Researchers at the University of Illinois are studying the steady march of deer ticks across the upper Midwest, which is moving at a rate of up to two counties a year in Illinois and Indiana, a UI release said Tuesday.
The tick is established in 26 Illinois counties, up from just eight in 1998, Illinois Department of Public Health entomologist Linn Haramis said, and reports of human Lyme disease cases in the state have more than tripled in the same period.
To determine if Lyme disease had gained a foothold in the patchwork of forests, farms and prairies of Central Illinois, researchers focused on four habitat types: young forest, mature forest, a flood plain and a 30-acre patch of prairie surrounded by woods and agricultural fields.
Deer ticks had managed to gain a foothold in all of the varied habitats, not just forested areas previously thought of as their main habitat, researchers found.
"The landscape of Illinois, especially the northern and central area, is very fragmented with agricultural and other development, so there aren't really big continuous areas that are forested," researcher Jennifer Rydzewski said. "And so maybe these ticks are finding new habitats to establish themselves in because of the lack of previous habitats."