Experts attribute the growth of tick-related illnesses to climate change and more frequent tick-human contact.
By Indi Rose, for the Community News Service
BURLINGTON — Grab your long socks, because this summer is shaping up to be the highest activity tick season the country has seen in nearly a decade, experts say.
This spring, weekly emergency room visits for tick bites in most parts of the U.S. reached their highest rates since 2017, according to the CDC. In Vermont, ER and urgent care visits have exceeded the 2017-2025 average nearly every week so far this year, but haven’t yet reached historic maximums, Vermont Department of Health data shows.
Experts attribute the growth of tick-related illnesses, such as Lyme disease, to climate change and more frequent tick-human contact.
Patti Casey, the manager of the Vermont Agency of Agriculture’s Vector Surveillance Program, which monitors tick and mosquito populations, said that this season represents a new normal for Vermont.
“I don’t think we’re going back,” Casey said.
“There are people really desperately trying to figure them out and better control them, but I think that ticks and their diseases are going to outpace the research,” she added.
Vermont has more than a dozen different species of tick, including the blacklegged tick, which is known to carry pathogens that cause Lyme disease. Also called the deer tick, the species is responsible for nearly all cases of tick-bite illnesses reported to the state, data shows.
The American dog tick, meanwhile, can carry bacteria that causes Rocky Mountain spotted fever, a potentially fatal but extremely rare disease in the region.
Casey’s team collects ticks by dragging cloths across swaths of land, aiming to identify tick and mosquito-borne diseases in the environment before they infect humans and livestock.
So far, Casey reported that American dog ticks are the most prevalent species caught in her sweeps. But the team has also found blacklegged ticks in eight towns for the first time. They include Barton, Braintree, Bridgewater, Canaan, Dover, Franklin, Orange and Readsboro.
Casey said the ticks likely already inhabited the areas but now exist in greater numbers.
The sightings in Barton and Canaan, in the Northeast Kingdom, indicate that blacklegged ticks have developed the ability to spread farther as temperatures warm, Casey said.
According to a 2018 report by the Vermont Department of Health, changes in seasonal patterns and temperature are factors in the surge in tick activity.
Mature ticks can survive in temperatures as low as 23 degrees below freezing for short periods of time by remaining dormant. But when there are warm bursts and fewer cold months of the year, ticks are more likely to be searching for food.
“If you’re a tick out looking for a meal, one warm day matters,” Casey said.
Beyond changes in weather patterns, opportunities for human-tick encounters have also increased. Research shows that the COVID-19 pandemic prompted more people to spend time outdoors, while a rise in pet ownership brought more dogs into tick habitat.
As Vermonters spend more time on trails, in forests and in their backyards, the chances of encountering ticks — and the diseases they carry — have risen alongside the growing tick population.
Additionally, ticks have been shown to prefer lounging on invasive plants, which are an active threat to Vermont forests.
Dr. Peter Hyson, an infectious disease physician at the University of Vermont Medical Center, is concerned about Rocky Mountain spotted fever, a bacterial infection that can be transmitted from dog and other tick bites. The infection is especially dangerous for people with weakened immune systems, and can be fatal. Its symptoms include high fever, rashes, muscle pain, possible seizures and more.
Researchers have no indication that the bacteria which causes Rocky Mountain spotted fever is currently present in Vermont tick populations, but cases have been detected in the region. The disease was reported in Quebec last year and has been recorded in other New England states, though it’s unclear where those patients contracted it.
As the climate changes, Hyson worries that cases could start emerging in Vermont.
“The health of the environment really is inextricable from the health of the human population,” Hyson said. “People should be aware of the impact of our actions on the environment and that those actions have blowback.”
In the meantime, public health workers are working on solutions to the tick problem, including developing vaccines.
In the 1990s, the Lyme vaccine LYMErix was shown to be effective in preventing the disease. But some patients reported side effects after receiving the vaccine, most commonly arthritic symptoms. The FDA investigated and found no evidence that LYMErix caused arthritis, but media coverage and a class action lawsuit dulled the product’s reputation. The manufacturer pulled the vaccine from the market in 2002.
More than 20 years later, clinical trials of new vaccines are under way. The new vaccine recently completed the last phase of human trials. The University of Vermont is a site for a portion of these trials, according to Hyson.
But until a vaccine is developed, the best chance of avoiding tick-borne illnesses is to take preventative measures: frequent tick checks and protective clothing.
For Lyme disease to be transmitted, an infected blacklegged tick typically must remain attached for more than 24 hours, making prompt removal an important prevention tool. Even when a tick carries a disease-causing pathogen, a bite does not necessarily result in infection.
Despite the worsening conditions, Casey said people shouldn’t be afraid of spending time outside.
“There are things you can do to keep yourself safe,” she said.