The engineered rodents would look exactly like the native white-footed mice. But each of their cells would carry genetic code, specially tailored in an MIT lab, for resistance to the bacteria that causes Lyme disease. White-footed mice are a key reservoir for the harmful bacteria.
Because mice breed so quickly and prolifically, the scientists are betting the genes of the new rodents would predominate soon after their release. The immunized mice, they hope, would curb the spread of Lyme, which has increased dramatically here in recent years and is now the most common infectious disease on the island.
If fewer mice carry Lyme, the scientists say, fewer ticks that bite them would become infected. That, in turn, would mean fewer ticks that bite humans would carry Lyme, which is becoming more prevalent throughout New England as a warming climate allows more ticks to survive winter.
“With so many people suffering from Lyme every single day, which is an awful disease, we need a solution urgently,” said Joanna Buchthal, research director of the MIT Media Lab’s Mice Against Ticks project, who has close friends who suffer from Lyme and other tick-borne diseases. “This offers a real, if revolutionary, way to tackle the problem.”
But some fear that tinkering with nature by using new gene-editing technology could lead to a host of unintended consequences, which the scientists acknowledge are legitimate concerns.
“Technology can make the world worse,” said Kevin Esvelt, a biologist and associate professor at MIT who helped found the project. “Our overall goal is to advance this safely, safeguarding it from mistrust and misuse, and setting a precedent for how this is done.”
Their first-of-its-kind proposal would require significant vetting by local, state, and federal regulators, such as the Food and Drug Administration. It will also require support from residents here and on Martha’s Vineyard, where the scientists also hope to release hundreds of thousands of engineered mice.
Getting that support remains far from certain, given deep-seated concerns about genetically modified organisms.
As part of that effort, the scientists this month held a public meeting on Nantucket to explain their plans and seek feedback.
Addressing scores of residents gathered at a restaurant in the historic district, Esvelt began with a promise that the project would only proceed if residents approve it. “If at any time the community says nope, we’re not interested,” he said, “then we walk away.”
The team’s larger goal, he said, is to demonstrate how to go about such controversial experiments with as much transparency and community guidance as possible.
“We can do things that were unimaginable just a decade ago,” Esvelt said. “But if we invent a technology that changes the environment, then even if it comes up for a community vote, and you vote against it and the rest of the community votes for it, you’re going to be affected no matter what.”
Given the potential consequences to the ecosystem from such genetic modifications, the team plans to make the fewest possible changes to the mice to minimize any unintended consequences, Buchtal said.
Rather than transplanting specially designed genetic code in the white-footed mice, which would be more efficient, they plan to insert specific Lyme-resistance genes from white-footed mice that have developed immunity to the disease through exposure to it.
White-footed mice that acquire Lyme immunity can’t pass it on to their descendants. But gene editing can make that immunity inheritable. So the altered mice, if all goes well, would pass that immunity to their descendants, eventually replacing all the mice susceptible to the pathogen.
The team, which has raised millions of dollars from federal grants and private philanthropists, has proven that they can insert that acquired immunity gene into the genes of laboratory mice, and that those altered mice are resistant to Lyme, a first step toward immunizing white-footed mice, Buchthal said.
Before releasing the mice into the wild, the team plans to conduct field trials on several small, largely uninhabited private islands in the region. (They won’t disclose the location until the property owners have confirmed their participation, they said.) They also plan to bring in independent ecologists to monitor the experiments for any red flags.
“That’s why it’s especially important that we go slow; we involve regulators; we include more voices; and we ask for as much scrutiny as we could possibly have,” Buchthal said.
Those promises, however, didn’t fully reassure some of those who attended their presentation.
Among the concerns about unintended consequences: If Lyme disease is no longer prevalent, would that allow for a surge in other invasive species? Could the population of mice and other rodents also grow significantly, or exhibit new traits, such as becoming more aggressive, and if so, what might be the consequences of that? Could there be harmful ramifications for other species that consume the mice?
More urgently, perhaps, they wondered how such an experiment could be regulated effectively, and what could be done to halt any negative consequences once the mice spread in large numbers. Moreover, while the team would be able to track changes in the prevalence of Lyme disease, it was unclear whether it would even be possible to link the genetically modified mice to, say, a decline in the owl population.
“This is scary technology,” said Allison Snow, an ecologist at the University of Massachusetts Amherst who studies ticks and also attended the meeting. “There’s still so much they don’t know.”
Yet most of those who listened to the scientists, including Snow, said they’re keeping an open mind.
Max Wolf, an Episcopal priest on the island, had figured it would never survive a vote at Town Meeting.
“I expected there would be a lot of vocal opposition at the meeting,” he said. “Instead, I sensed great relief. I’m surprised and hopeful at the positive reaction.”
The receptivity to their pitch comes, in part, to the increasing prevalence of Lyme disease on the island. Lyme can cause arthritis, an irregular heartbeat, inflammation of the brain and spinal cord, and problems with short-term memory. In rare cases, it can be fatal.
Last year, health officials on the island recorded 169 cases of Lyme, nearly three times the number of infections five years before. In that time, there were also scores of cases of the other tick-borne diseases, babesiosis, a parasitic infection of the red blood cells, and anaplasmosis, a bacterial disease. Both can cause flulike symptoms and, though treatable, can in some cases be life-threatening.
Between 2009 and 2018, tick-borne illnesses accounted for more than 90 percent of all infectious diseases diagnosed on the island, according to a study by the Nantucket Health & Human Services Department.
“There’s a plague of Lyme disease on the island, and that’s why I support this proposal,” said Roberto J. Santamaría, director of the Nantucket Health & Human Services Department. “Lyme has reached a critical point, and the worst thing we can do is nothing.”
He worried it would get worse as climate change accelerates. “The warmer it gets, the more active the ticks are, and the more people they bite,” he said.
The longest-serving physician on the island, Dr. Tim Lepore, also endorsed the proposal. Previous efforts to try to reduce Lyme by culling the island’s population of roughly 2,500 deer haven’t been successful.
“People didn’t like seeing a lot of deer shot, and I don’t think we’re going to see people flying in helicopters over the island firing M16s,” he said. “So I think this is going to be an important part of our armament to deal with this.”
The main concern of many proponents was that the project would take too long or never make it through the regulatory process, as there’s little precedent for state and federal officials in approving the introduction of such genetically modified species into the wild.
The only similarly scaled experiment, which took about a decade to win regulatory approval, was when a United Kingdom-based firm last year released genetically engineered mosquitoes in the Florida Keys, with the goal of reducing the spread of diseases such as dengue, Zika, and chikungunya.
At the meeting, another member of the team of scientists, Sam Telford III, a professor of infectious diseases and global health at Tufts University, acknowledged that they still had much to learn and that there remain many reasonable questions.
Answering them will be difficult, and it will likely be years before any altered mice are released onto the island, he said.
But if the experiments prove successful, Telford added, it’s likely they would eventually be introduced on the mainland.
“We’re not saying Mice Against Ticks is the magic bullet,” he said. “It’s one of many options. We want to give communities as many potential ways to deal with the problem as possible.”
As the meeting ended, Telford and the team distributed pairs of white tube socks treated with a special insecticide to protect residents.
“As of now, this is the best option we have,” Buchthal said.