HOUSERVILLE, Pa. — Pennsylvania leads the nation in Lyme disease cases, and the continued development of forested areas increases people’s risk of being bitten by the species of tick that transmits the illness. When forests — where black-legged ticks thrive statewide — are fragmented to make room for roads, oil and gas sites, housing developments, or shopping centers, ticks have fewer available hosts and are more likely to bite humans.

The commonwealth had an estimated 16.6 million acres of forest land in 2019, according to the most recent data. That’s down from 16.9 million in 2014, with nearly half of the loss due to residential and commercial development. The western and eastern parts of the state saw the most forest land lost, reporting a 2% decline, and accounted for more than half of the state’s Lyme disease cases in 2022.

Environmental experts think more elected leaders should consider how forest fragmentation creates other risks, especially before green-lighting projects that come before local governing boards. And because tick season is getting longer due to warmer temperatures year-round, residents statewide are more vulnerable to contracting Lyme disease and other tick-borne illnesses.....

Pennsylvania had the highest incidence rate of Lyme disease nationwide in 11 of the past 12 years, according to data from the Centers for Disease Control and Prevention. The black-legged tick, also called a deer tick, is Pennsylvania’s most common species, and it is the only one that transmits Lyme disease when it feeds. The illness can cause flulike symptoms and lead to more severe effects if left untreated. Black-legged ticks can also spread the Powassan virus, also called the deer tick virus, which attacks the central nervous system and can be fatal in extreme circumstances.