A tick-borne
disease similar to Lyme disease has been popping up in southern states
and other areas of the country since the 1990s and scientists still are
trying to figure out if this is a new disease or simply a Lyme variant.
The Centers
for Disease Control and Prevention in Atlanta is funding studies to determine
the cause of the ailment, which has been dubbed Master's disease, but so
far the culprit has remained unidentified.
Sam Telford,
a researcher at Harvard University who focuses on Master's disease and
will present an overview of it next month at the Ninth International Conference
on Lyme disease and other tickborne diseases in New York City, told United
Press International, "For the first time (at the conference), Master's
disease is being considered as an entity separate from Lyme disease."
"There's a
lot of interest in it" and the conference should help extend the knowledge
about the disease, Telford said.
Although the
symptoms of Master's disease are quite similar to Lyme disease and include
the "bulls-eye" rash that is Lyme's hallmark, as well as fever, fatigue
and achiness, it appears to be caused by a different tick and a different
bacterium.
Ned Hayes,
a medical epidemiologist with the Lyme disease program at the CDC, told
UPI since the early 1990s more than 100 people have been diagnosed with
the mysterious condition. CDC prefers the name Southern tick-associated
rash illness, or STARI, but some scientists consider this designation inaccurate.
Master's disease
was first identified in Missouri in 1991 when 45 patients developed the
bulls-eye rash.
However, subsequent
investigation of these patients failed to identify Borrelia burgdorferi,
the Lyme bacteria.
In addition,
the infected people did not produce the expected antibodies -- proteins
produced by the body in response to an infection -- specific for Lyme,
which indicated their rashes were caused by some different germ.
Several more
clusters of people developed this rash throughout the 1990s without revealing
Lyme disease as the culprit. There were 23 additional cases in Missouri,
14 cases in North Carolina and 23 in Georgia. Sporadic cases also have
been reported "among military personnel doing field maneuvers in southern
states," Hayes said.
Scientists
eventually discovered in most of these cases people had reported being
bitten by a type of tick called a lone star tick -- Amblyomma americanum
-- so named because of a yellow star-shaped patch on its back. This tick,
which does not usually transmit the Lyme disease bacteria, is quite different
from the deer tick, which transmits Lyme bacteria to humans.
Lone star ticks
occur in the southeastern states from Texas to Florida and up to Virginia,
whereas the deer tick's range primarily is in the northeastern states,
which is where most Lyme disease cases occur.
"We still don't
know what causes (Master's disease)," Hayes said, but many scientists now
think it is caused by an as-yet-unidentified bacterium similar to the Lyme
disease germ.
Although no
one has seen this new organism yet, researchers have detected its DNA in
lone star ticks and in at least one person's rash. "So we think its coming
from a new species of (bacteria)," Hayes said.
The bacterium
has been named Borrelia lonestari and it may be similar to a bacterium
that caused fever in cattle at the turn of the 20th century, Telford said.
The CDC currently
is funding a study to identify the cause of the illness definitively. The
effort involves taking tissue samples from the rash site and looking for
the DNA of this new bacterium. The next step is to show conclusively people
with the rash are infected with Borellia lonestari, Hayes said. But it
could be that the bacterium is not the cause of the problem, he noted.
Telford agreed,
saying, "The evidence isn't there yet" to put the blame on B. lonestari.
He noted Ed Masters -- a family doctor in private practice in Missouri
for whom the disease was named -- has had hundreds of tissue samples from
patients with the illness tested for the DNA of B. lonestari and no one
yet has detected any indication of the organism in any of the samples.
Telford thinks
there "may be multiple causes of Master's disease," including a reaction
to the tick bite itself, a new species of bacteria or some other unrecognized
agent. "Whatever it is, it's unique to the lone star tick," he said.
Masters told
UPI the illness could have multiple causes and it might be too early to
call it a new disease. "We're still on the front end of a very steep learning
curve," he said, noting the rash and the symptoms of the disease are identical
to Lyme and no one has proven which bacteria is the true cause. So it very
well could be a variant of Lyme carried by lone star ticks instead of deer
ticks.
The good news
is although symptoms of Master's disease can be similar to Lyme disease,
they seem less severe and they disappear on their own. Lyme disease's symptoms,
on the other hand, can linger for years, if not indefinitely, and can cause
neurological problems and even affect the heart.
"Most of the
time the rash is the most prominent symptom," Hayes said. About half the
people who develop Master's disease report fatigue, 43 percent have headache,
about 36 percent have aching muscles and 29 percent have fever.
"Most physicians,
if they see the (Master's disease) rash, will treat it with doxycycline
because they think its Lyme disease," Hayes said. Doxycycline is an antibiotic
that can knock out Lyme disease if treatment is begun early enough.
Doxycycline
also seems to knock out the symptoms of Master's disease, Hayes said. "But
whether the symptoms would've went away anyway is anybody's guess," he
said, noting in patients who did not receive treatment, the rash, headache
and muscle aches went away eventually.
Doctors are
not required to report cases of this disease to state health departments
or the CDC, so it is unclear how many cases there have been across the
country. "There's no indication that this is spreading," Hayes said.
Telford and
Masters disagreed, saying they believe the disease often is confused with
Lyme and therefore it is probably more prevalent than expected. Telford
said the incidence of Master's disease "must be huge because these ticks
are just a nightmare.
They're so abundant
and very aggressive. They're places where you could get 2,000 ticks crawling
up your leg."
Masters noted
"the lone star tick is expanding its territory" and this could increase
the number of cases of people who develop Master's disease. The disease
may be expanding outside of the southern states to some northern states
such as Iowa because people have come down with Lyme disease symptoms there
even though they probably were not exposed to deer ticks, he said.
To prevent
infection with Master's disease, people should observe the same precautions
to avoid Lyme disease, Hayes said. These include using insect repellent,
wearing light-colored clothing so the ticks can be spotted easily and removing
them from the body as soon as possible.
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Copyright 2002 by United
Press International.
All rights reserved.
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