May 2 2005
The results of a five-year study, published this week in the Annals of Internal Medicine by researchers at New York Medical College, reveal intriguing new data on the spread of the Lyme disease bacteria through the blood stream.
The ability to find the Lyme spirochete--the tick-borne agent responsible--in the blood is itself an achievement because existing methods of culturing blood were not sensitive enough to detect its presence until College researchers developed a new technique, which they used in the study.
Leading the study was Gary P. Wormser, M.D., professor of medicine, director of the Division of Infectious Diseases and vice chairman of the Department of Medicine. "If Lyme disease stayed in the skin it would be a completely different and rather inconsequential infection--but it doesn't," Dr. Wormser explained. "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."
The study followed 213 initially untreated adults with erythema migrans, the tell-tale bull's eye rash that is the most common clinical feature of Lyme disease, to determine when does blood stream invasion occur, how many patients experienced blood stream invasion and who is most vulnerable. Blood stream invasion occurred in 93 (43.7 percent) of patients in the study, who also were more often symptomatic (89.2 percent vs. 74.2 percent) and more likely to have multiple erythema migrans lesions (41.9 percent vs. 15.0 percent) than the 120 patients without blood stream invasion. However, some patients had no tell-tale symptoms at all, making the presence or absence of blood stream invasion impossible to predict with certainty based on clinical features alone. Younger patients and those with a prior history of Lyme disease were somewhat protected.
Dr. Wormser and his colleagues concluded that, "The high rate, early onset, and prolonged duration of risk for blood stream 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."