Campus News

New model combines ecological, immunological data to explain puzzling Lyme disease patterns

In the U.S., most human cases of tick-borne Lyme disease occur in the Northeast—with a smaller cluster in the Midwest—even though the bacteria that cause it are equally common in ticks in both regions. A new study by researchers in the Odum School of Ecology, published in the journal Epidemics, combines ecology and immunology to offer an explanation for this puzzling disparity.

The researchers, led by James Haven, a postdoctoral associate in the Odum School, used information about how Lyme disease behaves and ecological
data about ticks to create a model that sheds light on this well-documented but poorly understood pattern.

They found the timing of the tick life cycle—which appears to be driven by the local seasonal variability in temperature—plays an important role in determining which of the two types of Lyme disease thrive in a given area and how severe the disease outbreaks tend to be.

“In the Northeast, the difference between summer and winter temperatures is not as extreme as it is in the Midwest,” Haven said.

In the Midwest, tick larvae and nymphs tend to emerge at roughly the same time, while in the Northeast larvae emerge after nymphs—in some cases more than a month later.

Andrew Park, study coauthor and assistant professor in the Odum School and the College of Veterinary Medicine, said the team undertook the study because they wanted to understand how rapidly cleared types of Lyme disease survive and thrive in different areas across North America. By combining information about disease dynamics and ecological data, they were able to do just that.

“If we hadn’t taken the time to combine the tick ecology with laboratory-based disease duration data, we wouldn’t have understood what, to many people, is strictly a medical problem,” he said.