Last Friday, The Times accompanied Dick Johnson, field biologist for the Martha’s Vineyard boards of health Tick Borne Disease Initiative (TBDI), on a tick safari in Chilmark. Mr. Johnson was surveying a yard just off Tea Lane as part of a free service provided by the TBDI, which studies the Island tick population and advises homeowners how they can better defend themselves and their loved ones against ticks and the virulent illnesses that they can carry.
Of the three ticks roaming the Island — deer ticks, dog ticks, and Lone Star ticks, Mr. Johnson was particularly interested in deer ticks, specifically deer tick nymphs. By the time the nymphs reach adulthood in late summer, they will be responsible for about 90 percent of the Lyme disease contracted by humans. Most cases of Lyme disease are contracted in mid to late June, in large part because deer ticks in the nymphal stage are the size of a pinhead, or smaller.
Deer tick nymphs, the teenagers of the tick world, emerge en masse in the spring, 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 bacterium that causes Lyme disease, from the white-footed mice they cozied up with over the winter. Because they’re so small and because they excrete a natural anesthetic when they bite, deer tick nymphs are masters at avoiding detection and inflicting infection.
The up-Island towns and Chappaquiddick appear to have the highest concentration of deer ticks. Not coincidentally, they also have the highest concentration of deer. Deer are key link in the abundance of ticks because they provide a blood meal for adult ticks.
“This year in Chilmark I had my first yard with over 100 deer tick nymphs,” Mr. Johnson said. “If we have a hot, dry July, the nymphs will drop off by mid-month. If it’s a damp July, they’ll hang around until the end of the month.”
Typical symptoms for Lyme disease include fever, headache, fatigue, and a characteristic skin rash called erythema migrans. The telltale “bull’s-eye rash” only shows up about 60 percent of the time. If left untreated, the corkscrew Borrelia burgdorferi bacterium can drill itself into joints, the heart, and the nervous system.
Lyme disease is only one of the tick-borne illnesses Islanders and visitors can contract from a tick bite. Babesiosis, ehrlichiosis, spotted fever, and tularemia also lurk.
Although they are abundant, deer tick nymphs are not as plentiful as dog ticks. “I can go to some places on the Island and get 100 dog ticks in a 25-yard sweep,” Mr. Johnson said.
Lone Star ticks only recently colonized the Vineyard. Mr. Johnson has found the most dense populations in Aquinnah and Chilmark, and they appear to be growing in number. “Last year I found Lone Star ticks in about one in 10 yards. This year it’s been every other yard,” he said.
Lone Star ticks do not carry Lyme disease. According to the Centers for Disease Control, they carry Southern tick-associated rash illness (STARI), which can present with a rash similar to Lyme disease. They also carry spotted fever, which is similar to Rocky Mountain spotted fever, tularemia, and ehrlichiosis.
Unlike deer ticks and dog ticks, which are blind and wait passively for their prey, Lone Stars can see their prey and chase it. “Lone Star ticks are like super ticks,” Mr. Johnson said. “They’re really fast and very strong.”
Survey says …
Mr. Johnson’s survey method was simple — he swept the perimeter and tick-friendly areas like piles of leaf litter with his “flag,” a thrift store towel attached to a piece of doweling. After about 20 yards, he put the towel on the ground, got down on his hands and knees, and scanned it for moving specks about the size of a pinhead, sometimes smaller.
It’s an incongruous sight, a burly 6-foot, 4-inch man on his hands and knees, his long pants tucked into his socks, staring at a towel and occasionally picking at it with his large paw. “The job is tough on the knees,” he said. “That’s the hardest part.”
Looking at ticks all day can also create phantom ticks. “I scratch a lot,” he said. “I wouldn’t be surprised if people think I have fleas.”
To break up the monotony of staring at a towel for hours on end, Mr. Johnson engages in auditory birding, pointing out the songs of various birds without lifting his gaze.
To the untrained eye, the deer tick nymphs are indistinguishable from a tiny speck of dirt. But soon, Mr. Johnson began plucking them out of the towel and sticking them on a lint roller.
“You get a search image in your head after you do this for a while,” he said. By the time he was done scanning the towel from the first drag, nine deer ticks dotted the lint roller.
“I find a lot along driveways for some reason,” he said. “Leaf litter is their favorite habitat. Highbush blueberry is a good indicator for deer ticks, because they grow in damp soil. I also find a lot in the shade underneath rhododendron bushes,” he said. “Lone Star ticks seem to favor honeysuckle and bittersweet.”
Years with big acorn harvests also seem to produce more ticks, Mr. Johnson said. “They bolster the mice population, and the more mice, the more ticks survive.”
This is the sixth year Mr. Johnson has been conducting yard surveys. The five-year grant from the Martha’s Vineyard Hospital that funded the TBDI ended last year, but there was still enough money left to keep Mr. Johnson surveying through the fall.
Mr. Johnson surveys about five yards a day, depending on the size of the property. He also surveys Land Bank and Sheriff’s Meadow trails.
“I can barely keep up with demand,” he said. “Which is a good thing. It means more people are becoming more aware.” Mr. Johnson, 63, said the program has also been rewarding from a biologist’s standpoint. “The more I learn about ticks, the more I get interested in them,” he said.
Organic yard sprays appear to reduce tick numbers. “I’ve done side-by-side yards where one homeowner has sprayed and the other hadn’t; there was definitely a difference,” he said. “There are sprays you can get at the store that attach to your hose, and there are a few companies that do it here as well.”
By the end of the 90-minute survey, Mr. Johnson had collected 45 deer tick nymphs, two dog ticks, two deer tick larvae, and two larvae that required a microscope to identify. He wrote a note indicating the place and date of the survey, peeled the contact paper off the lint roller, and put it in a Ziploc bag which would eventually be sent to Sam Telford, professor of infectious diseases at the Tufts University School of Veterinary Medicine and consultant to the TBDI. Mr. Telford has been studying ticks on the Vineyard since 1994.
“I’ve got about a thousand ticks in my refrigerator for Sam right now,” Mr. Johnson said.
Mr. Johnson first met Mr. Telford in 1990 when they were both doing field work on Nantucket; Mr. Johnson was studying hermit crabs at the time. Mr. Johnson eventually moved to Martha’s Vineyard to take a job as the executive director at the Sheriff’s Meadow Foundation, which was a one-man operation at the time. The TBDI brought him out of retirement six years ago to help tackle the growing tick problem.
It appears the five-year campaign of the TBDI and MVBOH may be paying off. According to the most recent Department of Public Health (DPH) statistics, cases of reported Lyme disease in Dukes County have been trending downward. From a peak of 502 cases per 100,000 people in 2012, the numbers dropped to 423 in 2013 and 308 in 2014.
The Martha’s Vineyard Boards of Health (MVBOH) website has a trove of information about ticks, disease prevention, symptoms and treatment.
Homeowners who would like Mr. Johnson to do a tick survey of their property can email him at email@example.com or call him at 508-693-1893.