The height of the season for blacklegged tick nymphs is now. These adolescent ticks are tiny, difficult to spot on the body and have already fed once, giving them a chance to acquire the bacteria that produces dreaded Lyme disease.
According to the Maine Medical Research Center, 65 percent of the Lyme disease reports in Maine occur during this time of year. Nymphs, less than 2 millimeters in diameter, are about the size of poppy seed and can easily be mistaken for a freckle.
Alan Eaton, an entomologist at the University of New Hampshire Cooperative Extension in Durham and a state expert on ticks, avoids tick sampling during this part of the year because he feels it’s too dangerous. The nymph season starts around mid-May and continues into July and later, depending on the weather.
One of Eaton’s many tasks is identifying ticks the public brings in, which he reports to the state. He highlighted the difficulty of finding blacklegged nymphs through a recent example of a woman who dropped off a tick for identification — she found the critter hidden between her toes.
“It’s not a place where we always think to check,” he said.
Based on the anecdotal data from the samples he’s received this year, the nymph season is on par with last year, though the nymph population dropped in the last part of the season because of the moderate drought the region experienced in late June. Nymphs need a meal or moisture to stay alive. Once they’ve found a meal, they will molt into an adult and re-emerge in the fall. If they dry out, they die.
While the adult ticks have had two chances to acquire Lyme disease from feeding on hosts, they are easier to spot and feel on the body. Eaton said they also take a longer time to transfer the Lyme-causing bacteria to humans. Where it generally takes 24 hours for nymphs with the disease Lyme to transfer it to humans, it takes adult ticks about 36 hours to do so.
Lyme disease can cause a variety of symptoms, such as headaches, stiff neck and muscle and joint pain. If not caught early, other long-lasting symptoms may develop, like aseptic meningitis, encephalitis and cranial neuritis.
Last year, New Hampshire had an estimated 1,371 cases of Lyme disease with the highest number of cases in Rockingham, Hillsborough and Strafford counties. Rockingham had 456 cases and Strafford had 163. In Maine, there were 1,171 reported cases in 2015, with York County reporting 178. Eaton said Strafford, Rockingham and York counties are all good places to find blacklegged ticks carrying the disease.
A New Hampshire Department of Health and Human Service alert from late May stated that New Hampshire continues to have among the highest rates of Lyme disease in the nation and that roughly 60 percent of all blacklegged ticks sampled in the state were infected with Borrelia burgdorferi, the bacterium that causes Lyme disease.
While Lyme disease gets all the attention, blacklegged ticks, also known as deer ticks, can also carry babesiosis, anaplasmosis and Powassan virus. Last year, there were 110 cases of anaplasmosis and 53 cases of babesiosis reported in New Hampshire, and Eaton said their presence in the state is rising. The only known case of Powassan virus in New Hampshire was reported in 2013.
The most important prevention method is through daily checks, Eaton stresses again and again. Check yourself and check your children every day, especially this time of year. “If there is only one thing you do, do a daily tick check,” he said.
After that, tall rubber boots can help, as the ticks slip off the rubber. DEET-based insect repellents can also help. Tucking socks into pants can help as can wearing light-colored clothing to better see ticks crawling up clothes. Staying out of high grasses and brush is also helpful.
Last year, the New Hampshire DHHS released the “Tickborne Disease Prevention Plan,” which has a plethora of information about the disease that also outlined landscaping suggestions to help keep ticks to a minimum in the back yard. It includes ideas such as keeping children play structures in the sun and away from the woods, as ticks dry out in the sun.
The main reservoir for ticks to acquire the Lyme pathogen is from white-footed mice. Blacklegged tick larvae often feed on these mice and get the bacteria. Keeping their habitats to a minimum around homes is another strategy to help prevent Lyme infection.
Eaton said there are five things that keep Lyme alive: The spirochete that causes the disease; reservoir hosts (white-footed mice); ticks to spread the disease; other hosts to keep the population alive, such as deer and victims.
“You pull any of those out and it can easily drop,” he said.
One interesting proposed study to reduce Lyme disease may occur in Nantucket, Eaton said, which has high rates of Lyme disease. Earlier this month, according to a New York Times article, an MIT biologist proposed introducing genetically engineered white-footed mice on the island “that are immune to the Lyme-causing pathogen, or to a protein in the tick’s saliva, or both, to break the cycle of transmission,” the article states.
“It’s a really interesting alternative, but we’ll have to evaluate the risks as well,” Eaton said.