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What’s Behind a Recent Uptick in Lyme Disease?

Adult_deer_tickSummer is finally here and for many in the Philadelphia area, that means day hikes along the Wissahickon Creek, picnics in Fairmount Park or maybe a week-long camping trip in New Jersey’s Pine Barrens. While those activities are all great options to get away while getting in touch with the Henry David Thoreau inside each of us, they all also come with certain health risks to be aware of, including the possibility of picking up the dreaded ticks and the diseases they can transmit.

A new report from the Pennsylvania Department of Health shows a 25 percent increase in Lyme disease cases across the state in just one year, from 2013 to 2014. What, exactly, is behind that uptick?

The report suggested the increase is largely due to better education and awareness of the disease, and in turn, more identification of it in patients who are alert to the potential symptoms, which makes sense. Lyme disease has historically been very difficult to diagnose and the more vigilant we all are when it comes to getting mystery fevers checked out, the fewer Lyme disease-positive people will go undiagnosed. The report also says Pennsylvania doctors are doing a better job of reporting new Lyme diagnoses to the state.

Anne Norris, MD, an associate professor of Infectious Diseases at Penn, said those suggestions are apt to be a factor in the rising caseload, but that it’s very likely that more Pennsylvanians are actually becoming infected, as well. Norris said that the blacklegged tick (also known as the deer tick) and Borrelia burgdorferi, the bacteria that causes Lyme disease which ticks sometimes carry, were once found only in the eastern part of the state, but have spread in recent years to all 67 counties in Pennsylvania.

New research by Penn’s Dustin Brisson, PhD, an associate professor of Biology and director of Evolution and Ecology of Disease Systems Laboratory, found just that – blacklegged ticks have migrated from established populations to colonize areas where they weren’t found previously.

Not only are the ticks spreading across the state, but they are also found in places you maybe wouldn’t have predicted in the past. Norris said that “fractured forests,” small swaths of parkland or trees in populated cities or towns, are believed to be responsible for some of the rise. She said those bits of land have fewer predators to hunt white-footed mice, the preferred animal host for ticks which can carry the disease.

Humans aren’t alone when it comes to Lyme disease risk. For instance, about 90 percent of horses in the Mid-Atlantic region show evidence that they’ve been exposed to the disease. Fortunately, most will never show clinical symptoms of the disease, but a small percentage will.

Out in Kennett Square, Penn Vet’s New Bolton Center recently began offering a new program to test horses for the disease. Those interested can schedule an appointment to transport their horse for a daylong visit and clinical staff will check the horse for any symptoms, including lameness, neurological or ophthalmological symptoms, and a team of specialists will discuss treatment options if a horse shows signs and tests positive for the disease.

Laura Johnstone, BVSc, MVSc, a veterinary resident in Internal Medicine at the New Bolton Center, said horse owners should be on the lookout for difficulty breathing and eating, collapse, muzzle tremors, changes in behavior, eye inflammation, and neck stiffness.

Lyme disease exposure is also prevalent in our smaller four-legged friends as well, but progress is being made there. Meryl Littman, VMD, a professor of Medicine in the University of Pennsylvania School of Veterinary Medicine, said the numbers of Lyme disease infected dogs may actually be on the decline. She attributed that fact to ongoing efforts to educate dog owners about the disease and encourage them to use tick prevention.

There are several options when it comes to tick prevention in dogs, ranging from topical solutions to a chewable medication which kills both fleas and ticks to a medicated collar which can keep ticks away for eight months before needing a replacement.

Fortunately, as in horses, Lyme disease rarely shows its head through any clinical signs. However, Lyme-positive dogs do let health professionals know that Lyme-positive ticks are in the area, helping them prepare for the disease.

Dr. Littman said that while there is a vaccine for Lyme disease in dogs, its use is up for debate because it’s not entirely effective and requires many booster shots. In addition, there are other diseases ticks can transmit in our area, so prevention of tick bites is still warranted.

What does this mean for casual outdoorspeople? It calls for keeping up the prevention efforts whenever you’re out and about in nature. Before heading out onto the trail, apply DEET-containing insect repellent, and once you’re hiking, try to stay in the middle of the path and out of brush and tall grass. Once you get home, conduct a thorough exam (including behind your ears, behind your knees and other easy-to-forget spots) to see if any ticks found their way onto your body.

After hiking, should you come down with a fever or spot a circular rash, head to the doctor to get checked out. Lyme disease can be tough to diagnose, but Dr. Norris says after it’s spotted, antibiotics can cure more than 90 percent of patients.

And don’t let the sometimes scary facts about Lyme disease keep you from enjoying the great outdoors. Get out there and hit the trails -- just be sure to bring your DEET.


Photo credit: U.S. Department of Agriculture

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Views expressed are those of the author or other attributed individual and do not necessarily represent the official opinion of the related Department(s), University of Pennsylvania Health System (Penn Medicine), or the University of Pennsylvania, unless explicitly stated with the authority to do so.

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