We Are Not Ready for Exploding Tick Populations

As tick ranges rapidly expand across the United States and Canada, experts caution that antibiotics alone will not be enough.

Bitten by two different deer ticks eleven years apart, Dr. Joe Gillespie is unlucky because the bacteria (Borrelia burgdorferi) that causes Lyme Disease rushed into his bloodstream both times. On each occasion, the classic bulls-eye rash of Lyme Disease appeared, a glaring-red signal that an infected tick had feasted upon him. But the second bite was different. Afterwards, he lost most of the hearing in one ear, and experienced a constant ringing, a condition called tinnitus. "When I lie down at night, I hear tinnitus. That's the last thing I hear. I hear it now," Joe says. He developed vertigo—dizzying episodes where he could barely stand or walk straight. For the first time in his life, he began having anxiety and panic attacks. As the years went by, it only got worse.

After Joe's doctors conducted many tests, they were still puzzled. They told him he had Meniere's disease, a rare condition that causes vertigo, hearing loss, and tinnitus. The symptoms sounded familiar, but when he read about peoples' experiences with Meniere's, it didn't sound like what he was physically feeling. It helps that Joe is a microbiologist who studies tick-borne illnesses at the University of Maryland School of Medicine. It took his collective knowledge and an open-minded head and neck surgeon, Dr. Bryan Ward, to realize the extent of the damage to his inner ear. Inflammation in this area releases the same chemicals that trigger panic attacks. The suspected cause? His past Lyme Disease infections.

Joe took a course of antibiotics after both rashes appeared, which is the current prevention strategy for Lyme Disease. However, according to the CDC, the tell-tale bulls-eye appears in only about 70 to 80 percent of people who’ve been bitten, and the remaining 20 to 30 percent may never seek care because they don’t even realize a tick has bitten them. Furthermore, while the preventative antibiotics reduce the risk of infection by about two-thirds, some people—like Joe—will still get Lyme Disease.

And people’s exposure to the disease-causing bites is only getting worse. In Canada, Lyme Disease cases have increased by more than 6-fold in ten years, from 2012 to 2022. And recent estimates by the CDC suggest that about 476,000 people may get Lyme Disease in the United States each year. “I used to be able to say, ‘Well, if you go to Maine, you won't get Lyme disease’,” says Dr. Douglas Norris, an arthropod-borne disease researcher and professor at Johns Hopkins Bloomberg School of Public Health. “And in the last couple of years, Maine has had the highest incidence of Lyme Disease per capita.”

Tick populations are ballooning due to a variety of factors including climate change, increasing deer populations, and changes in bird migration patterns. According to the National institutes of Health, the geographic range of deer ticks that carry the Borrelia burgdorferi bacteria that causes Lyme Disease is expanding as well. Data from the University of Guelph in Ontario suggests that ticks are colonizing eastern Ontario at a rate of 28 miles per year. As the geographic range of deer ticks continues to expand, we need a better strategy than relying on post-exposure antibiotics to control infections.

In response to a need for more medical interventions for Lyme Disease, a Yale University lab is developing an mRNA Lyme Disease vaccine called 19ISP. Dr. Sajid and her colleagues developed this vaccine to mimic “tick immunity”—a phenomenon observed in animals that are repeatedly exposed to ticks. It is thought that these animals develop resistance to the proteins in tick saliva. So, the researchers isolated 19 proteins present in tick saliva, and engineered the genetic instructions to create them—mRNA. This mRNA encoding the 19 tick salivary proteins was injected into test animals. The test animal’s own cellular machinery is then able to create the proteins and churn them out into the body. Since the tick salivary proteins are not naturally occurring, the test animal’s body recognizes them as foreign, and an immune response is triggered. When the animals reencounter these proteins—after an actual deer tick bite—the immune system rapidly starts fighting and forces the tick to let go.

The researchers tested 19ISP on guinea pigs at different time points, since ticks must attach to an animal for 36 to 48 hours before transmitting the bacteria that causes Lyme Disease. The immunized guinea pigs were all negative for Lyme Disease after being bitten by a single infected tick that fell off. However, over 60 percent of vaccinated and unvaccinated guinea pigs were positive for Lyme Disease when three disease-carrying ticks were allowed to attach to their bodies and fall off. The bright side is that all vaccinated guinea pigs developed glaring redness at the bite sites. If this were to work in humans, as the researchers hope, ticks could more quickly be recognized and removed before the bacteria that causes Lyme Disease is transmitted. The results of these guinea pig trials indicate a need to improve 19ISP's vaccine design further or to use it in conjunction with other vaccines or prophylactics.

Vaccines are not the only answer. Dr. Joe Gillespie suggests increased monitoring of deer populations, given that deer herds can drop ticks into new areas or create a higher density of ticks in their existing ranges. “It’s becoming commonplace now for deer to not even run when they see you,” says Joe. “The changing urban landscape is the big problem.” Aerial counts via helicopter or drone, fencing, repellents, and regulated public hunting, are just a few methods for tracking and monitoring deer that have been suggested by The Association of Fish and Wildlife Agencies of North America.

At an even more basic level, we need increased public education, says Dr John Aucott, a clinician at the Johns Hopkins Lyme Disease Clinical Research Center. "Well, when was the last public service announcement you saw for Lyme disease on the news?” he asks. Since ticks need about 30 hours to transmit Lyme Disease, he says that health departments should prioritize increasing awareness of the risk of being out in tick territories. Members of the public along with healthcare providers need to know that what Dr. Aucott says is often confused for a spider bite may very well be a potential Lyme Disease skin reaction.

People should be able to enjoy the outdoors. Still, it is essential to know what is within our control—checking for ticks after hiking or planting in the garden, for instance—until new vaccines or better prophylactics are widely available. Joe thought his first tick bite was just a pimple, and the second time he didn’t see the tick at all. Now he faces the lasting consequences of a poppyseed-sized tick staying attached for too long. "I'm probably not ever going to feel 100 percent. And in the last year, I've accepted that. I'm not ever going to have a normal day."

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