By Rose Hoban
Ticks carrying Lyme Disease are not that big a deal in North Carolina… yet.
A study published today by Yale entomology researcher Maria Duik-Wasser generated a map of tick populations along the Eastern seaboard. She aggregated the efforts of dozens of entomologists in 37 states who wander through fields dragging pieces of cloth behind them. Young ticks, called nymphs, grab onto the cloth. From there, the scientists pick them off, grind them up and analyze what bacteria the ticks are carrying around.
From there, Duik-Wasser was able to see how many ticks in any given area are infected with Borrelia burgdorferi, the bacteria that causes Lyme disease. And Southern states weren’t that affected.
“The real concentration is in the Northeast, also near the western Great Lakes,” she said.
Ticks in North Carolina
Lyme is carried by little ticks called Ixodes scapularis, more commonly known as the black legged tick. Duik-Wasser and her co-authors concluded that in addition to being rare in North Carolina, the Ixodes scapularis living in here are just not into biting humans.
“They feed more on skinks, lizards and other reptiles,” Duik-Wasser said. “And they don’t tend to bite people as much.’
“It’s highly variable,” said Charles Apperson, professor of public health entomology at NC State University in Raleigh. “We do have nymphs in NC that are infected with Borrelia burgdorferi.”
Apperson said there are some cases of Lyme Disease in North Carolina, but it’s not like the number of cases in the Northeast, were a total of about 28,000 cases in New England and the Mid-Atlantic states in 2009 (the most recent year for available statistics). North Carolina had 417 cases in 2010 (the most recent year statistics are available).
Ixodes scapularis are just not as common as other ticks, like the lone star tick, that carries Rocky Mountain Spotted Fever, Apperson said. He’s currently involved in a study looking at forestry workers in Western NC where he collected samples from the clothes of about 140 workers last year.
“Ninety-nine percent of the samples we got were of lone star ticks,” Apperson said.
On the move
There is evidence the Ixodes scapularis are headed south, said Duik-Wasser. Most of her data come from between 2004-07. Since then, researchers at the University of Richmond, in Virginia, have found more human-biting black legged ticks.
“You could consider the map we’ve produced to be a baseline map, but at the edges they’re expanding” she said. “The front is probably expanding in several places, including in Virginia, and could eventually get to North Carolina.”
“The map should create an interest in doing more research and surveillance at those areas,” Duik-Wasser said.
North Carolina used to have a tick-disease surveillance program, but it was eliminated in the last state budget.
Duik-Wasser also said that wherever she found populations of infected Ixodes scapularis, about 20 percent of the ticks were infected wtih B. burgdorferi. That’s the threshold cited by the Infectious Disease Society of America, which recommends doctors prophylactically treat for Lyme Disease when patients living in areas that have populations of I. scapularis arrive complaining of a tick bite.
“Now we know that most areas with Ixodes will have more than 20 percent of them carrying B. burgdorferi,” said Duik-Wasser. “It’s just that no one went out and collected the ticks and tested them before.”
Tips for avoiding tick bite:
- be aware when out in the woods or in areas with lots of leaf litter
- tuck in your clothes when in a tick affected area, especially tuck pants into your socks
- use insect repellant on clothing and on exposed skin
- check skin carefully after being outside, especially in skin creases, such as underarms and between legs
(Note, the headline for this story was changed to better reflect that Lyme Disease, while present in North Carolina, is not as likely as in other, more heavily affected states.)