Tick Talk
The inaugural director of the Lyme and Tickborne Diseases Institute tackles the growing threat of tickborne illnesses.
In January 2021, the CDC offered a stunning revision of the scale of Lyme disease in the U.S. Using insurance data, it estimated annual cases at 476,000—nearly 14 times higher than previous counts reported to the CDC by health departments.
“I think there’s still not an awareness of how many people get infected every year. We need a comprehensive approach to protect the human population, not just from Lyme, but from tickborne diseases in general,” says Nicole Baumgarth, DVM, PhD, who has studied tickborne illnesses for more than 20 years. She joined the Bloomberg School in July as the inaugural director of the Johns Hopkins Lyme and Tickborne Diseases Research and Education Institute.
Previously at the University of California, Davis, Baumgarth has made key discoveries on how the Lyme bacterium—transmitted to humans through the bite of black-legged ticks—disrupts the immune system.
For years, there has been debate about whether chronic or persistent Lyme disease exists. What’s your take?
[The medical establishment has] basically said to patients, “If you have been treated with antibiotics, you’re fine.” But when patients come back and say, “I’m not feeling fine,” they were often told “it’s all in your head.”
[They] were saying the same things to people with long COVID. But having 96 million cases [of COVID-19] in the U.S. alone is a different thing. If even 0.1% of people develop ongoing symptoms, you have a huge population of patients and you can’t ignore them.
With long COVID, we have a concept that didn’t really exist before. You say “long COVID” and [people] know exactly what it means: You had the infection. You cleared the virus in all likelihood, but you’re still feeling ill for weeks and months later.
I think now the idea is not so alien anymore.
The spirochete Borrelia burgdorferi causes Lyme disease and has quite a unique lifecycle.
This spirochete establishes persistent, ongoing infection in a number of different species that ticks can bite, including mammals, birds, and reptiles. The ticks need a new host at each stage of life [larva, nymph, and adult] to survive, and this lifecycle lasts about two years. What’s really important to understand is that adult ticks cannot pass on B. burgdorferi to their eggs. Because there is no permanent infection cycle maintained in ticks, the best way that B. burgdorferi can maintain itself is to ensure that tick larvae have access to populations of species that are continuously infected.
How did this lifecycle influence your research?
Once I understood that, I realized that when humans get infected, the spirochete is trying to establish ongoing infection, like it does in these “natural reservoirs.” And for that, it needs to do something to subvert the immune response—suppress it, alter it—in order to survive inside the host.
In the end, we need to develop a vaccine. Climate change is causing the ticks that can be infected with Borrelia to spread further and further.
Some of your work in mouse models has overturned assumptions about Borrelia’s impact on the immune system.
The thinking was that B. burgdorferi hides and doesn’t do much—it just crawls into tissues and sits there. We showed that is completely wrong.
After you infect a mouse with B. burgdorferi, within 24 hours you can find it in a lymph node, which is the hub where all the immune cells come together to start an immune response. So instead of hiding, it’s waving a red flag, alerting the immune system to its presence. The outcome is that an immune response is induced that is not effective at clearing the infection but controls the infection sufficiently so that mice do not get sick.
We also found that when you give B. burgdorferi-infected mice a flu shot they will make fewer antibodies in response. My lab has been working on trying to understand exactly how Borrelia interferes with the immune system to achieve this.
What are you excited about in Lyme disease research?
One of the biggest problems with treating Lyme disease in humans is that the best way we know right now is with a very broad-spectrum antibiotic. Antibiotics have side effects. One of them is that they wipe out your gut microbiota, [which] is really important for maintaining health. A study by Kim Lewis [at Northeastern University] has identified an antibiotic that seems to very specifically attack only spirochetes. If it turns out to be effective in treating human patients, I think we’ll learn a lot.
In the end, we need to develop a vaccine. We’re not going to stop going into forested areas. Climate change is causing the ticks that can be infected with Borrelia to spread further and further. And there are some interesting developments in finding good antigens on the pathogen to see what we can target to make the best vaccine. There’s also work on using mRNA vaccines that target tick salivary proteins and trigger an immune response that inhibits the tick from establishing good feeding and might prevent transmission of this infection and others carried by ticks.
What is your vision for the Center’s first few years?
I like the idea of focusing on work that can complement and enhance the work at the medical school’s Lyme Disease Research Center, directed by John Aucott, so that we can make the sum of our collective work bigger than its parts. That involves developing a better understanding of the pathogenesis of tick infections, looking at the immune response, and looking at the pathogens. I would really love to recruit a couple of people that can strengthen the understanding of the bugs and somebody working on the tick so we have the different pieces in place and can develop a bigger program.
Because this is a school of public health, we want to be focusing on the aspects that we need to understand to be able to help with policies. How do we tackle increasing populations of infected ticks? How can we identify strategies to develop diagnostics and vaccines? Because we are a center of learning, we want to try to recruit the brightest trainees and begin to train cohorts of people that are committed to future research in tickborne diseases.