In Maine, the threat is growing.
Fourteen tick species have been found in the state. Of those species, two pose significant health threats — one to humans and another to one of Maine’s most iconic animals.
Researchers at the University of Maine — in the College of Natural Sciences, Forestry, and Agriculture; Climate Change Institute; and University of Maine Cooperative Extension — are studying the arachnids and the diseases they spread in an attempt to better protect the health of people, animals and the environment.
The deer tick or blacklegged tick (Ixodes scapularis) is responsible for the majority of tick-borne illnesses affecting humans and domestic animals in Maine. The winter tick or moose tick (Dermacentor albipictus) prefers ungulate hosts, including moose, whose population is under attack as a result of the blood-sucking pests that latch on by the tens of thousands to a single animal.
Cases of Lyme disease, the most common tick-borne disease, reached a high of 1,485 in 2016, according to preliminary data from the Maine Center for Disease Control and Prevention (CDC).
“Those reported cases are believed to be only a small fraction of the actual cases,” according to Griffin Dill, an integrated pest management specialist with UMaine Extension. “It’s thought that it’s a tenfold difference, so 1,000 cases is actually more like 10,000 cases.”
The disease is caused by a bacterium (Borrelia burgdorferi) that’s transmitted by the bite of an infected deer tick. Ticks don’t hatch carrying the disease, but contract it in the larval stage by feeding on an infected rodent, according to Dill. The ticks then transmit the disease to animals and humans during the nymphal and adult stages.
Early Lyme disease symptoms can include a bull’s-eye rash, fever, headache, joint and muscle pain, and fatigue. The disease is easiest to treat with antibiotics in the early stages. If left untreated, it can lead to arthritis; neurological problems, including numbness, pain, facial paralysis and meningitis; memory and concentration difficulties; or heart inflammation. In rare cases, Lyme disease can be fatal, according to the Maine CDC.
Dill says an increase in deer ticks began to appear in southern Maine in the late 1980s and early ’90s. Since then, the pests have increased their population in southern Maine, as well as their distribution statewide. Deer ticks have been found in all 16 counties and as far north as Madawaska, according to Dill.
Even though ecologists predicted the dry conditions of 2016 would reduce Maine’s tick population, the overall incidence of Lyme disease hit a record high. According to the UMaine report “Maine’s Climate Future: 2015 Update,” the spread of Lyme disease has been linked to temperatures that make habitat more suitable for deer ticks and their hosts.
Other tick-borne diseases, including anaplasmosis and babesiosis, also have been increasing in the state. Preliminary Maine CDC data for 2016 reported 372 confirmed and probable cases of anaplasmosis, up from 186 in 2015; and 82 cases of babesiosis, up from 56.
Anaplasmosis is a bacterial disease that can infect white blood cells. Symptoms of anaplasmosis include fever, headache, malaise and body aches. Babesiosis is a potentially severe disease that can infect red blood cells. Signs of babesiosis usually range from no symptoms at all to extreme fatigue, aches, fever, chills, sweating and anemia, according to the Maine CDC.
UMaine Extension operates the only tick identification program in the state. John Rebar, executive director of UMaine Extension, says the free service is provided as a more affordable and faster option to give people a peace of mind sooner than if they sent a tick out of state. The program also adds to UMaine Extension’s surveillance and research efforts.
Tick identification in Maine was first provided by the Maine Medical Center Research Institute’s Vector-borne Disease Lab in Scarborough, which offered the service for 25 years. In 2014, the center eliminated its program due to funding concerns and turned it over to UMaine Extension.
“We thought it was a very important service to offer,” says Dill, who has taken on coordination and expansion of the UMaine Extension tick identification program.
Since the program began, it has averaged about 275 tick identifications per year, Dill says.
UMaine Extension staff can tell clients what type of tick was submitted, as well as the common hosts and diseases that species can carry. However, the lab does not currently test for disease-causing organisms.
UMaine’s new Plant, Animal and Insect Laboratory, slated to open by early 2018, will include a Biosafety Level 3 (BSL-3) area that will allow for safe screening of blood-borne pathogens, such as tick-borne diseases. UMaine Extension hopes to offer pathogen testing for Lyme, anaplasmosis and babesiosis at a cheaper rate than out-of-state services, which can cost around $50, according to Dill.
The BSL-3 area will be a biocontained environment, according to Anne Lichtenwalner, a UMaine professor, veterinarian and director of the Animal Health Laboratory, which also will be relocating to the new facility.
One of Lichtenwalner’s major research initiatives is monitoring the health of Maine’s moose. For about seven years, the Animal Health Lab has been working with the Maine Department of Inland Fisheries and Wildlife (IF&W) to study moose survival rates and mortality sources.
