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Tracking the Lyme Bug's Every Move

Illness worsens as bacteria travels through bloodstream

FRIDAY, May 20, 2005 (HealthDay News) -- Scientists have gleaned new insights into how the Lyme disease bacteria invades the human body.

The finding could help lead to new targets against the tick-borne pathogen.

In their five-year study, researchers at New York Medical College tracked 213 initially untreated adults with erythema migrans -- the telltale bull's-eye rash that's the most common clinical feature of Lyme disease.

"If Lyme disease stayed in the skin it would be a completely different and rather inconsequential infection -- but it doesn't," study leader Dr. Gary P. Wormser, professor of medicine, director of the division of infectious diseases and vice chairman of the department of medicine, said in a prepared statement.

"The causative agent of Lyme disease can spread from its entry point at the tick bite site through the blood to distant sites such as the brain, heart and joints. This study answers questions that have never been answered before and raises others that will likely stimulate future studies on Lyme disease," said Wormser, who published the findings in this month's Annals of Internal Medicine.

His team sought to determine when bloodstream invasion by Lyme disease bacteria occurs, how many patients experience bloodstream invasion and which people might be most vulnerable.

Among the 213 people in the study, bloodstream invasion occurred in 93 people (43.7 percent). These people displayed more symptoms and were more likely to have multiple erythema migrans than patients without bloodstream invasion, the researchers found.

Some of the patients had no obvious symptoms of Lyme disease, demonstrating that the use of clinical features alone can't be used to determine the presence or absence of bloodstream invasion, the researchers said. Younger patients and those with a previous history of Lyme disease were somewhat protected from bloodstream invasion.

"The high rate, early onset, and prolonged duration of risk for bloodstream invasion probably explain why untreated patients with erythema migrans often develop complications distant from the tick bite location. Older patients without a past episode of Lyme disease are at particular risk," Wormser's team concludes.

More information

The Arthritis Foundation has more about Lyme disease.

SOURCE: New York Medical College, news release, May 2, 2005
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