Lyme Disease Tick Adapts to Life On the (Fragmented) Prairie
Excerpted from the Science Daily ( Posted: 06/21/2011 )
ScienceDaily (June 21, 2011) — A new study offers a detailed look at the status of Lyme disease in Central Illinois and suggests that deer ticks and the Lyme disease bacteria they host are more adaptable to new habitats than previously appreciated.
Led by researchers at the University of Illinois, the study gives an up-close view of one region affected by the steady march of deer ticks across the upper Midwest. Their advance began in Wisconsin and Minnesota and is moving at a pace of up to two counties a year in Illinois and Indiana.
Today the deer tick is established in 26 Illinois counties, up from just eight in 1998, said Illinois Department of Public Health entomologist Linn Haramis. Reports of human Lyme disease cases in the state have more than tripled in the same period, he said.
“We’ve had several years in a row where we’ve had over 100 cases, up from about 30 per year more than 10 years ago,” Haramis said. “It’s not a huge increase, but it’s been steady and there’s an upward trend.”
Deer ticks are known to do best in forested areas, where they can readily move from small mammals (which provide their first meal) to moist leaf litter on the forest floor, and then to deer, on which they mate. Deer ticks do not pick up the Lyme infection from deer, said Jennifer Rydzewski, who completed her master’s degree with the study in the department of natural resources and environmental sciences at the University of Illinois.
“The deer tick will feed on a variety of mammals, birds and even reptiles,” she said. “But Borrelia burgdorferi, the bacterium that causes Lyme disease, replicates really well within white-footed mice, so white-footed mice are the main reservoir that passes that bacterium on to the immature ticks that are feeding on it.”
White-footed mice also are forest dwellers. Prior to the new study, little was known about whether, or how, Lyme disease persists in other habitat types.
To determine if Lyme disease had gained a foothold in the patchwork of forests, farms and prairies of Central Illinois, researchers trapped small mammals in Allerton Park, a 1,500-acre (600-hectare) natural area in Piatt County. They focused on four habitat types: young forest, mature forest, a flood plain and a 30-acre (12-hectare) patch of prairie surrounded by woods and agricultural fields.
The researchers removed deer ticks from the mammals they trapped and tested the ticks for Lyme disease.
They found that the immature forest and the prairie hosted the highest percentage of deer-tick-infested mammals, the highest number of ticks per mammal trapped and the highest rates of ticks infected with Lyme disease of the four habitat types evaluated.
“The highest prevalence of B. burgdorferi infection was found (in deer tick larvae) from the prairie (27 percent) followed by the young forest (15 percent), the mature forest (6 percent) and the flood plain (6 percent),” the researchers wrote.
For the complete article: http://www.sciencedaily.com/releases/2011/06/110621131328.htm