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Entomology News

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Model predicts where ticks, Lyme disease will appear next in Midwest states

By drawing from decades of studies, scientists created a timeline marking the arrival of black-legged ticks, also known as deer ticks, in hundreds of counties across 10 Midwestern states. They used these data – along with an analysis of county-level landscape features associated with the spread of ticks – to build a model that can predict where ticks are likely to appear in future years.

Black-legged ticks can carry the bacterium that causes Lyme disease, an infection that can affect the nervous system, heart and joints. The new model will help local authorities prepare for the onset of Lyme disease in their counties before the first cases appear, researchers say. They report their findings in the Proceedings of the Royal Society B.

Black-legged ticks were first found in the Midwest in the 1960s in a few counties in Wisconsin and Minnesota. The first known case of what was later named Lyme disease occurred in the Midwest in 1969. Since then, black-legged ticks have expanded into numerous counties across those states and into Illinois, Indiana, Iowa, Michigan, Ohio, Nebraska, North Dakota and South Dakota. The first Lyme disease cases in those counties track closely with the first reports of ticks.

Understanding that local health departments report new Lyme disease cases in their counties to federal officials and that the National Land Cover Database includes information about landscape features of each county, the researchers chose to use county-level data in their model. Their goal was to identify factors associated with the spread of ticks and Lyme disease to new counties.

“We used historical information to build a model that forecasts the future spread of Lyme disease in the Midwest,” said Brian Allan, an entomology professor at the University of Illinois Urbana-Champaign who led the research with former doctoral student Allison Gardner, a professor of biology and ecology at the University of Maine.

“Our model was based on a few landscape factors that were highly predictive of the spread of ticks and Lyme disease and could be used as an early warning system to forecast areas likely to undergo invasion next,” Gardner said.

Publication Date: 12/23/2020
Photo credits: L. Brian Stauffer
Editor: Diana Yates