The Butler Eagles reports Monday that Butler County, about 20 miles north of Pittsburgh, reported 482 cases in 2010. That's the most recent year available.
By comparison, neighboring Armstrong County—which is also largely rural—had just 146 cases that year while two other neighboring counties, Allegheny and Beaver, had 63 and 14 cases, respectively.
The disease is caused by bacteria carried by infected blacklegged ticks which pick it up from drinking the blood of infected mice. Those ticks generally make contact with humans by first latching onto deer or other animals.
Health department spokeswoman Holly Senior says officials "cannot say for certain" why Butler County has experienced the high rate of cases.
Information from: Butler Eagle, http://www.butlereagle.com