The lab is part of a multiyear study assessing the health of the animal in Maine, New Hampshire and Vermont. Since 2014, IF&W has fitted 286 Maine moose with GPS collars, which enable biologists to track movement, as well as receive messages if a moose dies, according to Lee Kantar, state moose biologist.
When the moose are collared in January and February, IF&W biologists collect fecal, hair and blood samples; count parasite loads; and do a general assessment. Researchers at the UMaine Animal Health Lab then process, analyze and store the samples.
“It’s IF&W’s procedure; we provide the service and help interpret the results,” Lichtenwalner says.
When a radio-collared moose dies, IF&W biologists conduct a necropsy in the field. They bring back samples, including the lungs and brain, which Lichtenwalner and her students test for diseases and parasites. Many of the moose samples the lab has analyzed have been infected with winter ticks, lungworms and lung cysts.
In late March and early April, the biologists usually see a surge in deaths.
“This is when the winter ticks are taking their biggest blood meal. The weather is changing, and the moose have used up a lot of their metabolic stores for the winter, and we’re a little early for new growth they may be browsing on. That’s when we tend to lose moose,” says Lichtenwalner, who affectionately refers to the animals as “charismatic megafauna.”
A single moose can carry tens of thousands of winter ticks. University of New Hampshire researchers estimated one moose in the study carried more than 60,000, with the average being around 47,000, Kantar says. A mature winter tick can expand to the size of a grape and fill itself with up to four milliliters of blood, according to the researchers.
An infested moose can become anemic, and essentially be drained of its blood. Calves are more likely to die because their smaller bodies are sometimes unable to handle the blood loss. Other animals, such as deer, have the ability to groom ticks from their bodies.
“Moose tend to rely on rubbing, but the ticks oftentimes can survive the rubbing. (The moose) end up losing their hair, but not the ticks,” Lichtenwalner says. Infested adults are often referred to as “ghost moose” because of their patchy and pale appearance caused by their attempts to rid themselves of the pests.
The IF&W study began in western Maine in 2014. That year, 73 percent of the collared calves died, followed by 60 percent the next year. In 2016, 26 of 35 collared calves in the western Maine study area did not survive, as well as 17 of 36 in the newly added northern Maine area, Kantar says.
Lichtenwalner says the data from the IF&W study can be used to help predict moose populations and inform decisions related to forest management and hunting permits.
The number of moose permits issued in Maine fell from 4,110 in 2013 to 2,140 last year — largely because of concerns about survival rates due to winter tick infestation. State wildlife biologists are proposing to reduce moose permits to 2,080 for the 2017 season to meet population goals, Kantar says.
Researchers believe tick survival may be increased by warming temperatures and shorter winters. In the fall, ticks wait in vegetation to attach themselves to passing animals. The later winter starts, the more time the ticks have to find an animal to grab onto to escape the cold and snowy weather.
“What we’re experiencing in Maine now is compression of winter,” says Susan Elias, a doctoral student in the Climate Change Institute. “It’s become a shorter season, so that means adult deer ticks can quest longer into the late fall and start earlier in the spring. That improves their probability of finding a blood meal, and once that female deer tick is fed, then she can overwinter and lay eggs in the spring.”
One adult female deer tick lays between 1,000 and 2,000 eggs, which will result in larvae the following August, according to Elias, who is researching the factors that affect the spread of deer ticks in Maine, as well as the diseases they carry.
Elias has a master’s degree in wildlife science and is a research associate at the Maine Medical Center Research Institute’s Vector-borne Disease Lab (VBDL). She also is part of the Adaptation to Abrupt Climate Change (A2C2) Integrated Graduate Education and Research Traineeship (IGERT) at the Climate Change Institute. The program provides funding to Ph.D. students for interdisciplinary research projects aimed at improving climate change adaption strategies.
In collaboration with the CCI, Elias says the VBDL predicts climate change will increase the risk of vector-borne illness to humans in Maine. Tentative conclusions are that milder winters and adequate moisture in summers, as well as higher daily temperatures, will allow the deer tick to complete its life cycle statewide, according to Elias.
In addition to climate change, Elias is looking into other variables that are thought to affect the spread of deer ticks.
“Certainly one driver is climate. That’s one piece of the puzzle, but it’s not the whole puzzle,” she says, citing other factors, such as deer and small mammal host density, and changes to tick habitat, including land use and invasive plants.
With help from other UMaine climate scientists, Elias is creating models that better integrate the variables by using existing data sets and software that simultaneously take into account several factors and indicate the relative importance of each.
