It’s tick season — time to get out the insect repellent and take other measures to avoid tick bites.

Of increasing concern is the blacklegged tick that can transmit Lyme disease and is expanding its presence in Virginia, according to a University of Richmond biologist studying its migration across Virginia.

That migration — from Northern Virginia southwestward along the Blue Ridge Mountains — matches where the biggest increases in reported cases of Lyme disease in people are occurring in the state, said Jory Brinkerhoff, an assistant professor at UR.

“Five or 10 years ago, the Lyme disease picture in Virginia was quite different than it is today,” Brinkerhoff said. “These diseases, they occur in a dynamic environment, so what was true 10 years ago might not be true today as far as where diseases are and are not found.”

Reported cases of Lyme disease in Virginia rose from 216 in 2004 to 1,307 in 2013. Numbers for 2014 are not yet final, but preliminary data from January to December 2014 show 1,167 new cases.

Brinkerhoff is lead author of a study published in October that examines the prevalence of blacklegged tick populations in Virginia and where cases of Lyme disease are increasing.

While Virginia Lyme cases are concentrated in Northern Virginia — in 2013, Fairfax County had 257 cases and Loudoun County had 168 — the disease has been found in most localities across the state, including the Richmond area. In 2013, Chesterfield County had 20 cases, Henrico County had 19, Hanover County had six and Richmond had five.

In Virginia, June and July are the months when most people diagnosed with Lyme disease first notice symptoms, according to the Virginia Department of Health. Ticks are at the nymph stage and tiny — about the size of a poppy seed — and so are easily missed when doing tick checks.

Blacklegged ticks thrive in decaying leaves on forest floors. Lyme disease is caused by Borrelia burgdorferi bacteria. Not all blacklegged ticks are infected with the bacteria.

While reported cases of Lyme disease in Virginia were pegged at 1,307 in 2013, those numbers may be a vast undercount. The federal Centers for Disease Control and Prevention said the actual number of new cases of Lyme disease occurring each year in the U.S. may be 300,000 — 10 times the approximately 30,000 cases that get reported.

For his research, Brinkerhoff, working with two UR students, did a rough measure of blacklegged tick populations in four areas of the state: Lesesne State Forest in Nelson County, Appomattox-Buckingham State Forest in the central region of the state, a UR field site in Goochland County, and at Crawfords State Forest in New Kent County.

The researchers did something called drag sampling, also referred to as flagging, for ticks. They attached pieces of cloth, in this case a light-colored square of corduroy, to a handle and dragged the cloth along 100-meter lengths of forest floor marked off by flagging tape. Every 20 yards or so, they stopped and pulled off any ticks and put them in alcohol to take back to the lab for analysis, Brinkerhoff said.

“It’s kind of low-tech, but it’s also one of the best ways to get what we call a proxy for risk,” Brinkerhoff said. “It’s a way to compare densities of ticks at different forest lots. ... We know we are not getting all the ticks at any given site, but the proportion of ticks we get should be pretty much constant at all sites, so we can essentially assess the risk of what would happen to a human walking through the same area — about how many ticks would likely climb on them and potentially bite them.”

The results showed that the test site in Nelson County had more blacklegged ticks than the other test sites, he said, and those ticks were more likely to be infected.

“It looks like those tick populations in the western part of the state are undergoing numerical expansion — so there are more ticks — and they are also spatially expanding,” Brinkerhoff said.

That fits with state Health Department data that show “a real growth of [Lyme] cases basically between Charlottesville and Blacksburg. That’s where we’re seeing the biggest increase in human cases,” he said.

Brinkerhoff, previously a post-doctoral fellow at the Yale University School of Public Health in Connecticut, said the results show blacklegged tick activity is not necessarily the same regionally.

Lyme disease is named for the city of Lyme, Connecticut, where doctors in 1975 noticed a cluster of adults and children sick with arthritis-like symptoms — swelling in the joints, fever, headaches, weakness and rash. By 1977, 51 cases had been identified, and the blacklegged tick was linked to the disease.

In Connecticut, blacklegged ticks are more likely to be found at lower elevations, Brinkerhoff said. In Virginia, blacklegged ticks were more likely to be found at the higher elevations the scientists studied. That came as a surprise — high elevation was predicted to be lower risk for ticks, he said.

Dawn Wilson, diagnosed with Lyme disease years ago and infected while doing field research as a cell biologist, thinks the finding’s implications are “just the tip of the iceberg.”

“People are getting bit in their back yard,” said Wilson, facilitator of the Richmond chapter of the National Capital Lyme Disease Association. The chapter, whose Facebook page is Richmond Lyme Alliance & Support, meets monthly and has a roster of about 200 members.

“The patients don’t know. They assume if they get a negative test, you don’t have it. They are not fully aware that the tests are so insensitive,” Wilson said.

Group member Candice McGarvey of Chesterfield said she was working in her home garden in 2009 when she got a tick bite. McGarvey did not realize she had been bitten until she noticed the characteristic bull’s-eye rash of Lyme disease. She immediately took a picture of the rash — which often dissipates before a patient can get to a doctor.

Even though testing initially came back negative, her doctor treated her with antibiotics as recommended. If testing is done too soon after infection, the results can be a false negative, implying people are not infected when they really are. Her doctor knew that could be the case and started treatment despite the negative test result.

McGarvey thought it was a done deal — treatment would wipe out the infection. So she did not associate the “bizarre” symptoms, including debilitating fatigue, weight loss and strep throat, that she had in subsequent years with Lyme disease.

She said she was retested this past February for Lyme disease and got a positive result. The test indicated she had been infected for a while, she said. She thinks it was a new infection.

“I definitely had energy problems. I chalked it up to middle age,” said McGarvey, 45. “I do wonder maybe I will finally get healthy and realize my waning energy levels were Lyme and not age at all.” She is using homeopathic treatments.

If an infected tick is removed from the skin before it’s been attached for 36 hours, bacteria transmission is less likely — that’s why checking for ticks after being outside is important.

Brinkerhoff said he continues to track tick movement.

“One of the questions we are really interested in is this spatial expansion going to continue. Is it going to lead into North Carolina?” he asked. “That’s where we are right now, tracking this expansion of human cases, expansion of tick population, and trying to make some guesses of what’s going to happen in the future.”

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