carried into the state on feral dogs. The disease has been largely confined to the south, central and southeastern United States, although sporadic cases have been reported in all 48 continental states. He also reported that the number of people with RMSF has peaked for the third known time this century, with more than 1,800 cases reported nationally in 2003 and 2004. However, researchers believe the number of unreported cases is much greater. In the CDC-led study, government researchers took blood and skin tissue samples of 16 patients, whom they suspected had RMSF, from across southeastern Arizona. Laboratory tests, including immunohistochemical staining, confirmed that 11 of these patients had the disease, while the remaining five were probable cases. Of these cases, 81% (13) were among children 12 or younger and 94% were hospitalized. Two of these children died, according to the CDC report.
When the researchers examined the patients’ homes for possible clues to the source of infection, they found dense populations of the ticks. All of the patients with confirmed disease had infected ticks in their yards. Researchers found ticks in the cracks of stucco walls on homes, in crawl spaces under homes and on furniture placed outside for children and pets. All patients owned and had come in contact with dogs with the infected ticks. Four of the patients had a recent history of tick bite. Tests of the dogs’ blood confirmed their infection with R. rickettsii. Feral dogs and brown dog ticks are not a species found naturally in the Arizona region. They were introduced to the state through 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,” said Dumler in a release. Growing awareness among physicians about the disease’s early signs may be the best means of curbing the morbidity of the disease, which can be effectively treated with specific antibiotics if caught early. The first signs of RMSF, Dumler said, are body aches and pains accompanied by headache and a sudden high fever, sometimes as high as 105°F. Symptoms may also include sore throat and nausea. A spotty rash that appears five to 10 days after the first signs of infection often characterizes the infection. The spotty rash, which occurs in at least 85% of patients, does not appear until later in the infection and resembles a pinpoint pattern of pink-to-red spots over the entire body, or parts of it. The rash is also noticeable on the soles of the feet and palms of the hands, where rashes do not usually appear. At this later stage of infection, antibiotic therapy becomes somewhat less effective. Initial treatment for children is doxycycline until the fever subsides, Dumler advised. Before antibiotic therapy, the mortality rate was approximately 30%. Currently, it is about 3% to 5% and occurs mostly in people in whom antibiotic therapy was delayed five to six days after the onset of symptoms. For more information: |
