The riskiest time of the year for contracting Lyme disease is now, experts say.
Lyme disease is the most prevalent vector-borne disease in the United States. An estimated 300,000 people contract it every year, and as many Islanders know, we live in a hot zone of the epidemic.
As winter finally loosens its icy grip, deer tick nymphs, the teenagers of the tick world, emerge en masse, hungry for the blood meal that will propel them to adulthood later in the summer. Approximately 30 percent of these nymphs have contracted Borrelia burgdorferi, the bacteria that causes Lyme disease, from the white-footed mice they cozied up with over the winter. Because they’re so small, roughly the size of a poppy seed, and because they excrete a natural anesthetic when they bite, deer tick nymphs are masters at avoiding detection. By the time these terrible teens reach adulthood in late summer, they will be responsible for about 90 percent of the Lyme disease contracted by humans.
Defense is key
“Spring and early summer is the time to use every weapon you have,” tick expert Dr. Sam Telford of Tufts University told The Times in a recent conversation. Mr. Telford has been studying ticks and tick-borne diseases on Nantucket and Martha’s Vineyard for more than 20 years. He’s never been infected with a tick-borne illness.
For defensive weapons, Mr. Telford recommends using a DEET based repellent, wearing long sleeves and long pants and treating a set of clothes, including socks and shoes, with permethrin. Light colored clothes will help make the diminutive nymphs more visible. “Spray the clothes with permethrin until they’re saturated then leave them in a cool dark place to dry,” he said. “Then you’re good to go for the rest of the summer. It’s perfectly safe. Permethrin is the active ingredient in delousing shampoos. It’s not a repellant, but it’s even better, because in three hours, any tick that touches you will be dead.” Mr. Telford added that permethrin is safe on humans and dogs, but not for cats.
A recently released two year study from the University of North Carolina determined that outdoor workers using permethrin treated clothes had 80% fewer tick bites than those who didn’t.
Permethrin can also be used to make tick tubes — cardboard toilet paper tubes stuffed with permethrin saturate cotton balls. White-footed mice use the cotton to line their nests and any ticks that cozy up to them next winter will die. According to recent information from the American Entomological Society, deer tick larvae don’t have adverse affects on white-footed mice, but in fact they have a symbiotic relationship — the study found male mice with large tick loads were more likely to survive the winter. Breaking up this relationship with tick tubes can save countless cases of Lyme disease in the future. Mr. Telford recommends placing tick tubes every 15 feet along any areas that border on tick habitat, like scrub, woods or stone fences, and repeating the process in the fall.
Why Martha’s Vineyard?
The confluence of several factors, some of them man-made, make the Vineyard a hotspot for tick-borne illnesses. “Part of the reason ticks are so bountiful on the Island is the lack of extreme temperatures and lack of predators,” Mr Telford said. “In New England, we let pastures go to forest, which changed the fauna all to the tick’s advantage. We helped them because more people live in forest to be close to nature, and people are being lazy about leaf litter.”
Bearing out Mr. Telford’s point, last week, the Center for Vector-Borne Disease at the University of Rhode Island released a study that concluded, after examining 14 years of tick surveillance and corresponding weather data, that moisture, specifically in leaf litter, is a major factor in predicting deer tick population.
“If it’s a rainy and damp spring, it’s all the more reason to be vigilant about removing leaf litter and to spray the perimeter of your property, especially if you live, like many Islanders do, in a wooded area,” Mr. Telford said. “Spraying is not a bad word. The sprays are much more environmentally friendly than they were ten years ago. Pyrethroids aren’t harmful to humans. If you’re having grandkids or a wedding in June, you should seriously consider spraying your yard.”
Islanders take note — permethrin spraying on Martha’s Vineyard requires an applicator’s license.
Another reason the Island is teeming with ticks is the white-tailed deer population, the primary food source for adult ticks. “There’s no question that deer density has a direct correlation with tick-borne diseases,” Mr. Telford said. “And deer density on the Vineyard is among the highest in the state.”
Last August, at a presentation sponsored by the Martha’s Vineyard Boards of Health Island-Wide Tick Borne Illness Prevention Program (MVBOH), Thomas Millette, professor at Mount Holyoke College, gave the results of a deer density study conducted during the winter of 2012-2013, done by criss-crossing the Island with a thermal imaging camera. “Once we had the answers, I was shocked,” he said. “The Island has an average of over 50 deer per square mile.”
The Massachusetts Division of Fisheries and Wildlife preliminary deer harvest data for the 2013 season showed Island hunters took 713 deer, up significantly from the 2012 tally of 610 deer.
On Tuesday, Mr. Millette shared his preliminary findings from this winter’s study with The Times. It appears that neither hunters nor cars made a dent in the deer population. “The number of deer we saw this past winter is virtually identical to last winter, within four or five deer,” he said.
Neither study Mr. Millette conducted included deer-rich Chappaquiddick because ground temperatures weren’t cold enough to give the contrast needed to confirm the presence of a warm-blooded deer.
Ultimately, daily tick checks from now until the end of summer are the best defense against Lyme disease and other tick-borne illnesses like babesiosis, which goes in tandem with Lyme about 10 percent of the time.
According to the New England Journal of Medicine, a single dose of doxycycline administered within 72 hours of a tick bite reduces the risk of Lyme disease by 87 percent.
“Halfway through the time of feeding is when the tick starts to spit infectious material into the host,” Mr. Telford said. “If you pull a nymphal deer tick off within 24 hours, there’s a very good chance you won’t get infected. An adult tick is easy to spot and it takes seven days to feed. Chances are pretty good you’ll find it before three days pass. And as the CDC has said, taking two tablets of doxycycline after recognizing a tick bite dramatically reduces chances of infection.”
Mr. Telford said a major asset the Vineyard has in the battle against Borrelia burgdorferi is the Martha’s Vineyard Boards of Health website and he urges all Islanders to visit it. “It’s one of the best websites in the country,” he said. “I’m delighted Mike Loberg is running it.”