New tick-borne illness has researchers scratching heads
Pastor Dale Morgan
New tick-borne illness has researchers scratching heads*
St. Louis Post-Dispatch
Wednesday, August 23, 2006
ST. LOUIS COUNTY - It’s a miserably muggy morning, and Brian Allan is
tucking the pant legs of his white cotton jumpsuit into his socks.
A mysterious new tick-borne disease has sickened people and puzzled
doctors, and Allan, a Washington University graduate student, is out to
track down its source.
Trudging through woods at the Tyson Research Center, he pauses every 20
feet to inspect a white cotton cloth about the size of an American flag
that he’s dragging. He also inspects himself.
On this particular July morning, the search so far is not very tickful
for Allan, who can usually find a tick within one minute.
He has traveled throughout the Midwest to collect ticks. He’s been all
over Missouri, southern Indiana and to Land Between the Lakes in
Kentucky and Tennessee. This month, he’ll have a tick collecting spree
in southern Missouri.
Allan is part of a Washington University effort to find which animals
are passing on tick-borne diseases, including the new elusive one.
Last year, Missouri had 213 reports of tick-borne diseases, including
Lyme disease, erhlichiosis and Rocky Mountain spotted fever. The actual
number of cases is most likely higher because these diseases can be
difficult to diagnose.
Missouri long has been considered a hot spot for tick-borne diseases.
"Rural Missouri is a hazardous place to be in the summer," said Gregory
Storch, an infectious disease expert at Washington University. The most
tick bites occur in April through September, he said.
The new pathogen, which causes rashes and flu-like symptoms, has Storch
and his fellow researchers on a mission.
"It’s out there in nature, but no one knows where," said Robert Thach,
one of the study’s collaborators. "Why are people in St. Louis coming
down with this disease? Where are they getting it? Where are the ticks
getting it?"
The disease is considered an emerging infection, and too little is known
about its causes to be classified by the Centers for Disease Control and
Prevention as a nationally reportable disease.
But the disease does have a name: Southern tick-associated rash illness.
Donald Kennedy, professor of internal medicine at St. Louis University
School of Medicine, treated two patients with the illness in May. He
said that for now, the illness is considered a clinical syndrome because
the pathogen that causes it has not been identified.
"Some of these techniques in identification lag the presentation of the
clinical illness," Kennedy said.
The same was true for other infectious diseases, including AIDS, polio
and smallpox, he said.
Part of the new disease’s mystery is that its victims show symptoms
similar to those of people with Lyme disease. Both cause a bull’s-eye
rash, and victims complain of headaches, muscle aches and fatigue. But
tests for the organism causing Lyme disease come back negative for
patients with the new illness.
Although some researchers suspect that the organism causing the new tick
disease is related to the bacterium that causes Lyme disease, they’re
also convinced that this new disease is not Lyme.
What is known is the type of tick that transmits the illness: the
lonestar tick. Named for the white spot on the adult female’s back, the
lonestar tick is the most frequently encountered tick in Missouri. This
spider relative’s habitat stretches from Florida to Texas to Maine.
Most ticks seek their blood meals by clinging to tall grasses with their
six rear legs and waving their front two as they wait for a host - such
as a human, deer, chipmunk or bird - to brush by it. Not so for the
lonestar tick.
"A lonestar will actually run toward a host and try getting on that
way," said Karen Yates, an ecologist at the Missouri Department of
Conservation. "It’s a supertick."
When Allan scores ticks on his cloth, he plucks them off with tweezers
and places them in small vials containing ethanol. The ethanol preserves
the ticks so that Lisa Goessing, a Washington University researcher, can
isolate a tick’s last blood meal, which might have been eight months before.
The blood meal contains DNA that identifies the animal that the tick fed
on, as well as any pathogens the animal was carrying. This information
will show the researchers which animals are more likely to pass on disease.