Researchers from the University of Pennsylvania and the New York Department of Health and State University of New York have conducted a study to know the origin and recent migratory history of blacklegged ticks in the Northeastern United States.

Study researchers said that the spread of the population is due to the fact that the bacteria causing the disease is thriving in areas that were once thought to be not having blacklegged ticks. In the study, the researchers have conducted genetic and phylogeographic analyses.

The researchers said that the ticks have moved into new areas through local moves. Study's lead researcher Camilo E. Khatchikian from Penn's Department of Biology in the School of Arts & Sciences said that they considered two hypotheses.

Firstly, either the considered 'new' tick populations are not new and showed an increased growth in populations. Second hypothesis is the populations have increased because of ticks moving in from other places.

In order to know their history, the researchers have evaluated the data gathered from four places in New York's Hudson River Valley between 2004 and 2009. To know the relationship between tick population and how they have changed over time, portions of the mitochondrial DNA were sequenced.

Upon assessment it has been found that ticks mainly moved in south-to-north migration events between neighboring locations. The researchers said that the ticks came to northernmost locations 14 years ago, second most northern 31 years ago and third most northern 40 years back.

"If we want to reduce tick populations over the long term, this means we have to start thinking about more sophisticated approaches", said researchers.