Higher tick populations or not, take precautions against Lyme disease

UNIVERSITY PARK, Pa. — Recent media reports have suggested that tick populations in Pennsylvania may be particularly high this year, leading to an increased risk of Lyme disease in the state.

Although it is unclear whether the number of ticks actually is higher this spring— and if so, why — it nonetheless always is a good idea to take precautions to avoid ticks and the diseases they can transmit, according to entomologists in Penn State's College of Agricultural Sciences.

"Some people believe a perceived increase in ticks can be blamed on a mild winter, an early spring, certain precipitation patterns, or a large crop of acorns that leads to an overabundance of mice that host ticks," said Steven Jacobs, senior extension associate in entomology. "However, some of these theories have little scientific basis, and most scientists agree that nature is too complex to attribute a rise or fall in the tick population to any one factor."

Joyce Sakamoto, a research associate in entomology who studies tick biology, said the impression that tick populations are higher this spring may have come from the fact that ticks emerged earlier than usual from winter dormancy.

"The number of ticks I'm finding in Centre County is comparable to previous years," she said. "But I did start seeing active adult ticks earlier than usual — in February — both this year and last year."

Sakamoto noted that between 40 and 60 percent of the ticks she tests carry the Lyme disease pathogen, though that doesn't necessarily mean all of them are capable of transmitting the illness, she explained.

Whether there's been a spike in ticks this year or not, there's no question about the long-term trend. "Fifteen or 20 years ago, the ticks that carry Lyme disease were rare in many Pennsylvania counties, but unfortunately that has changed," Jacobs said. "Today, they are found in all counties in the state."

Sakamoto added that public awareness of ticks also has increased with growth and development in Pennsylvania. "We keep expanding into habitats where ticks are found," she said. "And as that continues, we need to change our behavior to avoid them."

Even though ticks can transmit a variety of pathogens, it's no secret why Lyme disease gets the most attention — Pennsylvania leads the nation in the number of confirmed cases.

Lyme disease can cause a variety of symptoms, including a bull's-eye-like rash, fever, stiff neck, muscle aches and headaches. Left untreated, victims can suffer facial palsy, arthritis and even paralysis. It normally is treated with antibiotics, but if not caught early, recovery can be slow and difficult.

The primary vector of the Lyme disease bacterium is the blacklegged tick — often called the "deer tick." Adult ticks can be active from fall through spring if temperatures remain above 28 F. Ticks in the nymphal (immature) stages are active in May, June and July.

Nymphs will attach to mice, chipmunks, birds and other small animals. Adults typically attach to white-tailed deer or other large mammals. While awaiting a suitable host, the ticks usually are found on leaf litter or low branches in brushy, wooded areas.

 
Blacklegged ticks to scale
Image: Joyce Sakamoto
 

"The larval and nymphal stages of the tick are no bigger than a pinhead," Jacobs said. "Adult ticks are slightly larger. Research in the eastern United States has shown that ticks most often transmit Lyme disease to humans during the nymphal stages. That's probably because nymphs are so small they go unnoticed on a person's body, meaning they typically have more time to feed and transmit the infection before they are detected."

Jacobs recommends avoiding tick-infested areas such as woods with a high deer population, especially in May, June and July when the nymphs are active. And he urges those who do go afield to take the following precautions when they are going to be in brushy areas:

— Wear light-colored clothing so that ticks can be spotted more easily.

— Spray insect repellent containing DEET on clothes and on exposed skin other than the face, or treat clothes — especially pants, socks and shoes — with permethrin, which kills ticks on contact.

— Thoroughly examine yourself for ticks when returning from the woods.

"Be especially vigilant near perimeter areas of tick habitat, such as the edge of woods and along paths and trails," Sakamoto said. "Ticks can sense carbon dioxide, heat, vibration and chemical cues left by other ticks, and there's evidence that they may be more concentrated in areas where they're more likely to encounter potential hosts."

Also, know the signs of Lyme disease and see your doctor if symptoms develop, Jacobs said. "If a tick is found attached to a person, it should be removed by carefully grasping the tick with tweezers as close to the skin as possible and pulling straight back with a slow, steady force. Avoid crushing the tick's body."

He said a tick can be identified by placing it in a small vial filled with rubbing alcohol and taking it to a county office of Penn State Extension.

To learn more about blacklegged ticks and Lyme disease, visit the Penn State Entomology Department's website.

Contacts: 
Last Updated June 12, 2017