Fighting the spread of Lyme disease
NSF-funded research on Lyme disease has sparked groundbreaking discoveries helping Americans stay safe and healthy
Lyme disease is emerging as one of the fastest-growing threats to human health globally. In the U.S. alone, over 89,000 cases were reported by state health departments and the District of Columbia as part of regular surveillance in 2023.
Research supported by the U.S. National Science Foundation is improving understanding of Lyme disease, how it is transmitted and how to limit its spread.
What is Lyme disease?
Lyme disease is a bacterial infection spread primarily by the bites of deer ticks (also known as black-legged ticks). Early symptoms of the disease resemble the flu — fever, chills and muscle aches — often coupled with a large rash.
The Centers for Disease Control estimates Lyme disease costs the U.S. between $345 million and $968 million annually, with costs averaging about $1,200 per patient for early treatment and doubling for late-stage cases of the disease.
Don't just blame the ticks
Ticks aren't born carrying Lyme disease. Instead, they pick up the bacteria that cause the disease when feeding from infected animals and can later pass it on to humans through their bites.
While deer ticks get their name from their habit of feeding on deer (a single deer can have over 1,000 ticks on its body), deer aren't a prime factor in the spread of Lyme disease. That's because the immune system of deer can quickly flush out the infection before it can get picked up by ticks and transmitted to other animals.
In 2014, research supported by NSF and the National Institutes of Health found that small mammals like mice, chipmunks and shrews play a major role in transmitting Lyme and other diseases to ticks.
This finding suggests that coyotes and foxes, animals not often associated with Lyme disease, may have a big role to play in the disease's spread. When these predators aren't present, small mammal populations can increase, which, in turn, leads to an increase in the number of ticks. The NSF National Ecological Observatory Network is tracking the populations of small mammals at field sites across the country, contributing vital data on where these animals are migrating and how other changes in the ecosystem can affect their populations.
At the other end of the food web, researchers have examined the role that oak trees, which provide food for chipmunks and mice, play in the spread of Lyme disease. They found that the strongest predictors of Lyme disease risk in a given year are the number of mice and chipmunks the year before and the abundance of acorns two years before.
Birds, often overlooked in Lyme disease spread, can carry infected ticks across great distances. In 2021, NSF-funded disease ecologists at the Cary Institute of Ecosystem Studies used machine learning to identify bird species most likely to transmit ticks with the Lyme disease-causing bacteria. Their model highlighted 21 species, including American robins and true thrushes, to target with surveillance.
Understanding how these organisms contribute to the disease's spread is key to finding strategies to prevent and control Lyme disease infections.
Understanding the root cause
Why does Lyme disease spread as well as it does? NSF-supported researchers at Woods Hole Oceanographic Institution have been investigating the bacterial pathogen behind the disease to understand how it evades host immune systems. The researchers, along with those from Johns Hopkins University and The University of Texas, found that the Lyme disease-causing bacteria, B. burgdorferi, can survive without iron.
Most organisms need iron to produce proteins and enzymes, but B. burgdorferi relies on manganese instead, using it to produce an enzyme critical for its survival. This adaptation allows the bacterium to escape immune system defenses that cut off the flow of iron to the gut and bloodstream in an attempt to starve invading pathogens of the critical metal.
Understanding this unique trait, along with information on how the bacterium avoids other immune responses, can help lead to new treatments.
Slowing the spread with citizen science
With no preventive medicine for Lyme disease, avoiding ticks is the best defense. But ticks thrive in places where Americans like to live and play — warm, wooded areas, tall grass and at the edges where natural landscapes meet lawns and parks — increasing people's risk of exposure.
In 2019, an NSF-funded research team studied how ticks invade human-dominated spaces like backyards and city parks. Starting in New York, the project later expanded to Michigan, Illinois and Wisconsin, all parts of the U.S. where Lyme disease is especially prevalent.
Using lessons from their research, the team released The Tick App, a free smartphone app that allows users to see where ticks have been reported in their community, report tick sightings and learn how to identify ticks and protect themselves.
The information people share in the app helps improve research on Lyme disease, too: by combining all this information into computer models, The Tick App team has identified which combinations of urban green space sizes and connectivity help ticks survive and which ones make survival less likely.
Trekking forward
While Lyme disease is the most common tick-borne illness in the U.S., it's not the only one on the rise. Other rapidly increasing diseases include those caused by bacteria like Rocky Mountain Spotted Fever and anaplasmosis, and babesiosis, which is caused by a malaria-like parasite.
NSF is actively exploring new tools and technologies like machine learning, modeling, citizen science and biological monitoring to better understand and combat the threats of Lyme disease and other tick-borne ailments, both to public health and the economy.