Genetically engineered mice could take the bite out of Lyme disease on Nantucket, scientists say

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Genetically engineered mice could take the bite out of Lyme disease on Nantucket, scientists say

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Jon LaPook, Denise Schrier Cetta, Aliza Chasan, Katie Brennan,  CBS News,  2025.

Over the past 40 years, Dr. Timothy Lepore has been the emergency room head, sole surgeon and medical examiner on Nantucket, a small island off Cape Cod, Massachusetts. Today he runs the only private practice, where he treats dozens of patients with Lyme disease each year. About 15% of residents on the island have been afflicted with the disease, which can cause a wide range of symptoms like a fever, rash, facial paralysis, an irregular heartbeat and arthritis. Lepore, 80, may finally be able to retire if a team of scientists’ dream to curb the transmission of Lyme disease on the island becomes a reality. The scientists’ target is not the deer or ticks often associated with the disease: it’s wild mice, the main host of Lyme bacteria. The hope is that by genetically engineering mice to be immune to Lyme and releasing them in Nantucket, the population of mice able to spread Lyme disease on the island will shrink.

The problem on Nantucket can be traced back to 1926, when the community voted to import two female deer to the island to give a lone buck company. On top of that, by the 1950s, half the land on the island was put into conservation. The untamed brush and wild grasslands create an ideal ecosystem for Lyme’s hosts to thrive. As the deer population grew, so did the population of ticks. Deer don’t get Lyme, but female ticks feed on them, and then lay as many as 2,000 eggs in a single batch. Deer also spread the disease as thousands of them carry ticks across Nantucket. Not all ticks carry Lyme disease, and a tick bite doesn’t guarantee the transmission. Even if the tick is carrying Lyme, the tick has to be attached for more than 24 hours to infect someone.

While most people associate Lyme disease with deer and ticks, white-footed mice are the main host of Lyme bacteria. When an uninfected tick bites an infected mouse, the bacteria transfer to the tick. When an infected tick then bites an uninfected mouse, the cycle continues. “We have a problem with tick-borne disease because we engineered the environment to maximize the number of ticks and maximize the number of mice that are the best hosts of Lyme disease,” Kevin Esvelt, a genetic engineering pioneer and associate professor at MIT, said. “It came back and bit us, literally.” Lyme disease can be treated with antibiotics, but if left untreated, the infection can spread to the heart, joints and nervous system, as it did for 33-year-old Shauna Asplint, who was first diagnosed with Lyme when she was 10. A few years later, the left side of her face stopped moving, a residual effect from the disease still noticeable today. Lyme disease afflicts nearly half a million people a year in the United States, according to the Centers for Disease Control and Prevention. The disease is rarely fatal.