Discovery of a lyme disease bug clone may explain disease spread

Benjamin Luft, M.D., Professor of Medicine, Stony Brook University Medical Center, and colleagues discovered that a certain clone of Borrelia burgdorferi, the spirochete that causes Lyme disease, appears to be the most common strain causing Lyme disease in North America and Europe, and may account for the increase in cases for the past 20 years. Their investigation and findings of the ospC-A clone are reported in the July 2008 issue of Emerging Infectious Diseases.

According to Dr. Luft, Lyme disease is the most common vector-borne disease in the United States with more than 20,000 cases reported annually. While B. burgdorferi is the primary pathogen in the United States, clones of the pathogen are known to cause major disease. The ospC-A clone was one of the first strains ever identified.

In “Wide Distribution of a High-Virulence Borrelia burgdorferi Clone in Europe and North America,” Dr. Luft and colleagues detail various methods of genetic testing of 68 B. burgdorferi isolates from Europe and North America. Based on the findings of their tests, the researchers concluded that the ospC-A clone dispersed rapidly and widely in the recent past and in both regions of the world.

“I believe this discovery will make an important contribution since it identifies an identical and high virulence clone of Borrelia in both Europe and North America,” said Dr. Luft. “This may explain the recent spread of Lyme disease in North America.”

The researchers report that the isolates of the clone were prevalent on both continents and uniform in DNA sequences, which suggests a recent trans-oceanic migration. More specifically, they explained: “The European and North American Populations of B. burgdorferi sensu stricto have diverged significantly because of genetic drift. Plasmid genes evolved independently and showed various effects of adaptive divergence and diversifying selection…genetic variation within the two continents contributed to most of the total sequence diversity, which suggests recent common ancestry, migration, or both, between the European and North American populations.”

(Source: Emerging Infectious Diseases: Stony Brook University: July 2008)