An infectious disease expert at Johns Hopkins who has
spent nearly three decades studying the life-threatening,
tick-borne infection known as Rocky Mountain spotted fever,
warns that the first widespread outbreak of the bacterial
disease in Arizona is a growing and dangerous sign of how
humans can inadvertently help spread infectious organisms
beyond traditional state boundaries.
In an article published in the New England Journal
of Medicine, pathologist and microbiologist J. Stephen
Dumler, a professor in the School of Medicine, highlights
the importance of the recent outbreak in Arizona as the
first confirmed cases that could be traced back to ticks
carried into the state on feral dogs, an animal group whose
population has markedly increased. And, as the number of
dogs has increased, so have the number of ticks. A detailed
study of this latest outbreak by the Centers for Disease
Control and Prevention is featured in the same edition of
the NEJM online Aug. 11.
According to Dumler, the disease, most often marked by
a telltale spotty rash that appears five to 10 days after
the first signs of infection, has been largely confined to
the South Central and Southeastern United States, although
sporadic cases have been reported in all 48 continental
states, mostly North Carolina. (Maryland is among the top
10 states for the disease, with at least 79 cases reported
in 2004, up from 19 in 2000.)
The scientist also reports that the number of people
infected with Rocky Mountain spotted fever, which is fatal
in up to 10 percent of those who contract it, has peaked
for the third known time this century, with more than 1,800
cases reported nationally in 2003 and 2004. However,
scientists believe the number of unreported cases is much
Dumler's opinion is that growing awareness among
physicians about the disease's early signs and symptoms may
be the best means of curbing the potentially deadly impact
of the disease, which can be effectively treated with
specific antibiotics if caught early.
"Rocky Mountain spotted fever is a dangerous and
potentially fatal disease, unlike its more widespread
cousin, Lyme disease, which is almost never fatal," he
said. In the latest study, researchers at the CDC report on
16 cases in which two children contracted the fever and
died. "Because its first symptoms are very hard to
distinguish from many other illnesses, it is often hard to
diagnose unless you are looking out for it," he said.
The first signs of Rocky Mountain spotted fever, the
scientist said, are bodywide aches and pains accompanied by
headache and a sudden high fever, sometimes as high as 105
degrees. Symptoms may also include sore throat and nausea.
The spotty rash, which occurs in at least 85 percent 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 thereof. 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
In the CDC-led study, government researchers took
blood and skin tissue samples from 16 patients across
southeastern Arizona suspected of having the infection.
Laboratory tests, including immunohistochemical staining,
confirmed that 11 had the disease, while the remaining five
were still probable cases.
When the researchers examined the patients' home
environments for possible clues to the source of infection,
they found fever-infected ticks in all patients' yards.
Ticks were found in the cracks of stucco walls on patients'
homes, in crawl spaces under these 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 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," Dumler said. "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 said, 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 buildup 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.