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 disease. 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.
"Ticks are ubiquitous in the Southeast and people who live here have to find a balance between being suspicious of the ticks they come across without being alarmed," she says. "In a word, be vigilant."
The above post is reprinted from materials provided by Duke University Medical Center. Note: Materials may be edited for content and length.
Cite This Page: