Nearly 40 percent of Maine deer ticks submitted to the University of Maine Tick Lab in 2019 tested positive for Lyme disease, according to the lab’s first tick surveillance annual report. A smaller percentage tested positive for anaplasma and babesia, two other common tick-borne diseases.
In addition to providing information about the prevalence of tick-borne diseases in Maine, the report gives a picture of where and when people are encountering ticks throughout the state.
“This will serve as a sort of baseline to make comparisons as we move forward, to see how fast [ticks] are spreading and establishing new populations throughout Maine,” said Griffin Dill, who manages the Tick Lab, located in the new UMaine Cooperative Extension Diagnostic and Research Laboratory in Orono.
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This is a first-of-its-kind study for Maine. With additional data points in future years, it will give researchers a clearer look at the ticks roaming Maine, the types of diseases they carry and how this could impact Maine residents. They will also be able to see how tick populations and risks vary from year to year, allowing for better predictions of tick season outcomes.
The new report summarizes information that was gathered by the lab in 2019, which is the first year that the lab accepted tick samples from the public to test for tick-borne pathogens. It’s free to send in ticks for identification. For $15, Maine residents could have deer ticks tested for causative agents of Lyme disease, anaplasmosis, and babesiosis — the three most common tick-borne diseases in Maine.
A total of 2,697 ticks were submitted to the lab in 2019. The samples came from 358 towns, including ones from each of the state’s 16 counties.
The majority of the submissions — 2,056 specimens — were identified as deer ticks, and these were tested for disease. According to the report, 759, or 38.8 percent, of the deer ticks tested positive for Lyme disease. About 8 percent tested positive for anaplasma. And about 6 percent tested positive for babesia.
American dog ticks also made up a significant portion of the submissions with 585 specimens. In addition, 37 woodchuck ticks, 10 lone star ticks, one squirrel tick and one mouse tick were sent to the lab in 2019.
These species were not tested for diseases in 2019. But in 2020, the lab plans to expand the program and start testing American dog ticks and lone star ticks for the causative agents of Rocky Mountain spotted fever, ehrlichiosis and tularemia. The lab also plans to start testing deer ticks for Borrelia miyamotoi, which is similar to Lyme disease and has been diagnosed in Maine residents.
“The woodchuck tick is a little bit of an issue in that it’s known to transmit Powassan virus,” Dill said. “Unfortunately we aren’t going to be testing for Powassan virus this coming year. It’s an entirely different type of testing that needs to be done for that.”
Collecting information from the public in this way is called “passive surveillance” and can potentially result in a bias toward certain geographic locations.
“We’re relying on people to actually find the ticks and send them in. We’re not actually going out and systematically searching the entire state,” Dill said. “That can lead to some biases in the information itself … For example, you’ll notice there is some clustering around Bangor and the Orono area. That’s where our lab is located, so it’s easier to bring in a tick around there.”
Nevertheless, Dill said that the maps generated for the report give a fairly good representation of where ticks and tick-borne diseases are found in Maine.
The report also includes information gathered from the survey that people fill out before sending in a tick for testing. This survey includes questions about where the ticks are found (often on a human body) and under what circumstances.
“We wanted to know a little bit about how ticks are behaving on the body,” Dill said. “That generated some interesting information about the difference of how ticks attach on adults versus children, which we somewhat expected.”
The data show that ticks were more frequently found higher on the bodies of children than adults. Dill believes this is because children are shorter, so ticks have less of a distance to travel to reach areas like the neck and head.
In addition, the report includes what activities people were engaged in when they encountered ticks. “Gardening-yard work” was the most common activity by far, accounting for about 38 percent of the ticks sent to the lab. “Walking” came in second, accounting for about 20 percent of the ticks.
Furthermore, the report showed when people encountered ticks in Maine in 2019. The data showed that Maine residents found the most adult deer ticks in late October and early November, with a smaller peak in April and May. Nymph deer ticks, which are smaller and younger than adult deer ticks, peaked in June and early July. And the number of American dog ticks found peaked in early summer, then dropped off.
You can learn how to submit a tick for testing at ticks.umaine.edu.
The $15 test for tick-borne pathogens will continue to be available to the public for 2020. In addition, the public can send ticks to the lab for free identification, a service that the lab has offered for several years. The lab also plans to increase field monitoring for disease-carrying ticks throughout Maine.