Tick spread affects rise in Lyme disease


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.

Gaining ground. “We’re seeing blacklegged ticks from areas where previously none had been reported,” said 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 said.

“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.”

Name change. 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.

More Lyme disease. “In 1990, there were fewer than 700 new cases of Lyme disease in Pennsylvania,” he said. “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 said. “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.”

Possible tick hosts. 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 said. “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.”

Be on alert. 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.”

Avoiding tick-borne disease

UNIVERSITY PARK, Pa. – Steven Jacobs, extension entomologist in Penn State’s College of Agricultural Sciences, offers these tips for avoiding tick-borne diseases, such as Lyme disease and Rocky Mountain spotted fever:

* Avoid high-risk (brushy, wooded) areas and trails, especially in April through July.

* If you are planning to be in a high-risk area, wear light-colored clothing so you can more easily detect dark-colored ticks.

* Check your clothing for ticks every few minutes.

* Wear long-sleeved shirts and long pants tucked into socks.

* Use a tick repellent containing “DEET” on your skin and clothes, unless you have a known allergy to this compound.

* Inspect your clothes and body carefully after returning from high-risk areas.

* Inspect pets if they have been in a high-risk area. On dogs and cats, ticks often are found around the face and ears.

Many shampoos, sprays and dusts are available to eliminate ticks on pets. Tick collars are less effective, but are helpful as a repellent.

* If you find a tick on a person or animal, remove it by carefully grasping it at the mouthparts with fine point tweezers and firmly pulling it off.

Learn more. To learn more, contact your county office of Penn State Cooperative Extension or your local health department, or visit the Web at www.ento.psu.edu/Lyme/default.htm.

Get our Top Stories in Your Inbox

Next step: Check your inbox to confirm your subscription.