Ticks Pose an Increasing Health Risk
With no vaccines yet and limited treatment options, avoiding tick bites is our best bet in reducing the risk of tickborne illnesses.
The vast majority of vector-borne diseases in the U.S. are caused by ticks and the viruses, bacteria, and parasites they carry.
Between 2019-2022, all 50 states and Washington, D.C. reported cases of tickborne diseases. Lyme disease is the most common, but there are a dozen or so lesser-known tickborne illnesses that are on the rise. In an April 28 episode of Public Health On Call, Nicole Baumgarth, DVM, PhD, spoke with Stephanie Desmon all about ticks and the diseases they can cause, progress towards vaccines, and how climate change is increasing where and when ticks can thrive.
Baumgarth, a professor in Molecular Microbiology and Immunology and director of the Lyme and Tickborne Diseases Research and Education Institute, explains that because we don’t yet have vaccines and treatment options are limited, awareness and individual prevention strategies remain our greatest assets for reducing risks of tickborne illnesses.
How prevalent are ticks in the U.S.?
Ticks are unfortunately common in the U.S. and becoming even more common. There are about 15 states in which ticks are considered endemic, primarily in the Northeast—Connecticut, New York, and Maryland—as well as California.
Ticks carry viruses, bacteria, and parasites that can cause all sorts of diseases in humans.
How prevalent are tickborne diseases?
Many people are surprised to hear that in the U.S., 90% of all diseases caused by getting bitten by something—including mosquitoes—are actually caused by ticks. Lyme disease is by far the most common vector-borne disease in the U.S.
We don’t know exactly how many people develop Lyme disease every year, but based on the best evidence we have, the CDC has recorded about 475,000 cases a year—that’s an incredibly high number.
How can we protect ourselves from tickborne diseases?
If you’re spending time in the woods in a region where ticks are common, effective tick prevention involves looking a little bit dorky: You should wear long sleeves and long pants, with the pant legs tucked into your socks. And if you want to look even more dorky, wear a hat. Essentially, you want to minimize any exposed skin where ticks can bite you.
After your walk or hike, it’s important to also check yourself for ticks and pull off any you find. You can also take a hot shower and change into fresh clothing.
Currently, prevention strategies like these are all we have. There are no vaccines for any of the diseases that are carried by ticks.
What are the symptoms of Lyme disease?
Lyme disease causes nonspecific flu-like symptoms, which can make it harder to diagnose quickly in people who don’t know that they’ve been bitten by a tick or don’t have the bullseye rash around the site of the bite. Doctors may be more likely to consider Lyme disease as the cause in states where ticks and Lyme disease are common. If you experience flu-like symptoms after traveling to a place where ticks are common, tell your doctor, as this may help inform the diagnosis and treatment.
If Lyme disease is diagnosed rapidly, a person can be treated with antibiotics and most people will fully recover. However, about 10% or so who get infected will have ongoing symptoms. And that’s still a really high number—that’s about 45,000 individuals per year who will have ongoing Lyme disease symptoms.
Why are cases of Lyme and other tickborne diseases increasing?
There are multiple reasons behind the increased risk of tickborne diseases in North America. With a warming climate, ticks are actually moving farther north. There were no cases of Lyme disease in Canada even 20–30 years ago, and now Lyme-carrying blacklegged ticks are present in the southern parts of Canada. Ticks didn’t used to be able to overwinter, but now they can.
Human behavior also plays a role: Humans like to live where ticks like to live—at the edges of the woods. As we’ve moved out into the countryside and areas that are perfect habitat for ticks, that also increases our risk of being exposed to ticks.
We’re also seeing populations of certain species of ticks spread to new regions. For example, the lone star tick (Amblyomma americanum), which used to only be found in the South, is now the most common tick found in Maryland.
Does the lone star tick carry the same illnesses as blacklegged ticks?
The lone star tick does not carry Lyme disease, but it carries some others. The most common complications caused by lone star ticks are STARI (Southern Tick-Associated Rash Illness) and alpha-gal syndrome, a red meat allergy that can be life-threatening.
Alpha-gal syndrome is caused by a sugar molecule—called alpha-gal—that is present in the saliva of the tick and in red meat. Humans can’t make this sugar, and if you’re exposed to it from a tick bite, you can become allergic to red meat and other products from mammals.
What other tickborne illnesses is your Center investigating?
Lyme disease is caused by a bacterium, but ticks can also transmit viruses, including Powassan virus and Heartland virus. Currently, there are no treatments for these viruses which can cause severe disease, including meningitis, encephalitis, and even death [in some cases]. Because there is no cure for these, you can treat the individual symptoms, but not the infection itself.
What is babesiosis?
Babesiosis is another disease that seems to be becoming more common. It is a little parasite that lives inside red blood cells. Among tickborne diseases, babesiosis is one of the easier ones to diagnose, because the parasites can be identified quite easily in blood cells.
Babesiosis is particularly concerning because it can be transferred through the blood. We now test donated blood for the Babesia parasite, because the blood supply is often given to people who have an existing illness or whose immune systems are already compromised.
It’s also possible for a pregnant woman infected with Babesia to transfer the infection to her baby at birth, even if she does not have symptoms. Because the baby is not immunocompetent, they can get very sick.
Are there vaccines in development against tickborne diseases?
A Lyme disease vaccine is currently in Phase 3 clinical trials that are testing for efficacy, or how well it actually protects a person from Lyme disease.
This is a vaccine against the bacterium that causes Lyme disease—not as it is in our bodies, but as it is in the tick. The idea is that the vaccine would cause you to make antibodies to the antigen that is expressed by the bacterium in the tick. A tick would then pick up the antibodies when it bites you, preventing it from ever infecting you.
One new idea that I’m very excited about is: Can we develop a vaccine against tick bites and ticks in general? The idea is that the moment a tick starts biting you, you’d develop an immune response and expel the tick from the skin. If that could work, it wouldn’t matter what pathogen they carry—we would not actually get infected. We’re years away from that, but there is basic research going on now trying to figure out how to do this.
Has work on tickborne illnesses been impacted by funding cuts?
Yes, unfortunately it has been. There have been cuts to earmarked funding to support tickborne disease research, mainly around Lyme disease. This includes medical research supported by the Department of Defense, which has a particular interest in protecting soldiers and their families from illnesses.
There was also a public-private partnership called Lyme-X between the Steven & Alexandra Cohen Foundation and the NIH aimed at developing better diagnostics. The office that gave out the public part of that partnership was cut.
It is a tricky time, not just as a tick researcher, just as a researcher in general. It’s hard to know what the priorities are. The research we do takes decades. I've been working on tickborne diseases for 20 years, and research is incredibly slow and painstaking. It’s always great to talk about breakthroughs, but it's a bit of a misnomer—it’s more like crawling through than breaking through.
I started working on Lyme disease because I was interested in the immunology underlying the disease. There are so many people affected but so few resources. We want to make progress, so we really need to keep the research going. We cannot allow it to stop, even for a few years.
This article was edited for length and clarity by Aliza Rosen.