In 2016, Elias conducted a survey of Maine’s island residents to better understand the attitudes and beliefs people have toward ticks, as well as what they’re doing to protect themselves.
“We’re seeing fairly high tick densities out on the islands and fairly high infections. There seems to be a high entomological risk out on these islands,” says Elias, who cites high deer densities and invasive plants, such as Japanese barberry and oriental bittersweet, as possible reasons for the increased risk.
The main reproductive host for the deer tick is the white-tailed deer. Some small island communities that don’t have a history of a regular firearm season have an overabundance of the animal, Elias says.
Thirteen of Maine’s 15 unbridged islands with year-round residents have deer herds that carry ticks. Matinicus never had a deer population, and Monhegan eliminated its herd in the 1990s after contacting the VBDL about its increasing number of Lyme disease cases.
Elias says the lab continues to be contacted by island residents who are concerned about the prevalence of ticks and Lyme disease. She says she hopes the survey can be the first step in developing a response to the increasing problem.
“Our approach to finding out what people are thinking and feeling is to better understand the community and, upon invitation, go in and consult and then help streamline this quasi-political process to try to grapple with tick control,” she says.
Tick management works best as a community effort, Elias says. In communities that are split on how to handle deer overabundance, she recommends tick control committees look into ways to tackle a less polarizing issue, such as eliminating invasive plant species, which can create a dense microhabitat and protective environment for ticks.
Elias says understanding the spread of Lyme disease is important because it speaks to the larger issue of the eco-epidemiology of infectious disease.
“Tick-borne disease is just one; other diseases could spread northward and we need to be prepared,” she says. “We need to be thinking ahead when we’re managing our yards, our communities, our state. We need to be thinking about how to reduce our risk of infectious disease.”
Allison Gardner, an assistant professor of arthropod vector biology in the School of Biology and Ecology, also is looking into the ecological processes that facilitate the expansion of vector-borne diseases.
The three tick-borne diseases in Maine that are currently undergoing substantial geographic range expansions — Lyme disease, anaplasmosis and babesiosis — are spreading at different rates and spatial patterns, Gardner says.
“Lyme has spread the farthest north and the fastest at this point,” she says. “Babesiosis is the most geographically confined; currently substantial human cases only are being seen in the southern part of the state.”
Gardner’s research will look at whether land use and/or climate change is responsible for the emergence and distribution of tick-borne disease in Maine.
All land use changes — increased residential development, forestry practices and terrestrial plant invasions — result in reduced complexity of habitat, Gardner says. As habitats become more simplified, many large mammals leave. These animals include predators of mice — the primary reservoir hosts of Lyme disease.
In the case of climate change, Gardner says one possibility for the spread of Lyme disease is that the deer tick has been transported north by animals capable of moving long distances, such as birds or deer. However, they haven’t been able to survive the winter to form a reproductive population until now.
Trying to assess the relationship between climate change and vector-borne disease is a complex problem, according to Gardner and Elias, because of the many components to transmission, including the vector, pathogen and hosts.
“The Lyme disease ecological model is one of the most complex models of disease out there,” Elias says. “Working out this puzzle is fascinating. You can’t do it alone. We need people from so many disciplines to get this figured out.”
Before coming to UMaine in 2016, Gardner’s research primarily focused on diseases transmitted by mosquitoes. Now her focus has shifted to tick-borne disease because it is of more concern in the region.
Gardner says the primary defense Maine residents have against tick-borne disease is awareness.
“People need to take steps to protect themselves by wearing appropriate clothing and being aware of times of year that are particularly high risk for tick-borne disease,” she says, adding adult ticks are most likely to be out in the spring and early fall.
The most important personal protection technique, according to Elias, is the tick check.
Also essential, Gardner says, is being better informed to make land use decisions that can either drive or inhibit the transmission of vector-borne disease.
Dill, who runs UMaine Extension’s tick identification program, is pursuing a Ph.D. in ecology and environmental sciences. His research also is concentrated in the ecology of ticks, specifically in relationship to their hosts.
In summer 2016, he conducted a pilot project at farms around the state. At each location, he live-trapped small mammals, pulled off any ticks and took an ear snip to test for tick-borne disease. While his initial study looked at farms and potential risks for workers, Dill plans to expand his research to look into the relationships among tick densities, habitats and small mammal hosts. He is in the process of analyzing the data and plans to dive deeper into the research once the new Plant, Animal and Insect Laboratory opens.
“There’s a lot of fear and disinformation related to ticks out there, so it’s incredibly important to have a facility like this where we can conduct research, but also (operate) as a hub for disseminating information directly to the public,” Dill says.