Detective Work Uncovers New Tick-Borne Disease in North Carolina and the Southeast
DURHAM, N.C. -- Kathryn Kirkland spent two years in the
woods of North Carolina on the trail of an elusive,
blood-sucking pest, dubbed Lone Star, that left rashes on the
skin of its victims and anxiety in their minds.
But due to her slick detective work on ticks, Kirkland has
determined that people who live in the southeastern states
aren't contracting Lyme Disease, as was suspected, but
something else that seems to be a tamer cousin.
Between a fellowship at Duke University Medical Center and a
post in Duke's Division of Infectious Diseases, Dr. Kirkland
worked for the federal Centers for Disease Control (CDC) as an
epidemic intelligence officer. Assigned to the North Carolina
Health Department, she was put on the case of a mysterious
tick-born rash that cropped up in the middle of the state.
Ticks were running amok in an outdoor camp for girls. In two
months, 324 ticks were removed from the residents and staff and
some of the bites were followed by a circular red inflamed
ring, akin to the rash seen in people bitten by ticks infected
with the Lyme disease bacteria. Of the 12,000 cases of
suspected Lyme disease recorded by the CDC in 1995, the
majority, by far, came from northern states where the disease
is carried by the deer tick, which isn't prevalent in the
South. Yet similar rashes were also reported by physicians from
southeastern states, including North Carolina. But the CDC was
unable to isolate the microorganism that causes Lyme disease
from skin samples taken from 70 southern patients.
So the question Kirkland wanted to answer was: Is a
different kind of tick carrying Lyme disease? And, if not, what
sort of disorder is this?
First, the easy part. The ticks in question at the camp go
by the name of Lone Star because the female displays a
distinctive white spot on the back of its shell. The Lone Star
is very common in North Carolina. It is brownish-orange and
smaller than the other tick normally in residence – the dog
tick, which is large, grayish-brownish-black, and the scourge
of every pet and its owner.
But the researchers didn't know what genre of organism Lone
Star ticks at the camp might be carrying.
Ticks, as well as mites, fleas and lice, can carry
rickettsiae, which share features of both bacteria and viruses.
Like bacteria, rickettsiae have cell walls and enzymes, use
oxygen, and can be destroyed by antibiotics. Like viruses, they
can live and multiply only inside cells. In fact, after
infecting their prey, they live inside the cells lining small
blood vessels, causing the vessels to become inflamed or
blocked and to bleed.
The best known example of a rickettsiael disease is Rocky
Mountain Spotted Fever transmitted by dog ticks, which, if
untreated, produces a fever, headache, rash, and a systemic
illness that can range from mild to deadly. Lone Star ticks
have been associated with ehrlichiosis, a disease that can
produce the same symptoms as Rocky Mountain Spotted Fever, but
without a telltale rash.
As alarming as these diseases can be, only about 5 percent
of ticks shepherd such microorganisms, and infections can be
cured if a patient is given a course of antibiotics early.
Then there are spirochetal infections, such as Lyme disease.
Spirochetes are corkscrew-shaped bacteria that move by
undulating. Once introduced into the skin, the bacteria can
migrate outward and spread in the lymph or through the blood to
other organs. Untreated, the infection can involve the joints,
the nervous system and result in chronic disease.
Kirkland suspected the campers were being infected by a
spirochete bacterium, because the rash resembled that of Lyme
She led a team of researchers who set up shop at the camp.
Logs were made of all the ticks collected, and whom they were
removed from and when, and they took blood and skin samples.
They checked animals in the area for ticks and scoured the
ground for evidence. In all, 14 people in the camp developed a
rash from a Lone Star tick bite, and 10 of them developed a
mild systemic illness. They were treated with an antibiotic and
they quickly recovered. During the same period, several other
camp dwellers developed Rocky Mountain Spotted Fever or
ehrlichiosis. One person died.
Kirkland's research, published in the December 1997 issue of
the journal, Archives of Internal Medicine, solves one riddle –
it rules out Lyme disease as the cause of the infection. The
rashes sported by campers were slightly smaller and more
irregular in shape compared to the Lyme disease rash. And they
seemed to follow the bite of the Star tick, which has never
been associated with Lyme disease. And none of the 14 campers
with the rash showed any laboratory evidence of infection with
the spirochete that causes Lyme disease.
But she says it raises more questions than it answers. The
organisms that cause the rash haven't been isolated yet, and
she doesn't know if the infection, if allowed to progress,
would produce the same health problems associated with
untreated Lyme disease. Or it could be a milder relative.
One thing Kirkland is sure about, however: people living in
North Carolina, as in many parts of the country, should check
themselves for ticks if they have been walking in tall grass
and woodsy areas.