The epicenter of Maine’s tick problem is the Midcoast, according to researchers.

In six years of operation, the University of Maine Cooperative Extension tick lab has tested more than 22,000 ticks from every corner of the state. They found ticks from Hancock, Knox, Lincoln and Waldo counties are most likely to carry the pathogens that cause Lyme disease, anaplasmosis and babesiosis — the three most common tick-borne illnesses in Maine.

The Midcoast also has the most reported human cases of those illnesses and related hospitalizations.

“We don’t have a great answer as to why the Midcoast has become Maine’s tick hotspot,” said Griffin Dill, coordinator of UMaine Extension’s tick lab. “The area is quite similar to southern Maine: same climate, availability of animal hosts and habitat. … We are still trying to figure out how to explain it.”

Like southern Maine, Midcoast has diverse habitats, abundant wildlife host species and increasingly mild winters, all of which favor tick survival and pathogen transmission, Dill said. But limited on-the-ground tick surveys suggest tick abundance is no higher in Midcoast Maine than southern Maine.

Scientists like Susan Elias, a staff scientist in the vector-borne disease laboratory at Maine Medical Center Research Institute, are investigating how human behavior may differentiate Midcoast’s tick outcomes from that of southern Maine.

On a county level, age and lifestyle differences between the two could explain it, but the institute’s review of town-level pathogen, illness reporting and hospitalization data suggest that residents who live in prime tick habitat in both areas tend to be older and lead active lifestyles.

“Existing data for Maine lacks the precision to parse out with certainty the relative contribution of entomological, environmental and human behavioral risk factors responsible,” Elias and institute colleague Robert Smith concluded in a paper published last month. “Based on the available data, differences in human behaviors within the residential landscape appear most plausible and deserve further exploration.”

The tick lab study and research institute paper were published in the latest edition of the Journal of Maine Medical Center, which includes 14 research papers and case studies focused on new research and medical developments in tick-borne diseases in Maine.

The Midcoast cluster has been around for 15 years, but researchers didn’t spot it in the data because they had been comparing the total number of positive ticks and human cases reported by county instead of the per capita rate.

Total number of ticks and illnesses made the densely populated southern counties look like hot spots; looking at infection and illness rates per 100,000 residents is what revealed the Midcoast cluster, Dill said.

Ticks sent in from residents of Lincoln County had the highest rate of the bacteria that causes Lyme disease, Maine’s most common tick-borne illness, according to the tick lab study. More than half of the adult deer ticks, or 52%, tested positive. The average across all counties was 44%.

The Midcoast counties also report some of the highest human rates of Lyme disease, anaplasmosis and babesiosis in Maine. Researchers say this suggests the Hancock, Knox, Lincoln and Waldo ticks are indeed transmitting the pathogens they carry at higher rates to their human hosts.

In contrast, pathogen prevalence was lowest in adult deer ticks from Maine’s northernmost counties: Aroostook (13.6%), Piscataquis (25.8%) and Washington (31.3%).

Tick-borne diseases pose a growing public health risk in Maine as ticks extend their range, most likely due to climate change. Maine logged a record 3,218 Lyme disease cases in 2024, breaking the 2023 record of 2,943 cases, according to Maine Center for Disease Control and Prevention statistics.

Symptoms of Lyme disease include a bull’s-eye rash (although not everyone gets a rash), fever, headache, joint pain and fatigue. If caught early, Lyme disease can be treated with antibiotics.

Anaplasmosis and babesiosis are less common but cause similar symptoms to Lyme disease, although neither typically causes a rash. Unlike Lyme disease, which is rarely fatal, anaplasmosis and babesiosis can cause respiratory failure, renal failure and hemorrhage.

There were 1,284 reported cases of anaplasmosis and 309 cases of babesiosis in Maine in 2024, a 65% and 59% increase, respectively, from the year before.

With infected ticks found across the state, the Maine CDC provides year-round public education throughout the state about how to prevent tick bites, said Megan Porter, a CDC veterinarian and public health educator who focuses on vector-borne diseases.

The agency will use a sponsored social media campaign to target people in hot spots in southern and Midcoast Maine, with some Down East coastal areas added in as cases rise there, because it can easily pinpoint geographic regions and reach visitors and residents alike, Porter said.

Shorter, warmer winters are helping to boost tick populations. Even the relatively snowy 2024-25 winter likely did not knock tick populations back, Dill said, because snowpack acts as an insulator during those single-digit temperature streaks that can kill most ticks.

Climate change also explains why ticks are emerging earlier in the spring, before many people are used to taking steps to prevent tick bites, and active later into the fall. Researchers say ticks can actively hunt for hosts whenever the temperature is above about 39 degrees.

Maine Medical Association doctors say the surge in diseases spread by tick populations that no longer die off over the winter are one of the most direct links between climate change and public health in Maine, according to a survey published last year in the Maine Policy Review.

Although Maine hosts 15 tick species, it is the blacklegged tick, or deer tick, that is responsible for most of Maine’s tick-borne diseases, according to the tick lab’s latest annual report. But invasive species like the Lone Star tick also threaten the health of humans, wildlife and domestic animals.

To address these threats, UMaine Extension conducts “passive surveillance” — the study of ticks found and submitted to the tick lab by members of the public — to monitor the state’s growing tick population and its associated pathogens.

One of the lab’s goals is to identify potential risk factors that increase the risk of tick-borne illness. A majority of the ticks submitted to the public testing program were found feeding on the legs and torsos of people after doing yard work, gardening or playing on their own property.

To learn more about tick activity, the tick lab set up long-term monitoring sites last year in a dozen places across the state, including Wells, Orono and Bar Harbor, to study how soil temperature, soil moisture, air humidity and wildlife trends affect tick density and pathogen transmission.

The stations also will monitor for other disease-carrying tick species that have yet to gain a foothold in Maine but have migrated to other parts of the United States, including the Lone Star tick and the Asian longhorned tick.

If you would like to submit a tick for identification and pathogen testing, complete the online submission form at the tick lab’s website — ticks.umaine.edu — and mail your sample to the Tick Lab at 17 Godfrey Drive, Orono, ME 04473. Identification is free; pathogen testing costs $20.

To minimize risk, while in gardens and wooded areas, Porter recommends people wear light-colored clothing that covers the arms and legs and tuck pants into socks, use an Environmental Protection Agency-approved tick repellent and perform tick checks. If you’ve been in tick habitat, dry clothes on high heat for 10-15 minutes before washing.