Ticks capable of carrying the bacterium that causes Lyme disease have been slowly migrating along rivers in the Midwest, a trend that may help predict future areas at risk for the disease, say researchers from the University of Illinois, Urbana.
They report their results today at 50th Annual Meeting of the American Society of Tropical Medicine and Hygiene in Atlanta.
"The movement of the ticks along riverbeds in Illinois, combined with the existence of animals capable of serving as hosts to both and the bacteria can be seen as a harbinger of the migration of Lyme disease in the Midwest," says M. Roberto Cortinas, a research associate at the university's College of Veterinary Medicine and the presenting author on the study.
Ixodes scapularis, the tick that carries Lyme disease was first seen in the Midwest in Wisconsin in the early 1970s. By the late 1980s researchers began to observe the tick moving south. By 1990, when the University began tracking its migration, I. scapularis had been found along the Northern Mississippi River.
The researchers track the movement of the ticks through a number of methods. In the beginning, they focused on deer hunting season, collecting ticks from animals brought in by hunters and recording information on where the hunters found the deer.
More recently they have employed other methods including dragging, in which a piece of cloth is dragged over vegetation to collect ticks, and trapping mice.
Cortinas' research, which he began in the late 1990s, is founded on the tick risk map developed for Wisconsin and northern Illinois by Dr. Marta Guerra, now a CDC EIS officer. The research focuses on the migration of the along the Illinois River, which merges with the Mississippi River just north of St. Louis. The ticks appear to be migrating south-southwest, following the river towards the Mississippi.
So far they have been collected as far south as Peoria County.