Could Fire Be the Solution to the East Coast’s Tick Woes?
How researchers hope to use an old technology to stop the spread of tick-borne diseases
In March of 2023, the Centers for Disease Control and Prevention reported that cases of babesiosis, a parasitic infection similar to malaria, have “increased significantly” in no less than eight Northeast states. Babesiosis, like Lyme disease, is transmitted by ticks and is now endemic throughout much of the East Coast, according to the CDC. Notably, states with entrenched babesiosis now include Maine, Vermont, and New Hampshire, places where it had previously failed to create a stronghold.
Lyme disease and babesiosis are not the only pathogens transmitted by ticks. North American tick species carry multiple illness-causing bacteria, parasites, and viruses. In fact, 77 percent of vector-borne diseases in the US are spread by ticks, according to the CDC. To many, it’s clear: To stop tick-borne diseases, we need to stop the ticks.
Yet, to date, no single tick-control method has been widely adopted by government agencies. But that could change if leaders get over their fear of fire. A small group of pioneering researchers are studying how controlled (prescribed) burns could be used to slow the spread of ticks and their pathogens. Their results are promising and follow on the heels of decades of failed attempts to use fire as a control method. Fueling this new success, say these researchers, is a recent shift to a more holistic ecological perspective on the epidemiological problem of tick-borne illnesses. According to some, long-standing fire suppression policies held by state and federal agencies are one reason for the rise in tick-borne illnesses.
This is the major idea behind a 2022 paper published in the journal Ecological Applications. The paper not only argues that prescribed burns could help control the spread of tick-borne pathogens in the eastern US, but it also contends that fire suppression has helped tick habitat expand in the region, spreading illnesses as a result.
“[Fire suppression] is not the only factor, but it’s one of the factors and one that has been overlooked,” says study lead author Michael Gallagher, research ecologist at the US Forest Service Silas Little Experimental Forest near New Lisbon, New Jersey.
Fire suppression now joins a long list of ecological disruptions linked to the rise in tick-borne illnesses, including warming temperatures tied to climate change. Other ecological disruptions noted in Gallagher’s paper include larger populations of deer, which ticks both feed and breed on. Deer populations on the East Coast have exploded due to the near extermination of predators. And they have also benefited from the natural regrowth of forests that followed the decline of local farming. This, coupled with an increase in the number of people moving into tick-endemic areas in the urban-wildland interface, has led to more ticks and more people exposed to them and the pathogens they carry.
Reintroducing fire in this context could reduce tick populations and restore ecosystems, according to Gallagher. His argument is simple: Ticks need moist environments to survive. This is especially true for Ixodes scapularis—the deer tick or black-legged tick—the carrier of the pathogens behind Lyme disease and babesiosis.
Ideal conditions for these ticks are created by closed-canopy forests that keep sunlight out and moisture in. Exactly the type of forest that has regrown in large sections of the eastern US since the widespread policy of fire suppression. What ticks don’t tolerate well are drier, hotter, fire-adapted landscapes with open canopies that allow sunlight to penetrate to their lower levels.
This insight, however, doesn’t originate with Gallagher. It appears to be the brainchild of Elizabeth Gleim (a.k.a. “Tick Lady”), associate professor of biology and environmental studies at Hollins University in Roanoke, Virginia, who has authored three studies examining the long-term effects of fire on tick populations.
“There’s no question fire is going to kill a large percentage of ticks,” says Gleim. “But whether those reductions are going to be sustained really has more to do with the forest structure and whether you have a closed canopy or not.”
Over the past decade, Gleim’s research in the diverse, fire-adapted, longleaf pine ecosystem of southwestern Georgia and northwestern Florida has provided the ecological framework for understanding how fire, ticks, and forest structure interact.
In a 2014 paper published in the journal PLOS One, Gleim and colleagues were the first to demonstrate that prescribed burning could significantly lower tick populations. While previous studies had shown that tick numbers dropped immediately after a burn, they tended to rise again within a year following burning. Gleim was able to show that, if done over a long enough period of time and over a large enough area, prescribed burning could keep tick numbers low for years.
An even more promising breakthrough followed in 2019. The research, published in Nature Scientific Reports, demonstrated that not only could prescribed burning reduce the number of ticks, it could also reduce the number of pathogens found in the ticks that survived post-burning, something no previous study had demonstrated. “Given the volumes of research on fire’s effect on ticks, I was kind of shocked to learn that very few people had really looked at whether fire had affected pathogens,” says Gleim.
But not everyone is convinced that fire is a realistic strategy to control tick-borne illness. “With all the things going with fires now, what’s happening in Hawai'i and people in the West seeing their homes go up in flames, the last thing I think people want to do is introduce fire to residential areas,” says Thomas Mather, director of the University of Rhode Island Center for Vector-Borne Diseases in Kingston, Rhode Island.
Mather says controlled burns just aren’t practical in the heavily populated eastern US, where people are most likely to contract a tick-borne illness in their own backyards. “I don’t know of anybody who is thinking about applying burns for the management of ticks,” says Mather.
In 1993, Mather published his own study on prescribed burns as a way to control Lyme disease. He found that while tick abundance dropped following burning, burning didn’t lower the likelihood of finding a tick infected with the pathogen behind Lyme disease. Interest in ticks and prescribed burns first captured the imagination of modern researchers in the late 1970s, following the emergence in Lyme, Connecticut, of a supposedly new illness of unknown origin that would later share the town’s name. When Lyme disease was linked to a tick-borne pathogen in the early 1980s, a flurry of new research emerged on how to control the spread of ticks, including with fire. But by the early 2000s, interest in using fire to stop tick-borne illness fizzled out.
However, the idea that fire could be used to control ticks goes back even further than the 1970s. Land managers in the Southeast, where prescribed burning is widespread, knew that fire could control tick populations in the earlier part of the 20th century. In his 2022 paper, Gallagher cites a 1955 journal article that mentions observations made in Delaware during the mid-1700s. Prior to colonialization, the area had been widely burned by local Indigenous peoples but suffered from an explosion of ticks following early fire suppression, according to observations recorded at the time.
Complicating the issue is the still largely under-studied history of burning by Indigenous peoples. Gleim says there is no evidence that the East Coast’s original inhabitants used fire to control ticks but says evidence suggests that prescribed burning was widespread prior to European settlement.
“We now know that a lot of those [historical] fires that we are seeing on those [long] time scales were probably being set by Indigenous people,” says Gleim. “And we know now that they had incredibly sophisticated management and that fire was used on a regular basis.”
As to why interest in fire to control ticks died out in the early 2000s, Gleim’s 2014 paper suggests “conflicting results” and an inability to account for the larger ecological implications of using prescribed burns were major factors. But while both Gleim and Gallagher are advocates for prescribed burning to control ticks, they are both keenly aware that it might not work everywhere.
Gallagher’s study, in particular, comes with a large caveat. The study notes that some sections of the East Coast—including areas where both Lyme and babesiosis are now endemic—are not good candidates for prescribed burning because, historically, fire was very rare in these naturally wet regions. However, the study also notes that the total area where prescribed burning could be used to both restore eastern US ecosystems and control ticks is huge and covers most of the land east of the Mississippi River.
“I don’t mean to suggest that there is a silver bullet to this or any other ecological problem,” says Gallagher. “Prescribed burning is already done for a lot of other management reasons, but there may also be benefits for restoring habitat with fire that reduces ticks in a holistic way.”