UNIVERSITY PARK, Pa. -- Blacklegged ticks are on the move in Pennsylvania. And their spread has coincided with an increase in reported cases of Lyme disease in the past few years, says an expert in Penn State's College of Agricultural Sciences.

"We're seeing blacklegged ticks from areas where previously none had been reported," says Steven Jacobs, extension entomologist, who oversees the entomology department's Insect Identification Laboratory.

"Fifteen years ago, these ticks were mostly limited to the southeast corner of the state, the northcentral region around the Allegheny National Forest and the Presque Isle peninsula in Erie," Jacobs says. "Now they seem to be established in more areas of central, western and southeastern Pennsylvania. In fact, the vast majority of counties have at least a small, localized population of ticks."

Blacklegged ticks for several years were known as deer ticks in the northern United States, until scientific studies confirmed that deer ticks were in fact smaller versions of the blacklegged ticks common in the South, and not a separate species.

The apparent increase in the tick's range is a concern because of the role it plays in spreading the bacteria that causes Lyme disease, a neurological disorder that can cause a variety of symptoms, including a bullseye-like rash, fever, stiff neck, muscle aches and headaches. Left untreated, victims can suffer facial palsy, arthritis and even paralysis. The disease normally is treated with antibiotics, but if not caught early, recovery can be slow and difficult.

Lyme disease accounts for more than 90 percent of vector-borne disease cases in the United States, according to Jacobs. "In 1990, there were fewer than 700 new cases of Lyme disease in Pennsylvania," he says. "In 2000, the number of cases was more than 2,300, an increase of more than 300 percent. Pennsylvania now ranks third in the nation in the number of new cases per year.

"It's unclear whether there's a direct relationship between the tick's spread and the increase in disease," Jacobs says. "The increase could be partially due to increased public awareness and better diagnosis. But I suspect that because the ticks are found in more places, more people are coming into contact with them and contracting the disease."

To survive and thrive, blacklegged ticks need appropriate hosts. The adult ticks often are found on white-tailed deer, and nymphal stages will attach to mice, chipmunks, birds and other small animals. While awaiting a suitable host, the ticks usually are found on leaf litter or low branches in brushy, wooded areas. Regions such as southeastern Pennsylvania -- with deer populations that are concentrated but have limited mobility due to surrounding development -- provide prime tick habitat.

"Blacklegged ticks can be found on many bird species," Jacobs says. "Because of their migratory paths, birds may transport ticks to new areas along or east of the state's mountain ranges. Ticks also can hitch rides with travelers and their pets, particularly on 'working' dogs that are taken into the field for hunting or show field trials."

With blacklegged ticks spreading into many areas of the state, Jacobs urges continued caution. "It's more important than ever that people take steps to avoid coming into contact with ticks, especially if they plan to be in high-risk areas," he warns. "Also, know the signs of Lyme disease and see your doctor if symptoms develop."

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EDITORS: Contact Steven Jacobs at 814-863-3963.

Contact: Chuck Gill cdg5@psu.edu 814-863-2713 814-865-1068 fax