Published: June 23, 2008 New Haven, Conn. — The epidemic of Lyme disease in the U.S. is caused by a bacterium that has European ancestry, according to a new study published in Proceedings of the National Academy of Sciences that is co-authored by scientists at Yale School of Public Health and t…
New Haven, Conn. — The epidemic of Lyme disease in the U.S. is caused by a bacterium that has European ancestry, according to a new study published in Proceedings of the National Academy of Sciences that is co-authored by scientists at Yale School of Public Health and the University of Bath in England.
Some researchers had believed the Lyme disease bacterium Borrelia Burgdorferi, which is less common in Europe, originated in the United States.
Yale researchers and their
English colleagues studied the evolutionary history of the Borrelia Burgdorferi strain by examining the sequences of eight “housekeeping” genes, which are known to evolve very slowly. The researchers analyzed 64 different samples of bacterial DNA from ticks collected in the field and from infected human patients at locations across Europe and the U.S. A computer-generated evolutionary tree shows that European strains are more closely related to a common ancestor than are the North American strains,
indicating a European origin for the Lyme disease bacterium in the U.S.
The type of genetic analysis used in this study, called multi-locus sequence typing, or MLST, reveals the evolutionary history of microbes by looking at mutations in genes essential to metabolism. It has been previously used in epidemiological investigations of directly transmitted human pathogens, but this is the first time MLST has been used to study a pathogen that is transmitted to humans from wildlife through the bite of a
vector such as a tick. Since wildlife and vectors do not move as much as humans, these pathogens leave an evolutionary trail tied into their local environment.
“Understanding the evolution of pathogens is a key epidemiological tool,” said Durland Fish, professor of epidemiology and principal investigator on the Yale research team that took part in the project, funded by the National Institutes of Health. “By understanding the evolutionary history of pathogens, we can better predict their
The team in Bath was lead by Gabriele Margos of the Department of Biology and Biochemistry.
Lyme Disease, which causes more than 20,000 new cases each year in the US, is still spreading from the original outbreak in Lyme, Connecticut. The Yale/Bath team is continuing to study the evolution of the Lyme disease spirochete in Europe and North America hoping to understand how the disease is spreading and where future outbreaks will occur.